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Influenza outbreaks occur periodically in Long Term Care Facilities (LTCFs) and vaccination is critical in preventing influenza infections. We evaluated the influenza vaccine effectiveness (VE) during respiratory outbreaks in LTCFs reported to the Ministry of Health, Singapore in 2017. A test-negative design was used to estimate the ratio of the odds of testing positive for influenza among vaccinated individuals to the odds among unvaccinated individuals. The VE was calculated as (1-odds ratio) × 100%. For adjusted VE, the estimates were derived using logistic regression adjusted for age group, gender, month of illness, and number of days from date of illness onset till to swab collection date. Estimates by influenza subtypes and post-vaccination time periods (15–180 days & 181–365 days) were also calculated using stratified data. 264 individuals, with 118 laboratory-confirmed influenza cases [32 A(H1N1)pdm09, 75 A(H3N2), 11 A(untypable)], were included in the analysis. No one was identified to be infected with influenza B. The overall adjusted VE estimate was 40.5% (95% CI: −12.2–68.5%), while the subtype-specific adjusted VE estimates were −43.4% (95% CI: −312.4–50.2%) against A(H1N1)pdm09 and 57.1% (95% CI: 5.7–80.5%) against A(H3N2). At 15–180 days post-vaccination period, the adjusted VEs were 59.3% (95% CI: 18.0–79.8%) against all influenza, 35.4% (95% CI: −123.5–81.3%) against A(H1N1)pdm09 and 67.9% (95% CI: 22.5–86.7%) against A(H3N2). Estimates were not significant at 181–365 days post-vaccination. The influenza vaccine showed varying effectiveness among individuals in Singapore’s LTCFs in 2017, with a higher effectiveness among those who were more recently vaccinated. It remains an important tool in preventing influenza infections, especially for those who are at high risk of influenza-related complications.

Aims: In Singapore, pneumococcal vaccination is recommended for the elderly (i.e. those ≥65 years of age) and people with chronic medical conditions. We investigated epidemiological characteristics associated with the uptake of pneumococcal vaccine based on a nationally representative cross-sectional sample of community-living adults aged ≥50 years. Methods: The data were obtained from the National Health Surveillance Survey (NHSS) 2013. Associations between pneumococcal vaccination and sociodemographic and health-related variables were analysed using univariable and multivariable logistic regression models. Results: Among 3672 respondents aged ≥50 years in the NHSS, 7.8% had taken the pneumococcal vaccination. A higher level of education and higher monthly household income were sociodemographic characteristics independently associated with pneumococcal vaccine uptake. Health-related characteristics predictive of pneumococcal vaccine uptake were better self-rated health and having a regular family doctor/general practitioner. Among those who responded to the two questions on vaccinations, 3.9% had been vaccinated against both seasonal influenza and pneumococcal infection, while 11.1% had taken only seasonal influenza vaccination in the past year. Conclusions: There is a need to boost pneumococcal vaccination coverage among community-dwelling older adults. These findings provide insights into reviewing and tailoring public-health strategies and programmes to increase vaccine uptake in at-risk population groups.

Cross-matching of records between Singapore's tuberculosis and HIV registries showed that 3.3% of individuals with tuberculosis (TB) were coinfected with HIV (2000-2014), the TB incidence among individuals with HIV infection was 1.65 per 100 person-years, and 53% of coinfections were diagnosed within 1 month of each other. The findings supported joint prevention programmes for early diagnosis and treatment.

The current study aims to evaluate the burden of disease in Singapore by estimating the quality-adjusted life years (QALYs) lost due to mental disorders and chronic physical conditions. The second Singapore Mental Health Study (SMHS-2016) was conducted in 2016 among 6126 respondents aged 18 years and above. The World Health Organization Composite International Diagnostic Interview version 3.0 (WHO-CIDI 3.0) and a modified version of the CIDI chronic medical disorders checklist were used to assess the 12-month diagnoses of mental and chronic physical disorders while the SF-6D scores derived from the 12-item Short Form Health Survey instrument was used to estimate the QALYs lost. The mean SF-6D score in this population was 0.87. The largest reduction in SF-6D scores among people with mental disorders was observed in Generalized Anxiety Disorder (GAD), followed by Major Depressive Disorder (MDD), alcohol abuse, bipolar disorder and Obsessive Compulsive Disorder (OCD) while the largest reduction in SF-6D score among people with chronic physical conditions was observed in ulcer, followed by lung disease, chronic pain and cardiovascular disease. At the population level, chronic pain was associated with the greatest QALY loss followed by MDD (14,204 and 6,889 respectively). Lung disease was associated with the smallest QALY loss (376). These findings highlight chronic pain, MDD, OCD, cardiovascular disease and GAD as the five leading contributors of QALYs lost in the general population which deserve prioritisation in public health prevention programmes.

Aims The second Singapore Mental Health Study (SMHS) – a nationwide, cross-sectional, epidemiological survey - was initiated in 2016 with the intent of tracking the state of mental health of the general population in Singapore. The study employed the same methodology as the first survey initiated in 2010. The SMHS 2016 aimed to (i) establish the 12-month and lifetime prevalence and correlates of major depressive disorder (MDD), dysthymia, bipolar disorder, generalised anxiety disorder (GAD), obsessive compulsive disorder (OCD) and alcohol use disorder (AUD) (which included alcohol abuse and dependence) and (ii) compare the prevalence of these disorders with reference to data from the SMHS 2010. Methods Door-to-door household surveys were conducted with adult Singapore residents aged 18 years and above from 2016 to 2018 (n = 6126) which yielded a response rate of 69.0%. The subjects were randomly selected using a disproportionate stratified sampling method and assessed using World Health Organization Composite International Diagnostic Interview version 3.0 (WHO-CIDI 3.0). The diagnoses of lifetime and 12-month selected mental disorders including MDD, dysthymia, bipolar disorder, GAD, OCD, and AUD (alcohol abuse and alcohol dependence), were based on the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) criteria. Results The lifetime prevalence of at least one mood, anxiety or alcohol use disorder was 13.9% in the adult population. MDD had the highest lifetime prevalence (6.3%) followed by alcohol abuse (4.1%). The 12-month prevalence of any DSM-IV mental disorders was 6.5%. OCD had the highest 12-month prevalence (2.9%) followed by MDD (2.3%). Lifetime and 12-month prevalence of mental disorders assessed in SMHS 2016 (13.8% and 6.4%) was significantly higher than that in SMHS 2010 (12.0% and 4.4%). A significant increase was observed in the prevalence of lifetime GAD (0.9% to 1.6%) and alcohol abuse (3.1% to 4.1%). The 12-month prevalence of GAD (0.8% vs. 0.4%) and OCD (2.9% vs. 1.1%) was significantly higher in SMHS 2016 as compared to SMHS 2010. Conclusions The high prevalence of OCD and the increase across the two surveys needs to be tackled at a population level both in terms of creating awareness of the disorder and the need for early treatment. Youth emerge as a vulnerable group who are more likely to be associated with mental disorders and thus targeted interventions in this group with a focus on youth friendly and accessible care centres may lead to earlier detection and treatment of mental disorders.

