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Peer-to-peer (P2P) and multicast approaches are two common transmission strategies to provide scalable and cost efficient solutions for video-on-demand (VoD) services. The former approach requires small server resources and provides a negligible delay to users, but the bandwidth requirement inside the network will be rapidly increased when more customers join the video session. On the other hand, if the system simply uses a multicast scheme to deliver a video, customers will experience a noticeable delay before watching the video whereas the overall bandwidth requirement will not be significantly increased. In this paper, a new transmission policy denoted peer-to-peer batching (PPB) policy is proposed to efficiently deliver video data in a large scale VoD system by exploiting the multicast capability of the network and P2P paradigm. To avoid the disruption of services, the fault tolerance and recovery mechanism is also developed for PPB. In addition, in order to further improve the scalability of the system, a distributed PPB (DPPP) is also proposed. We then develop a mathematical model to evaluate the performance of each of our proposed policies analytically. Based on this model, system designers are able to study various design options as well as perform system dimensioning. Both analytical and simulation results show that the proposed scheme achieves better system performance compared with existing schemes. Index Terms--Fault exception, multicast, peer-to-peer (P2P), reliability, video-on-demand (VoD).

Abstract Background The objective of this study is to estimate the incidence of genital warts in Hong Kong and explore a way to establish a surveillance system for genital warts among the Hong Kong general population. Methods A total of 170 private doctors and all doctors working in the 5 local Social Hygiene Clinics (SHC) participated in this study. During the 14-day data collection period (January 5 through18, 2009), the participating doctors filled out a log-form on a daily basis to record the number of patients with genital warts. The total number of new cases of genital warts presented to private and public doctors in Hong Kong was projected using the stratification sampling method. Results A total of 721 (0.94%) adults presented with genital warts to the participating doctors during the two-week study period, amongst them 73 (10.1%) were new cases. The projected number of new cases of genital warts among Hong Kong adults was 442 (297 male and 144 female) during the study period. The incidence of genital warts in Hong Kong was estimated to be 203.7 per 100,000 person-years (respectively 292.2 and 124.9 per 100,000 person-years for males and females). Conclusions The incidence of genital warts is high among adults in Hong Kong. The study demonstrates the importance of collecting surveillance data from both private and public sectors.

Abstract Background The incidence and prevalence of sexually transmitted infection (STI) in China has been on the rise in the past decade. Delineation of epidemiologic pattern is often hampered by its uneven distribution. Spatial distribution is often a neglected aspect of STI research, the description of which may enhance epidemiologic surveillance and inform service development. Methods Over a one month-period, all first time attendees of 6 public STI clinics in Hong Kong were interviewed before clinical consultation using a standard questionnaire to assess their demographic, clinical and behavioural characteristics. A GIS (geographic information system)-based approach was adopted with mapping performed. The cases attending the clinics in different locations were profiled. A comparison was made between neighbourhood cases (patients living near a clinic) and distant cases (those farther off), by calculating the odds ratio for demographic, behavioural and geographic characteristics. Results Of the 1142 STI patients evaluated, the residence locations of 1029 (90.1%) could be geocoded, of which 95.6% were ethnic Chinese and 63.4% male. Geographically only about a quarter lived in the same district as the clinic. STI patients aged 55 or above were more likely to be living in the vicinity of the clinic, located in the same or adjacent tertiary planning unit (a small geographic unit below district level). A majority of patients came from locations a few kilometers from the clinic, the distance of which varies between clinics. Overall, more syphilis cases were reported in patients residing in the same or adjacent tertiary planning unit, while distant cases tended to give a higher risk of inconsistent condom use. There were otherwise no significant clinical and epidemiologic differences between neighbourhood and distant STI cases. Conclusions There was no specific relationship between STI and the residence location of patients as regards their clinical and epidemiologic characteristics in the territory of Hong Kong. Older STI patients were however more inclined to attend the nearby STI clinics. Most patients have travelled a variable distance to access the STI service. The relationship between STI clinic cases and distance could be a complex issue intertwined between psychosocial characteristics and STI service coverage.

Neurosyphilis is a difficult clinical stage of syphilis as there is no ideal method for diagnosis and workup requires lumbar puncture which may sometimes provide ambiguous results especially in HIV co-infected patients. Enzyme immunoassay is a widely used screening test for syphilis in serum, but its test performance was not well studied in cerebrospinal fluid. To examine the diagnostic performance of cerebrospinal fluid-enzyme immunoassay (CSF-EIA) in neurosyphilis, we conducted a prospective study for two years. All consecutive patients admitted for workup of neurosyphilis under the Social Hygiene Service, in Hong Kong, were included. Laboratory tests on CSF included several serological tests, CSF cell count, and protein. Forty-five patients were prospectively recruited, of which 29 people were living with HIV / AIDS. Using diagnostic case definition standard stipulated in the IUSTI 2008 guidelines, 17 patients satisfied the diagnosis of neurosyphilis. The CSF-EIA test provided 100% in both sensitivity and negative predictive value; its specificity was 46.4% (13/28, 95% CI 31.8–61%). Specificity improved to 80.8% (95% CI: 68.4–93.2%) with optical density cut-off value at 1.4 for cases with CSF red cell counts <600/mm3. This is the first study on use of CSF-EIA in neurosyphilis. CSF-EIA showed high sensitivity and high negative predictive value in the study population and the presence of CSF red cells < 600/mm3 might not affect its accuracy. [ABSTRACT FROM PUBLISHER]

