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The epidemiology of H5N1 and H7N9 avian viruses of humans infected in China differs despite both viruses being avian reassortants that have inherited six internal genes from a common ancestor, H9N2. The median age of infected populations is substantially younger for H5N1 virus (26 years) compared with H7N9 virus (63 years). Population susceptibility to infection with seasonal influenza is understood to be influenced by cross-reactive CD8+ T cells directed towards immunogenic peptides derived from internal viral proteins which may provide some level of protection against further influenza infection. Prior exposure to seasonal influenza peptides may influence the age-related infection patterns observed for H5N1 and H7N9 viruses. A comparison of relatedness of immunogenic peptides between historical human strains and the two avian emerged viruses was undertaken for a possible explanation in the differences in age incidence observed. There appeared to be some relationship between past exposure to related peptides and the lower number of H5N1 virus cases in older populations, however the relationship between prior exposure and older populations among H7N9 virus patients was less clear.

We reviewed key attributes (flexibility, data quality and timeliness) of Australia's National Notifiable Diseases Surveillance System (NNDSS) over its first 21 years. Cases notified to NNDSS from 1991 to 2011 were examined by jurisdiction (six states and two territories) and sub-period to describe changes in the number of notifiable diseases, proportion of cases diagnosed using PCR tests, data quality (focusing on data completeness), and notification delays. The number of notifiable diseases increased from 37 to 65. The proportion of cases diagnosed by PCR increased from 1% (1991-1997) to 49% (2005-2011). Indigenous status was complete for only 44% notifications (jurisdictional range 19-87%). Vaccination status was complete for 62% (jurisdictional range 32-100%) and country of acquisition for 24% of relevant cases. Data completeness improved over the study period with the exception of onset date. Median time to notification was 8 days (interquartile range 4-17 days, jurisdictional range 5-15 days); this decreased from 11 days (1991-1997) to 5 days (2005-2011). NNDSS expanded during the study period. Data completeness and timeliness improved, likely related to mandatory laboratory reporting and electronic data transfer. A nationally integrated electronic surveillance system, including electronic laboratory reporting, would further improve infectious disease surveillance in Australia.

Overwhelming post-splenectomy infection (OPSI) is a serious complication of asplenia and is associated with encapsulated organisms, most commonly Streptococcus pneumoniae, but also Haemophilus influenzae and Neisseria meningitidis. We aimed to estimate the risk of infection in this patient group. We reviewed data collected by the Victorian Spleen Registry in Australia. On registration, all patients are asked about significant infections requiring admission to hospital for intravenous antibiotics; those requiring admission to ICU were defined as OPSI. In the 3274 asplenic patients registered 492 patients reported at least one episode of infection. There were 47 episodes of OPSI requiring intensive care (incidence rate 1·11/1000 patient-years). The risk of OPSI was highest in older patients, and there were no statistically significant differences in incidence by reason for splenectomy except for a higher rate in patients with medical hyposplenia. This study reinforces that post-splenectomy infection is a clinically significant but uncommon complication, and that fulminant infection requiring intensive care is a minority of all infections.

We reviewed the first 21 years (1991-2011) of Australia's National Notifiable Diseases Surveillance System (NNDSS). All nationally notified diseases (except HIV/AIDS and Creutzfeldt-Jakob disease) were analysed by disease group (n = 8), jurisdiction (six states and two territories), Indigenous status, age group and notification year. In total, 2 421 134 cases were analysed. The 10 diseases with highest notification incidence (chlamydial infection, campylobacteriosis, varicella zoster, hepatitis C, influenza, pertussis, salmonellosis, hepatitis B, gonococcal infection, and Ross River virus infection) comprised 88% of all notifications. Annual notification incidence was 591 cases/100 000, highest in the Northern Territory (2598/100 000) and in children aged <5 years (698/100 000). A total of 8·4% of cases were Indigenous Australians. Notification incidence increased by 6·4% per year (12% for sexually transmissible infections and 15% for vaccine-preventable diseases). The number of notifiable diseases also increased from 37 to 65. The number and incidence of notifications increased throughout the study period, partly due to addition of diseases to the NNDSS and increasing availability of sensitive diagnostic tests. The most commonly notified diseases require a range of public health responses addressing high-risk sexual and drug-use behaviours, food safety and immunization. Our results highlight populations with higher notification incidence that might require tailored public health interventions.

To identify hospital-level factors associated with post-cardiac surgical pneumonia for assessing their impact on standardized infection rates (SIRs), we studied 43 691 patients in a cardiac surgery registry (2001-2011) in 16 hospitals. In a logistic regression model for pneumonia following cardiac surgery, associations with hospital characteristics were quantified with adjustment for patient characteristics while allowing for clustering of patients by hospital. Pneumonia rates varied from 0·7% to 12·4% across hospitals. Seventy percent of variability in the pneumonia rate was attributable to differences in hospitals in their long-term rates with the remainder attributable to within-hospital differences in rates over time. After adjusting for patient characteristics, the pneumonia rate was found to be higher in hospitals with more registered nurses (RNs)/100 intensive-care unit (ICU) admissions [adjusted odds ratio (aOR) 1·2, P = 0·006] and more RNs/available ICU beds (aOR 1·4, P < 0·001). Other hospital characteristics had no significant association with pneumonia. SIRs calculated on the basis of patient characteristics alone differed substantially from the same rates calculated on the basis of patient characteristics and the hospital characteristic of RNs/100 ICU admissions. Since SIRs using patient case-mix information are important for comparing rates between hospitals, the additional allowance for hospital characteristics can impact significantly on how hospitals compare.