Objective: To assess the public health risk to Singapore posed by the Middle East respiratory syndrome (MERS) outbreak in the Republic of Korea in 2015. Methods: The likelihood of importation of MERS cases and the magnitude of the public health impact in Singapore were assessed to determine overall risk. Literature on the epidemiology and contextual factors associated with MERS coronavirus infection was collected and reviewed. Connectivity between the Republic of Korea and Singapore was analysed. Public health measures implemented by the two countries were reviewed. Results: The epidemiology of the 2015 MERS outbreak in the Republic of Korea remained similar to the MERS outbreaks in Saudi Arabia. In addition, strong infection control and response measures were effective in controlling the outbreak. In view of the air traffic between Singapore and MERS-affected areas, importation of MERS cases into Singapore is possible. Nonetheless, the risk of a serious public health impact to Singapore in the event of an imported case of MERS would be mitigated by its strong health-care system and established infection control practices. Discussion: The MERS outbreak was sparked by an exported case from the Middle East, which remains a concern as the reservoir of infection (thought to be camels) continues to exist in the Middle East, and sporadic cases in the community and outbreaks in health-care settings continue to occur there. This risk assessment highlights the need for Singapore to stay vigilant and to continue enhancing core public health capacities to detect and respond to MERS coronavirus.

Background Adverse childhood experiences (ACEs) are associated with deleterious consequences throughout the lifespan of the individual, including an increased risk of mental disorders. However, an in-depth understanding of ACEs in diverse populations is still lacking especially in Asian populations, with few studies done at a population level. Objective The current study aimed to establish the (i) prevalence of ACEs and its socio-demographic correlates, and, (ii) association of ACEs with mental disorders and suicidality in a multiethnic Asian country. Participants and Setting: Singapore residents aged 18 years and older were recruited from the community as part of a nation-wide cross-sectional epidemiological study. Methods Trained interviewers conducted face-to-face interviews with participants, and administered the Adverse Childhood Experiences – International Questionnaire and the Composite International Diagnostic Interview. Results A total of 6126 participants completed the survey. The lifetime prevalence of ACEs in the sample was 63.9 %. Multiple logistic regression analyses revealed that odds of any ACE were higher among those above 65 years (OR = 1.7) and those without university education (OR = 2.2, 1.9, and 1.5 among those with primary and below, secondary and vocational education respectively). The presence of any ACE was significantly associated with increased odds of mood (OR = 3.7, 95 % CI: 2.3–6.0), anxiety (OR = 3.9, 95 % CI: 2.3–6.8) and alcohol use (OR = 1.7, 95 % CI: 1.1–3.0) disorders. Conclusions ACEs are not uncommon in Asian populations. There is a need to build trauma-informed communities that can incorporate the knowledge of the impact of early trauma into policies and programs.

Singapore is a tropical country with influenza seasons occurring bi-annually. We compared the profile of severely ill patients with laboratory confirmed influenza A(H1N1)pdm09 infection in Singapore during the pandemic and post-pandemic periods, and studied their risk factors associated with mortality.Three periods were defined for this study; pandemic period from 18 June to 29 August 2009, early post-pandemic period from 30 August 2009 to 12 February 2010, and late post-pandemic period from 13 February to 10 August 2010.A total of 172 severely ill patients were admitted to hospitals from 18 June 2009 to 10 August 2010, of whom 23.8% died. The median age in the late post-pandemic period was significantly older than that in the early post-pandemic period (52 years versus 35 years, P=0.02). The median age of patients who died was significantly older than those who survived (52 years versus 44 years, P0.01). The median length of stay under intensive care in the late post-pandemic period was twice that in the early post-pandemic (6 days versus 3 days, P=0.045). The proportion who died in the late post-pandemic period was more than 2.5 times that in the early post-pandemic period (29.8% versus 11.1%, P=0.043).Severely ill patients were of older age in the late post-pandemic period. Older age was also significantly associated with mortality. It is important to maintain heightened vigilance and continue the surveillance of severely ill patients with influenza post-pandemic, so that patients with suspected infections could be promptly identified for early diagnosis and treatment.