• Mycoplasma genitalium was detected in 8% of patients with non-gonococcal urethritis. • M. genitalium infection commonly occurred alone or in association with Chlamydia trachomatis infection. • Macrolide- and/or fluoroquinolone-resistance-associated mutations were common. • The M. genitalium resistance pattern varied within the Asia Pacific region and between continents. Mycoplasma genitalium is the cause of an emerging sexually transmitted infection (STI) with high propensity for development of antimicrobial resistance. In a prevalence study conducted at the public STI service in Hong Kong, the first void urine samples of 38 (8%) of 493 male patients with non-gonococcal urethritis (NGU) tested positive for M. genitalium using reverse transcription polymerase chain reaction. Patients with M. genitalium infection were younger [31 vs 33 years, odds ratio (OR) 0.96, 95% confidence interval (CI) 0.93–0.996; P =0.03], more likely to present with urethral discharge (12% vs 6%, OR 2.16, 95% CI 1.10–4.23; P =0.02) and had symptom duration >2 weeks (14% vs 6%, OR 2.34, 95% CI 1.10–4.97; P =0.03) compared with patients without M. genitalium infection. The prevalence of M. genitalium infection was lower in patients co-infected with Chlamydia trachomatis compared with patients with isolated infection (4% vs 10%, OR 0.38, 95% CI 0.17–0.84; P =0.02). The prevalence of M. genitalium infection was not higher in men who have sex with men. Antimicrobial-resistance-conferring mutations were present in 24 (63%) patients with M. genitalium – 23S rRNA 18 (47%) and parC 19 (53%). Similar to neighbouring countries in the Asia Pacific region, concurrent resistance mutations against both macrolides and fluoroquinolones were demonstrated in 14 (37%) patients. Histories of azithromycin and moxifloxacin use were significantly associated with a diagnosis of M. genitalium infection. Characteristically, NGU in Hong Kong featured the co-existence of mono-resistance against macrolides or fluoroquinolones, and the presence of dual class resistance. The geographic variability of antimicrobial resistance against M. genitalium is attributed not just to the different transmission networks formed in separate population groups, but the antimicrobial prescriptions for the treatment of urethritis in the community. [ABSTRACT FROM AUTHOR]

Background: Chlamydia causes infertility and increases risk of HIV infection, and population-based studies provide essential information for effective infection control and prevention. This study examined Chlamydia trachomatis prevalence and risk factors among a representative sample of 18-49-year-old residents in Hong Kong., Methods: Census boundary map of 412 constituency areas was used as primary sampling units to construct the sampling frame and, residential buildings and units were randomly selected using geospatial modelling. A questionnaire on sexual practice and health was conducted, and polymerase chain reaction was used to test the urine for genital chlamydial infection. Invitation letters were sent to the selected households and a team of interviewers were sent to recruit one subject per household. Prevalence data was weighted according to the 2011 census and risk factors identified through logistic regression., Results: Among 881 participants (response rate of 24.5%), the overall Chlamydia trachomatis prevalence was low at 1.4% (95%CI 0.8-2.5%) but sexually active young (18-26 years) women had relatively high prevalence (5.8%, 95%CI 1.7-18.2%) in Hong Kong. A unique U-shape disease burden was observed with peaks in younger and older (40-49 years) women. Amongst the sexually active women, the risk factors of Chlamydia trachomatis infection were: younger age (aOR = 25.4, 95% CI 2.81-230); living alone (aOR = 8.99, 95% CI 1.46-55.40); and, among all the sexually active participants, males (including the male partners of the female participants) who had travelled out of Hong Kong in the previous 12 months had higher risks of infection (aOR = 5.35; 95% CI 1.25-22.8). A core-peripheral geographical distribution of Chlamydia trachomatis prevalence was also observed., Conclusion: Young and older sexually active women in Hong Kong have high prevalence of chlamydia. Routine screening for sexually active women and young men should be considered. Further research on testing feasibility and linkage-to-care are urgently needed to control the infection.

Co-infection of human immunodeficiency virus (HIV) and neurosyphilis (NS) has become a rising trend, but the extent of brain damage associated with the concomitant infections remains unknown. Proton magnetic resonance spectroscopy ((1)H-MRS) can evaluate metabolic changes underlying early brain infections. 25 syphilitic patients (7 HIV-positive with NS; 6 HIV-positive without NS; 5 HIV-negative with NS; 7 non-HIV, non-NS) and 17 healthy controls (HC) underwent single-voxel (1)H-MRS in the bilateral hippocampi. Absolute concentrations of major metabolites were measured using a 3T MRI scanner. No significant structural abnormality was detected in all patients. However, metabolic changes were found in the left hippocampus of both the HIV-positive and NS subgroups, showing significantly higher choline (Cho), creatine (Cr) and myo-inositol (mI) compared to HC. In the right hippocampus, HIV-positive subgroup showed significantly higher Cr and reduced NAA, while NS subgroup only showed significantly reduced NAA compared to HC. The non-HIV, non-NS syphilitic subgroup showed no significant difference compared to HC. Substantial metabolic changes occurred in bilateral hippocampi in HIV and NS co-infections. NAA reduction might represent early neuronal damage, while mI/Cho elevation reflects gliosis/inflammatory changes. (1)H-MRS could serve as a non-invasive tool to triage patients suspected of NS for lumbar puncture in non-HIV syphilitic patients.