The generalizability of a prediction model from North America for incident nosocomial pneumonia following coronary artery bypass graft surgery was assessed for 23247 patients on the Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) registry. The performance of the North American model was evaluated using measures of calibration and discrimination. The model had reasonable discrimination (area under the receiver-operating characteristic curve, AUC=0·69), but unsatisfactory calibration (Hosmer-Lemeshow test, P<0·001) in the ANZSCTS patients. An update of the model coefficients yielded a model with AUC=0·71 and good calibration (P=0·46).

This nested case-control study investigated the risk factors for gastroenteritis in a cohort using rainwater as their primary domestic water source. Consumption of beef [odds ratio (OR) 2·74, 95% confidence interval (CI) 1·56-4·80], handling of raw fresh chicken in the household (OR 1·52, 95% CI 1·02-2·29) and animal contact (OR 1·83, 95% CI 1·20-2·83) were found to be significant risk factors (P>0·05). Significant protective effects were observed with raw salad prepared at home (OR 0·33, 95% CI 0·18-0·58), consumption of salami (OR 0·60, 95% CI 0·36-0·98), and shellfish (OR 0·31, 95% CI 0·14-0·67). This study provides novel insight into community-based endemic gastroenteritis showing that consumption of beef was associated with increased odds of illness and with a population attributable fraction (PAF) of 57·6%. Detecting such a high PAF for beef in a non-outbreak setting was unexpected.

Surveillance for gastroenteritis rarely detects small, intra-familial outbreaks. This study examined intra-household transmission of gastroenteritis using prospectively collected data from 2811 participants (600 households) in a community-based study. There were 258 household clusters of gastroenteritis during the 15 months of observation involving 774 residents (28% of total). Age <6 years and attendance at a day care/kindergarten were associated with increased likelihood of inclusion in a cluster. The reach of illness into the household was extensive, with 63% of household members affected by symptoms during clusters. Simultaneous and secondary transmission of gastroenteritis appeared equally common. In only 20% of clusters did more than one member submit a faecal specimen. Of clusters where two or more specimens were submitted, concordance in laboratory confirmation of pathogens was 18.8%. Our results show that clustering of gastrointestinal symptoms within households occurs commonly, but reliance on pathogen notification data will substantially underestimate the true frequency of gastroenteritis clusters.

Objective: To analyze the risk factors for surgical site infection (SSI) complicating coronary artery bypass graft (CABG) surgery and to create an alternative SSI risk score based on the results of multivariate analysis., Methods: A prospective cohort study involving inpatient and laboratory-based surveillance of patients who underwent CABG surgery over a 27-month period from January 1, 2003 through March 31, 2005. Data were obtained from 6 acute care hospitals in Victoria, Australia, that contributed surveillance data for SSI complicating CABG surgery to the Victorian Hospital Acquired Infection Surveillance System Coordinating Centre and the Australasian Society of Cardiac and Thoracic Surgeons, also in Victoria., Results: A total of 4,633 (93%) of the 4,987 patients who underwent CABG surgery during this period were matched in the 2 systems databases. There were 286 SSIs and 62 deep or organ space sternal SSIs (deep or organ space sternal SSI rate, 1.33%). Univariate analysis revealed that diabetes mellitus, body mass index (BMI) greater than 35, and receipt of blood transfusion were risk factors for all types of SSI complicating CABG surgery. Six multivariate analysis models were created to examine either preoperative factors alone or preoperative factors combined with operative factors. All models revealed diabetes and BMI of 30 or greater as risk factors for SSI complicating CABG surgery. A new preoperative scoring system was devised to predict sternal SSI, which assigned 1 point for diabetes, 1 point for BMI of 30 or greater but less than 35, and 2 points for BMI of 35 or greater. Each point in the scoring system represented approximately a doubling of risk of SSI. The new scoring system performed better than the National Nosocomial Infections Surveillance System (NNIS) risk index at predicting SSI., Conclusion: A new weighted scoring system based on preoperative risk factors was created to predict sternal SSI risk following CABG surgery. The new scoring system outperformed the NNIS risk index. Future studies are needed to validate this scoring system.

Cases of gastroenteritis were examined to identify if dietary intake prior to an episode and food-handling and storage practices in the home were risk factors for illness. Cases and controls completed a dietary questionnaire after an event or when well, and questionnaires concerning food-handling, storage and general food-hygiene practices. Comparing cases to themselves when well. subjects were more likely to have eaten cold sliced salami, fried rice and foods cooked elsewhere, and to have had a baby in nappies in the house (OR 1.52-6.24, P< or =0.01). Cases compared to non-cases were more likely to have bought frozen poultry, have eaten foods cooked elsewhere and to have had a baby in nappies in the house (OR 1.44-2.05, P< or = 001). Although food-handling and storage practices are considered important, we were unable to detect an association in this study.