Objectives We determined the seroprevalence of chikungunya virus (CHIKV) infection in the adult resident population in Singapore following local outbreaks of chikungunya fever (CHIKF) in 2008–2009. Methods Our cross-sectional study involved residual sera from 3,293 adults aged 18–79 years who had participated in the National Health Survey in 2010. Sera were tested for IgG antibodies against CHIKV and dengue virus (DENV) and neutralizing antibodies against CHIKV. Results The prevalence of CHIKV-neutralizing antibodies among Singapore residents aged 18–79 years was 1.9% (95% confidence interval: 1.4%– 2.3%). The CHIKV seroprevalence was highest in the elderly aged 70–79 years at 11.5%, followed by those aged 30–39 years at 3.1%. Men had significantly higher CHIKV seroprevalence than women (2.5% versus 1.3%, p = 0.01). Among the three main ethnic groups, Indians had the highest seroprevalence (3.5%) compared to Chinese (1.6%) and Malays (0.7%) (p = 0.02 and p = 0.01, respectively). Multivariable logistic regression identified adults aged 30–39 years and 70–79 years, men, those of Indian ethnicity and ethnic minority groups, and residence on ground floor of public and private housing apartments as factors that were significantly associated with a higher likelihood of exposure to CHIKV. The overall prevalence of anti-DENV IgG antibodies was 56.8% (95% CI: 55.1%– 58.5%), while 1.5% (95% CI: 1.1%– 2.0%) of adults possessed both neutralizing antibodies against CHIKV and IgG antibodies against DENV. Conclusions Singapore remains highly susceptible to CHIKV infection. There is a need to maintain a high degree of vigilance through disease surveillance and vector control. Findings from such serological study, when conducted on a regular periodic basis, could supplement surveillance to provide insights on CHIKV circulation in at-risk population., Author summary The prevalence of neutralizing antibodies against chikungunya virus (CHIKV) was low at 1.9% among resident adults in Singapore after local outbreaks in 2008–2009. Adults aged 30–39 years and 70–79 years, men, those of Indian ethnicity and ethnic minority groups, and residence on ground floor of public and private housing apartments were significantly associated with a higher likelihood of exposure to CHIKV.

SUMMARYTo assess the impact of past dengue epidemics in Singapore, we undertook a national seroepidemiological study to determine the prevalence of past dengue virus (DENV) infection in the adult population in 2010 and make comparisons with the seroprevalence in 2004. The study involved residual sera from 3293 adults aged 18–79 years who participated in a national health survey in 2010. The overall prevalence of anti-DENV IgG antibodies was 56·8% (95% confidence interval 55·1–58·5) in 2010. The seroprevalence increased significantly with age. Males had significantly higher seroprevalence than females (61·5%vs.53·2%). Among the three major ethnic groups, Malays had the lowest seroprevalence (50·2%) compared to Chinese (57·0%) and Indians (62·0%). The age-standardized seroprevalence in adults was significantly lower in 2010 (54·4%) compared to 2004 (63·1%). Older age, male gender, Indian ethnicity, permanent residency and being home-bound were independent risk factors significantly associated with seropositivity. About 43% of the Singapore adult resident population remain susceptible to DENV infection as a result of the successful implementation of a comprehensive nationwideAedessurveillance and control programme since the 1970s. Vector suppression and concerted efforts of all stakeholders in the community remain the key strategy in the prevention and control of dengue.

A national pediatric survey was undertaken to determine the prevalence of hepatitis B virus markers in Singapore. The aim was to assess the impact of the national childhood immunization program against hepatitis B implemented for all newborns since 1987. The survey involved prospective collection of residual sera from Singapore residents aged 1–17 years attending inpatient services or day surgery in two public hospitals between August 2008 and July 2010. A total of 1,200 sera were collected comprising 400 in each of the three age groups of 1–6, 7–12, and 13–17 years. The sera were tested for hepatitis B surface antigen (HBsAg) and antibody to HBsAg (anti-HBs). Four of the 1,200 samples tested positive for HBsAg, giving an overall prevalence of 0.3%. One and three in the 7–12 years and 13–17 years age groups, respectively, were positive for HBsAg. About 40% possessed anti-HBs (≥10 mIU/ml); the antibody prevalence decreased significantly from 63.8% in children aged 1–6 years to 32.8% in 7–12 year olds, and 23.5% in 13–17 year olds (P

SUMMARYIn Singapore, influenza vaccination is recommended for persons at higher risk of complications of seasonal influenza, including those with chronic medical conditions and the elderly (individuals aged ⩾65 years). We investigated the factors associated with influenza vaccine uptake based on a nationally representative sample of community-dwelling adults aged >50 years. The data for this study were obtained from the National Health Surveillance Survey (NHSS) 2013. The association between influenza vaccine uptake and socio-demographic and health-related variables was analysed using univariable and multivariable logistic regression models. Of 3700 respondents aged ⩾50 years in the NHSS, 15·2% had received seasonal influenza vaccination in the past year. Older age, single marital status and economic inactivity were the socio-demographic variables independently associated with vaccine uptake. Health-related factors which were predictive of influenza vaccine uptake were sufficient total physical activity, better self-rated health, having at least one medical condition at risk of influenza complications and a regular family doctor/general practitioner. Influenza vaccine uptake in community-dwelling older adults was low. Our findings are of relevance in the formulation of public health policies and targeted health promotion strategies to increase vaccine uptake in this population group.

To determine trends and clinical and epidemiologic features of legionellosis in Singapore, we studied cases reported during 2000–2009. During this period, 238 indigenous and 33 imported cases of legionellosis were reported. Cases were reported individually and sporadically throughout each year. Although the annual incidence of indigenous cases had decreased from 0.46 cases per 100,000 population in 2003 to 0.16 cases per 100,000 in 2009, the proportion of imported cases increased correspondingly from 6.2% during 2000–2004 to 27.3% during 2005–2009 (p

Introduction: We presented the findings from 2 seroprevalence studies conducted 6 years apart, so as to determine changes in the hepatitis B surface antigen (HBsAg) positivity rate and immunity to hepatitis B virus (HBV) among Singapore residents aged 18 to 69 years, and to assess the impact of a 4-year catch-up hepatitis B immunisation programme for adolescents and young adults launched in 2001. Materials and Methods: Two hepatitis B seroprevalence studies (HBSS) were conducted in 1999 and 2005 based on stored blood samples collected from 4698 participants aged 18 to 69 years during the national health survey (NHS) 1998 and from 3460 participants during the NHS 2004, respectively. Serology for HBsAg, hepatitis B e antigen (HBeAg) and antibody to HBsAg (anti-HBs) were tested by enzyme immunoassay in HBSS 1999 and electrochemiluminescence in HBSS 2005. Results: The overall age-standardised prevalence of HBsAg among Singapore residents aged 18 to 69 years decreased significantly from 4.0% in HBSS 1999 to 2.8% in HBSS 2005 (P = 0.002). The age-standardised prevalence of HBsAg in males (4.9% in 1999) and Chinese (4.7% in 1999) both decreased significantly to 2.7% and 2.8%, respectively in 2005. The overall age-standardised population immunity to HBV (anti-HBs >10mIU/ml) increased from 39.7% in 1999 to 42.1% in 2005 (P = 0.019). In particular, the age-specific prevalence of anti-HBs showed a significant increase among those in the age group of 18 to 29 years from 27.9% in 1999 to 41.7% in 2005 (P

Introduction: The objective of the study was to determine the trend of malaria, the epidemiologi-cal characteristics, the frequency of local transmission and the preventive and control measures taken. Materials and Methods: We analysed the epidemiological records of all reported malaria cases maintained by the Communicable Diseases Division, Ministry of Health, from 1983 to 2007 and the Anopheles vector surveillance data collected by the National Environment Agency during the same period. Results: The annual incidence of reported malaria ranged from 2.9 to 11.1 per 100,000 population, with a sharp decline observed after 1997. There were 38 deaths, 92.1% due to falciparum malaria and 7.9% due to vivax malaria. Of the reported cases, 91.4% to 98.3% were imported, with about 90% originating from Southeast Asia and the Indian sub-continent. Among the various population groups with imported malaria, the proportion of cases involving work permit/employment pass holders had increased, while that of local residents had decreased. Between 74.8% and 95.1% of the local residents with imported malaria did not take personal chemoprophylaxis when they travelled overseas. Despite the extremely low Anopheles vector population, a total of 29 local outbreaks involving 196 cases occurred. Most of the larger outbreaks could be traced to foreign workers with imported relapsing vivax malaria and who did not seek medical treatment early. One of the outbreaks of 3 cases in 2007 was caused by Plasmodium knowlesi, a newly recognised simian malaria which was probably acquired in a forested area where long-tail macaques had been sighted. Conclusions: Singapore remains both vulnerable and receptive to the reintroduction of malaria and a high level of vigilance should be maintained indefinitely to prevent the re-establishment of endemicity. Medical practitioners should highlight the risk of malaria to travellers visiting endemic areas and also consider the possibility of simian malaria in a patient who has no recent travel history and presenting with daily fever spikes and with malaria parasite morphologically similar to that of P. malariae. Key words: Anopheles mosquitoes, Foreign workers, Outbreaks, Simian malaria

Introduction: To determine the seroepidemiology of dengue virus infection in a representative sample of the adult resident population aged 18 years old to 74 years old in Singapore and to estimate the proportion of asymptomatic dengue infection during the 2004 epidemic. Materials and Methods: The study was based on 4152 stored blood samples collected between September and December 2004 from participants aged 18 years old to 74 years old during the 2004 National Health Survey. Sera were tested for IgG and IgM antibodies using a commercial test kit (PanBio Capture/Indirect ELISA). Results: Of the study population, 59.0% and 2.6% tested positive for dengue IgG (past infection) and IgM/high-titre IgG (recent infection), respectively. Only 17.2% of young adults aged 18 years old to 24 years old were dengue IgG positive. Multivariate analyses showed that older age, Indian ethnicity and male gender were significantly associated with past infection, whereas only age was significantly associated with recent dengue infection. Based on the dengue cases notified during the period of survey, it was estimated that for every 23 individuals recently infected with dengue, only 1 was reported to the health authority as a clinical case. Conclusion: The Singapore population is highly susceptible to dengue epidemics despite its aggressive Aedes prevention and control programme. The finding of a high proportion of unreported cases due to asymptomatic and subclinical infection poses a challenge for dengue control. Key words: Aedes control, Asymptomatic infection, Herd immunity

We conducted a pediatric seroprevalence study of dengue virus (DENV) infection in Singapore, a dengue endemic city-state. Residual sera from 1,200 Singapore residents aged 1-17 years seen in two hospitals between 2008 and 2010 were tested for anti-DENV IgG antibodies. The overall seroprevalence was 10.4% (95%CI: 8.7-12.1%). There had been a marked decline in seroprevalence in the 15-19-year age group over the last three decades, while the prevalence in the 1-5-year olds (12.6%) was significantly higher than that of the 1996-1997 pediatric survey (0.8%). The overall dengue seroprevalence in children and adolescents remained low.

BACKGROUND In view of waning antitoxin titres over time after the last vaccine dose against diphtheria and tetanus, we determined the immunity levels in adults to identify most susceptible groups for protection in Singapore. METHODS Our study involved residual sera from 3293 adults aged 18-79 who had participated in a national health survey in 2010. IgG antibody levels were determined using commercial enzyme-linked immunosorbent assay. RESULTS Overall, 92.0% (95% confidence interval [CI]: 91.1-92.9%) had at least basic protection against diphtheria (antibody levels ≥0.01 IU/ml), while 71.4% (95% CI: 69.8-72.9%) had at least short-term protection against tetanus (antibody levels >0.1 IU/ml). The seroprevalence declined significantly with age for both diseases; the drop was most marked in the 50- to 59-year age group for diphtheria and 60- to 69-year age group for tetanus. There was a significant difference in seroprevalence by residency for diphtheria (92.8% among Singapore citizens versus 87.1% among permanent residents; P = 0.001). The seroprevalence for tetanus was significantly higher among males (83.2%) than females (62.4%) (P < 0.0005). CONCLUSIONS It may be of value to consider additional vaccination efforts to protect older adults at higher risk for exposure against diphtheria and tetanus, particularly those travelling to areas where diphtheria is endemic or epidemic.

Objective In line with regional and global goals for the elimination of rubella and congenital rubella syndrome (CRS), we reviewed the epidemiological situation in Singapore, based on surveillance reports on rubella and CRS, national immunization coverage and seroprevalence surveys. The aim of our review was to identify current gaps and steps taken to achieve the targets set by the World Health Organization (WHO) Western Pacific Regional Office (WPRO). Methods Epidemiological data on clinical and laboratory-confirmed rubella cases, including CRS, notified to the Communicable Diseases Division, Ministry of Health, Singapore, from 2003 to 2013 were collated and analyzed. Vaccination coverage against rubella was obtained from the National Immunization Registry and School Health Services of the Health Promotion Board. The changing prevalence of rubella was determined from periodic serological surveys. Findings The incidence of indigenous rubella cases per million population decreased from 37.2 in 2008 to 7.6 in 2013 and there had been no indigenous case of CRS in 2012 and 2013. Therapeutic abortions performed due to rubella infections had become uncommon. The annual measles, mumps, and rubella (MMR) vaccination coverage in childhood population remained high ranging from 93% to 96%. The overall susceptibility to rubella in women aged 18–44 years had reduced significantly from 15.8% in 2004 to 11.0% in 2010. The prevalence of IgG antibody against rubella among Singapore children aged 1–17 years was maintained at 87.3% in 2008–2010. Conclusion All available data indicated that Singapore has made good progress towards the elimination of rubella and CRS. It has attained the targets set by the WHO WPRO for 2015. In preparation for verification of rubella elimination, an enhanced surveillance system has been implemented to ensure that all reported cases are laboratory confirmed, and genotyping of rubella virus strains isolated is carried out to provide evidence for interruption of endemic transmission.

Coxsackieviruses A6 (CV-A6) and A16 (CV-A16) and Enterovirus 71 (EV-A71) have caused periodic epidemics of hand, foot and mouth disease (HFMD) among children in Singapore. We conducted a cross-sectional study to estimate the seroprevalence of these enteroviruses among Singapore children and adolescents. The study was conducted between August 2008 and July 2010. It involved 700 Singapore residents aged 1–17 years whose residual sera were obtained following the completion of routine biochemical investigations in two public acute-care hospitals. The levels of neutralizing antibodies (NtAb) against CV-A6, CV-A16 and EV-A71 were analyzed by the microneutralization test. The age-specific geometric mean titer (GMT) of antibodies against each of the three enteroviruses and the 95% confidence intervals (CI) were calculated. The seroprevalence of CV-A6 and CV-A16 was high at 62.7% (95% CI: 59.1–66.2%) and 60.6% (95% CI: 56.9–64.1%), respectively. However, the seroprevalence of EV-A71 was significantly lower at 29.3% (95% CI: 26.0–32.8%). About 89.7% of the children and adolescents had been infected by at least one of the three enteroviruses by 13–17 years of age. About half (52.3%) were seropositive for two or all three enteroviruses, while only 16.1% had no NtAb against any of the three enteroviruses. High NtAb levels were observed in the younger age groups. CV-A6 and CV-A16 infections are very common among Singapore children and adolescents, while EV-A71 infections are less common. Infection is continually acquired from early childhood to adolescent age.

The aim of this study was to compare the demographic and clinical characteristics of pregnant women and non-pregnant women of childbearing age hospitalized with laboratory-confirmed influenza A(H1N1)pdm09 infection in Singapore, and to assess whether pregnancy was a risk factor associated with the development of influenza-related complications.Retrospective observational study.We retrospectively identified and collected information from available medical records of all women admitted to three tertiary hospitals between 26 May 2009 and 31 December 2009 with laboratory-confirmed influenza A(H1N1)pdm09 infection who were either pregnant or non-pregnant and of childbearing age between 15 and 50 years.A total of 222 women, of whom 81 (36.5%) were pregnant, were hospitalized during the study period. Pregnant women were significantly more likely to be hospitalized with influenza A(H1N1)pdm09 infection than non-pregnant women of childbearing age (relative risk 26.3; 95% confidence interval: 20.1-34.6). Among those hospitalized, the proportion of pregnant women having at least one underlying medical condition that could predispose them to influenza-related complications was significantly lower than that of non-pregnant women (32.1% versus 56.0%, P0.001). The median time from onset of symptoms to administration of anti-viral drugs was significantly shorter among pregnant women than among non-pregnant women (three days versus five days, P0.001). The median length of stay in hospital was also significantly shorter among pregnant women than that of non-pregnant women (two days versus three days, P = 0.002). About 4.9% of pregnant women developed influenza-related complications, compared with 12.8% among non-pregnant women (P = 0.066).Pregnant women with influenza A(H1N1)pdm09 infection were at a higher risk of hospitalization. Upon hospitalization, they were not at a higher risk of developing influenza-related complications.

The incidence of melioidosis in Singapore decreased during 1998-2007, with the exception of the first quarter of 2004. After heavy rainfalls, an increase in pneumonic cases with a high case-fatality rate was detected. We show that melioidosis has the potential to reemerge following adverse climate events.

We undertook a national hepatitis B seroprevalence study to assess the seroprevalence of hepatitis B virus (HBV) markers in the adult population in Singapore in 2010 and make comparisons with the seroprevalence in 1998 and 2004. The study involved residual sera from national health surveys conducted every six years since 1998. The tests for HBV markers were carried out using commercial chemiluminescent microparticle immunoassay. In 2010, the prevalence of hepatitis B surface antigen (HBsAg) among 3293 Singapore residents aged 18-79 years was 3.6% (95% confidence interval [CI] 2.9-4.2%). Hepatitis B e antigen (HBeAg) was detected in 4.2% of those who were HBsAg positive. About 22.5% (95% CI 21.1-23.9%) were positive for antibody to hepatitis B core antigen (anti-HBc). The overall population immunity to HBV, as determined by antibody to hepatitis B surface antigen (anti-HBs)≥ 10 mIU/mL, was 43.9% (95% CI 42.2-45.6%). Among young adults below 30 years of age, HBsAg prevalence (1.1%) was half that in 1998 and 2004, and in those positive for HBsAg, none was positive for HBeAg in 2010, compared to 20.8% in 1998 and 15.8% in 2004. In this age group, anti-HBc prevalence also decreased significantly from 22.1% in 2004 to 4.4% in 2010, while anti-HBs (≥ 10 mIU/mL) prevalence increased significantly from 27.9% in 1998 to 43.3% in 2010 (p

SUMMARYWe undertook a national paediatric seroprevalence survey of measles, mumps and rubella (MMR) in Singapore to assess the impact of the national childhood immunization programme against these three diseases after introduction of the trivalent MMR vaccine in 1990. The survey involved 1200 residual sera of Singapore residents aged 1–17 years collected from two hospitals between 2008 and 2010. The overall prevalence of antibodies against measles, mumps and rubella was 83·1% [95% confidence interval (CI) 80·9–85·1], 71·8% (95% CI 69·1–74·2) and 88·5% (95% CI 86·6–90·2), respectively. For all three diseases, the lowest prevalence was in children aged 1 year (47·8–62·3%). The seroprevalence of the vaccinated children declined over time. The national MMR immunization programme is effective in raising the herd immunity of the childhood population, although certain age groups are more susceptible to infection, in particular, those who are not eligible for vaccination at age

The delay in HIV diagnosis has been identified as a significant reason for late presentation to medical care. This research aims to elucidate the significant determinants of late-stage HIV infection in Singapore between 1996 and 2009, after the advent of highly active anti-retroviral therapies.We included 3735 patients infected via sexual mode of transmission from the National HIV Registry diagnosed between 1996 and 2009. Late-stage HIV infection is defined as CD4 count less than 200 mm(3) or AIDS-defining opportunistic infections at fi rst diagnosis or within one year of HIV diagnosis. We determined independent epidemiological risk factors for late-stage HIV infection at first diagnosis using multivariate logistic regression.Multivariate analysis showed that older age corresponded significantly with increasing odds of late-stage HIV infection. Compared to persons diagnosed at 15 to 24 years of age, those diagnosed at age 55 years and above were associated with 5-fold increased likelihood of late-stage infection (adjusted odds ratio (AOR): 5.17; 95% CI, 3.21 to 8.33). Chinese ethnicity, singlehood, and non-professional occupations were also significantly associated with late-stage HIV infection. Persons detected in the course of medical care had over 3.5 times the odds of late-stage infection (AOR: 3.55; 95% CI, 2.71 to 4.65). Heterosexual mode of transmission and having sex workers and social escorts as sexual partners, were the other epidemiological risk factors with significant associations.The findings of this study emphasises the need to increase HIV awareness and to encourage early and regular HIV testing among at-risk persons.

Introduction: Singapore has experienced remarkable socioeconomic progress over the last few decades, with a corresponding rise in standards of sanitation and living conditions. We undertook a study to describe its epidemiological trends of hepatitis A over the last 2 decades. Materials and Methods: We analysed the epidemiological data on all laboratory-confirmed cases of hepatitis A from 1990 to 2009. We also described 3 outbreaks which occurred in 1991, 1992 and 2002. To determine the changing prevalence of hepatitis A virus (HAV) infection, we compared the findings from a seroepidemiological study conducted in 1993 with earlier surveys in 1975 and 1984/1985. Results: The incidence of indigenous hepatitis A cases per 100,000 population declined significantly from 1.8 in 1989 to 0.7 in 2009, and more than half were imported. While majority of the imported cases were Singapore residents, the proportion of imported cases among Singapore residents had decreased significantly. Most of the Singapore residents contracted the disease from Southeast Asia and the Indian subcontinent. The overall prevalence of HAV infection in the population declined from 31.8% in 1984/85 to 25.9% in 1993. Conclusion: The incidence and seroprevalence of hepatitis A in Singapore are comparable to other developed countries. As Singapore is situated in a region highly endemic for HAV, it is very vulnerable to the introduction of the disease because of the high volume of regional travel and import of food, especially shellfish. While we note that there have been no further shellfish-associated outbreaks since 2002, sustained vigilance, strict control of food import by the authorities and public health education on the risk of consuming shellfish, especially cockles, raw and half-cooked, should be maintained. Key words: Cockles, Imported cases, Outbreaks, Oysters, Shellfish, Seroprevalence

Introduction: We studied the epidemiological trends of enteric fevers (typhoid and paratyphoid fever) in Singapore from 1990 to 2009 and carried out a review of the current prevention and control measures. Materials and Methods: Epidemiological records of all reported enteric fevers maintained by the Communicable Diseases Division, Ministry of Health from 1990 to 2009 were analysed. Results: A total of 2464 laboratory confirmed cases of enteric fevers (1699 cases of typhoid and 765 cases of paratyphoid) were reported. Of these, 75% were imported, mainly from India and Indonesia. There had been a significant fall in the mean annual incidence rate of indigenous enteric fevers from 4.3 per 100,000 population in 1990 to 0.26 per 100,000 population in 2009 (P

Summary Objectives We conducted an epidemiological review of the chikungunya fever situation in Singapore and described the measures taken to prevent the chikungunya virus from becoming entrenched in the tropical city-state. Methods All laboratory-confirmed cases and outbreak investigation reports maintained by the Communicable Diseases Division, Ministry of Health, and Aedes mosquito surveillance data obtained by the National Environment Agency during the period 2006 and 2009 were reviewed and analysed. Results Sporadic cases were imported into Singapore until the first local transmission occurred in an urban area where Aedes aegypti was the predominant vector. Subsequent introduction of a mutant viral strain (A226V) in early 2008 resulted in the rapid spread to suburban and rural areas where Aedes albopictus was the primary vector. 1072 cases including 812 (75.7%) indigenous cases were reported. The main sources of importation were India and Malaysia. Foreign contract workers were identified as high-risk for indigenous infections. Conclusions The disease was successfully brought under control through aggressive vector control measures directed at A. albopictus . Although the incidence has sharply declined since January 2009, a high degree of vigilance is maintained to prevent a recurrence of epidemic transmission which can occur even with a well-established nationwide mosquito control programme.

Introduction: Singapore’s defense against imported novel influenza A (H1N1-2009) comprised public health measures in compliance with the World Health Organization’s (WHO) International Health Regulations (IHR), 2005. We report herein on the epidemiology and control of the first 350 cases notified between May and June 2009. Materials and Methods: We investigated the first 350 laboratory-confirmed cases of novel influenza A (H1N1-2009) identified from the healthcare institutions between 27 May and 25 June 2009. Epidemiological details of these cases were retrieved and analysed. Contact tracing and active case finding were also instituted for each reported case, and relevant particulars including flight information were provided to WHO and overseas counterparts. Results: The first 350 novel influenza A (H1N1-2009) cases comprised 221(63%) imported cases, 124 (35%) locally acquired cases and 5 (2%) cases with unknown source. The imported cases consisted of three waves involving the United States (US), Australia and Southeast Asia. In the first wave, 11 (69%) of the 16 imported cases had visited the US within seven days prior to their onset of illness between 25 May and 4 June 2009. In the second wave, 20 (74%) of the 27 imported cases between 5 June and 12 June had travelled to Melbourne, Australia. In the third wave, 90 (51%) of the 178 imported cases between 13 June and 25 June were acquired from intra-regional travel in Southeast Asia. Specifically, 49 cases were from the Philippines and 40 (82%) of them had travelled to Manila. A total of 667 communications were effected through the IHR mechanism; a majority within 24 hours of disease notification. Conclusion: Singapore experienced an unprecedented need for international co-operation in surveillance and response to this novel Influenza A (H1N1-2009) pandemic. The IHR mechanism served as a useful channel to engage in regional cooperation concerning disease surveillance and data sharing, but requires improvement. Key words: Cooperation, Imported, Influenza A (H1N1-2009), Transmission

We reviewed the epidemiological features of 1348 hospitalised cases of influenza A (H1N1-2009) [pandemic H1N1] infection in Singapore reported between 15 July and 28 September 2009.Data on the demographic and epidemiological characteristics of hospitalised patients with confirmed pandemic H1N1 infection were collected from all restructured and private hospitals in Singapore using a standard template and were analysed retrospectively.Of the 1348 cases, 92 were classified as severely ill (i.e. were admitted to an intensive care unit and/or who died). Of these severely ill cases, 50 (54.3%) required mechanical ventilation. While overall hospitalisation rates were highest in the 0 to 11 months age group, the incidence of severely ill cases was highest in patients aged 65 years and older. Fifty per cent of all hospitalised cases and 28% of all severely ill cases did not have any underlying medical conditions. The following factors were found to be independently associated with a higher likelihood of severe illness: older age and the presence of the following comorbidities: neuromuscular disorders, epilepsy and obesity.Between 15 July and 28 September 2009, pandemic H1N1 infection caused significant illness requiring hospitalisation, as well as intensive care and mechanical ventilation in some cases. There were 18 deaths from pandemic H1N1 during this period, which corresponded to a case-fatality rate of 7 deaths for every 100,000 cases of pandemic H1N1.

The fi rst case of pandemic influenza A(H1N1) was detected in Singapore on 26 May 2009, 1 month after the fi rst cases of novel influenza A(H1N1) was reported in California and Texas in the United States. The World Health Organization declared the fi rst influenza pandemic of the 21st century on 11 June 2009.Confirmed cases notified to the Ministry of Health between 27 May and 9 July 2009 were analysed. Various indicators of influenza activity were monitored throughout the study period. Estimates of the number of cases of H1N1-2009 were made using the number of polyclinic attendances for acute respiratory infection and influenza-like illness and the weekly prevalence of H1N1-2009.Cases in Singapore affected mainly young adults, youths and children. By the end of September 2009, it was estimated that at least 270,000 persons had been infected by pandemic influenza A (H1N1) in Singapore. The peak number of cases occurred during E-week 30 (26 July-1 August) when an estimated 45,000 cases were seen in polyclinics and GP clinics. The hospitalisation, severe illness and mortality rates were estimated at 6 per 1000 cases, 0.3 per 1000 cases and 6.7 per 100,000 cases, respectively. The most common risk factors among hospitalised adult cases were asthma and diabetes. For hospitalised children, the most common risk factors were being under 5 years of age and asthma. The most common risk factors among persons with severe illness were diabetes in adults and epilepsy and being under 5 years of age in children. About half of cases with severe illness required mechanical ventilation. In addition, one-fifth of cases with severe illness had acute respiratory distress syndrome.The fi rst wave of the influenza pandemic lasted about 10 weeks. Morbidity and mortality resulting from pandemic influenza were low.

Introduction: We reviewed the epidemiological features of rubella in Singapore and the impact of the national immunisation programme in raising the population herd immunity against rubella, with special reference to females in the reproductive age group, and in the elimination of congenital rubella syndrome (CRS). Materials and Methods: Epidemiological data on all reported cases of rubella and CRS were obtained from the Communicable Diseases Division and Central Claims Processing System, respectively, at the Ministry of Health. Coverage of the childhood immunisation programme against rubella was based on the immunisation data maintained by the National Immunisation Registry, Health Promotion Board. To assess the herd immunity of the population against rubella, 4 serological surveys were conducted from 1989 to 1990, in 1993, 1998 and 2004. Results: The incidence of rubella has decreased significantly from the peak of 13.3 per 100,000 population in 1996 to 1.8 per 100,000 in 2007. CRS has virtually disappeared. With more than 92% to 93% of primary school leavers and preschool children annually vaccinated against rubella since 1976 and 1990, respectively, the level of susceptibility to rubella among women in the reproductive age group has gradually decreased from 44% in 1975 to 28% in 1985, and maintained at between 10% and 20% from 1987 to 1998. A considerable proportion (15.8%) of women 18 to 44 years of age remained susceptible to rubella infection in 2004. Conclusion: Rubella prevention and control has been successfully implemented. However, the relatively high level of susceptibility to rubella among women in the reproductive age group continues to be of concern. More public awareness and health educational efforts are needed and every opportunity should be taken to ensure that all susceptible women are identified and protected against the infection. Key words: Congenital rubella syndrome, Immunisation, Serological surveys

Introduction: We reviewed the epidemiology of hand, foot and mouth disease (HFMD) in Singapore after the 2000 epidemic caused by Enterovirus 71 (EV71), with particular reference to the cyclical pattern, predominant circulating enteroviruses and impact of prevention and control measures in preschool centres. Materials and Methods: We analysed the epidemiological data from all clinical cases and deaths of HFMD diagnosed by medical practitioners and notified to the Ministry of Health, as well as laboratory data on enteroviruses detected among HFMD patients maintained by the Department of Pathology, Singapore General Hospital, and the Microbiology Laboratory, KK Women’s and Children’s Hospital from 2001 to 2007. Results: The incidence rate was highest in the 0 to 4 years old age group, with males being predominant. Three deaths were reported between January and February 2001. Nationwide epidemics occurred periodically; the predominating circulating virus was Coxsackievirus A16 (CA16) in the 2002, 2005 and 2007 epidemics, and EV71 in the 2006 epidemic. During the epidemic years between 2005 and 2007, 2 peaks were observed. The number of institutional outbreaks had increased 10-fold from 167 in 2001 to 1723 in 2007, although most of these outbreaks were rapidly brought under control with an attack rate of less than 10%. Conclusion: HFMD remains an important public health problem in Singapore with the annual incidence rate per 100,000 population increasing from 125.5 in 2001 to 435.9 in 2007, despite stringent measures taken in preschool centres to prevent the transmission of infection. A high degree of vigilance should be maintained over the disease situation, in particular, surveillance of EV 71 which continues to cause severe complications and deaths in the region. Key words: Coxsackievirus A16, Enterovirus 71, Epidemic, Preschools

Introduction: We investigated the 2005 outbreak of dengue fever (DF)/dengue haemorrhagic fever (DHF) to determine its epidemiological, virological and entomological features to further understand the unprecedented resurgence. Materials and Methods: All physician-diagnosed, laboratory-confirmed cases of DF/DHF notified to the Ministry of Health, Singapore during the outbreak as well as entomological and virological data were analysed retrospectively. Results: A total of 14,006 cases of DF/DHF comprising 13,625 cases of DF and 381 cases of DHF, including 27 deaths were reported, giving an incidence rate of 322.6 per 100,000 and a case-fatality rate of 0.19%. The median age of the cases and deaths were 32 and 59.5 years, respectively. The incidence rate of those living in compound houses was more than twice that of residents living in public and private apartments. The distribution of DF/DHF cases was more closely associated with Aedes aegypti compared to Aedes albopictus breeding sites and the overall Aedes premises index was 1.15% (2.28% in compound houses and 0.33% to 0.8% in public and private apartments). The predominant dengue serotype was DEN-1. A significant correlation between weekly mean temperature and cases was noted. The correlation was strongest when the increase in temperature preceded rise in cases by a period of 18 weeks. Conclusion: The resurgence occurred in a highly densely populated city-state in the presence of low Aedes mosquito population. Factors contributing to this resurgence included lower herd immunity and change in dominant dengue serotype from DEN-2 to DEN-1. There was no evidence from gene sequencing of the dengue viruses that the epidemic was precipitated by the introduction of a new virulent strain. The current epidemiological situation is highly conducive to periodic dengue resurgences. A high degree of vigilance and active community participation in source reduction should be maintained. Key words: Dengue haemorrhagic fever, Dengue fever, Outbreak

Objective:Methicillin-resistant Staphylococcus aureus (MRSA) strains have emerged in the community, causing disease among healthy people lacking traditional risk factors for MRSA infection. This article describes an outbreak of MRSA among healthy full-term newborns.Design:Cases were identified and corresponding medical information collected. Telephone interviews were conducted with mothers of cases ands surveillance cultures from mothers and newborns were performed. MRSA isolates were genotyped.Setting:Hospital in Chicago, Illinois, USA.Participants:Newborns, their mothers and hospital healthcare workers.Intervention:Nursery infection control practices were enhanced. The MRSA-colonised healthcare workers received intranasal mupirocin.Main outcome:Within 4–23 days of birth, 11 newborns were identified with pustules, vesicles or blisters located on the head, groin, perineum, ears, legs, chin and trunk. All received antimicrobials and recovered without incident.Results:None of 432 peripartum women, one of 399 newborns, and two of 135 healthcare workers were nasal MRSA carriers. Available isolates from six patients, two healthcare workers, and one from an MRSA-colonised newborn were similar by pulsed-field gel electrophoresis. Other than contact with the hospital, no common exposures of MRSA transmission were identified.Conclusions:MRSA strains that initially emerged in the community are now causing disease in healthcare settings. Providers should be aware that MRSA can cause skin infections among healthy newborns. Adherence to standard infection control practices is important to prevent transmission of MRSA in nurseries.

The first case of HIV infection in Singapore was reported in 1985. Between 1991 and 1998, the number of reported cases of HIV and AIDS increased rapidly before stabilizing from 1999. The epidemiology of the AIDS epidemic in Singapore is characterized by a predominance of male cases (seven to one) and heterosexual transmission. A multipronged control program comprising public education and education of high-risk groups, legislation, protection of the national blood supply, management of cases, and epidemiological surveillance has been put in place. The promotion of condom use among local sex workers has been fairly successful, with very low rates of HIV and other sexually transmitted infections (STIs). However, freelance and potential indirect sex workers such as masseuses and lounge hostesses are a concern in view of their higher prevalence of HIV and STIs. Another concern is the high proportion of cases who are diagnosed only when they develop AIDS. A better understanding of sexual networks among men who have sex with men will enable more effective intervention programs for this group. Fresh innovative approaches are needed to encourage safe sex practices and early screening.