Transmission modes of severe acute respiratory syndrome coronavirus 2 and implications for infection control: a review

The complete picture regarding transmission modes of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is unknown. This review summarises the available evidence on its transmission modes, our preliminary research findings and implications for infection control policy, and outlines future research directions. Environmental contamination has been reported in hospital settings occupied by infected patients, and is higher in the first week of illness. Transmission via environmental surfaces or fomites is likely, but decontamination protocols are effective in minimising this risk. The extent of airborne transmission is also unclear. While several studies have detected SARS-CoV-2 ribonucleic acid in air samples, none has isolated viable virus in culture. Transmission likely lies on a spectrum between droplet and airborne transmission, depending on the patient, disease and environmental factors. Singapore's current personal protective equipment and isolation protocols are sufficient to manage this risk.

Risk factors and time-trends of cytomegalovirus (CMV), syphilis, toxoplasmosis and viral hepatitis infection and seroprevalence in human immunodeficiency virus (HIV) infected patients

<p><b>INTRODUCTION</b>Chronic bacterial, viral and parasitic infections contribute to the morbidity and mortality associated with human immunodeficiency virus (HIV) infection. This study investigated risk factors and time-trends of the seroprevalence of cytomegalovirus (CMV), toxoplasmosis and hepatitis A total antibody; and co-infection with syphilis, hepatitis B and hepatitis C among newly diagnosed HIV individuals in Singapore.</p><p><b>MATERIALS AND METHODS</b>This was a cross-sectional study. A random sample of 50% of HIV infected patients who visited the Communicable Disease Centre (CDC), Singapore for first-time care from January 2006 to December 2011 were analysed.</p><p><b>RESULTS</b>Among the 793 study subjects, 93.4% were male; 77.9% of them were of Chinese ethnicity; mean age at HIV diagnosis was 41.4 years; and the mean baseline CD4+ T-cell count was 222 cells/mm³. The prevalence of sero-reactivity for CMV was 96.8%; hepatitis A: 40.9%; and toxoplasmosis: 23.7%. Co-infection with syphilis was identified in 12.3%; hepatitis B: 8.1%; and hepatitis C: 2%. Among those co-infected with hepatitis C, 73.3% of them were intravenous drug user (IVDU). Syphilis co-infection was significantly more common among men who have sex with men (MSM) (multivariate OR: 2.53, 95% CI, 1.31 to 4.90, P = 0.006).</p><p><b>CONCLUSION</b>This study described the baseline rates of HIV co-infection with syphilis, hepatitis B and C in Singapore, and sero-reactivity to CMV, toxoplasmosis and hepatitis A. The increased rates compared to the general population may have important consequences for disease progression, response to antiretroviral treatment and long-term general health.</p>

Challenges of respondent driven sampling to assess sexual behaviour and estimate the prevalence of human immunodeficiency virus (HIV) and syphilis in men who have sex with men (MSM) in Singapore

There is a lack of representative samples to provide reliable and accurate seroprevalence of sexually transmitted infections (STIs) and human immunodeficiency virus (HIV) as well as behavioural information among men who have sex with men (MSM) in Singapore. We used respondent driven sampling (RDS) to recruit MSM. Participants completed a survey used by Asian Internet MSM Sex Survey (AIMSS) and were tested for HIV and syphilis. We compared the characteristics of the RDS participants with STI diagnosis against those who did not have any STI diagnosis in the past 6 months. We compared RDS participants with AIMSS participants. Of 72 MSM recruited, 1 was positive for HIV (1.3%) and 4 (5.5%) tested positive for syphilis. Median age was 30 years and majority was Chinese (69.4%). RDS participants who had any STI diagnosis reported to have more use of recreational drugs (P = 0.006), and lower condom use (P = 0.054). Comparing RDS participants (n = 72) with the AIMSS participants (n = 2075), RDS respondents had ≥1 male partner in the past 6 months (P = 0.003), more casual sex partners (P = 0.012) and more STI symptoms (P = 0.019). There was no difference in terms of HIV testing and recreational drug use. The HIV and syphilis seroprevalence rates from our study are similar to previous reports conducted in high-risk MSM. In contrast to other settings, RDS did not work well among MSM in Singapore. The public health implications of our study highlight the challenges in obtaining data for HIV surveillance in assessing prevalence and risk behaviours among MSM.

Clinical evaluation of an in-house human immunodeficiency virus (HIV) genotyping assay for the detection of drug resistance mutations in HIV-1 infected patients in Singapore

<p><b>INTRODUCTION</b>Human immunodeficiency virus type 1 (HIV-1) genotyping resistance test (GRT) is essential for monitoring HIV-1 drug resistance mutations (DRMs). High cost and HIV-1 genetic variability are challenges to assay availability in Singapore. An in-house Sanger sequencing-based GRT method was developed at the Communicable Disease Centre (CDC), Singapore's HIV national treatment reference centre for both subtype B and non-subtype B HIV-1.</p><p><b>MATERIALS AND METHODS</b>The in-house GRT sequenced the fi rst 99 codons of protease (PR) and 244 codons of reverse transcriptase (RT) in the pol gene. The results were compared with the Food and Drug Administration (FDA)-approved ViroSeq™ HIV-1 Genotyping System.</p><p><b>RESULTS</b>Subtype assignment for the 46 samples were as follows: 31 (67.4%) CRF01_AE, 14 (30.5%) subtype B and 1 (2.1%) subtype C. All 46 samples had viral load of ≥500 copies/mL, and were successfully amplified by the in-house primer sets. Compared to the ViroSeq™ test, our in-house assay showed drug-resistance conferring codon concordance of 99.9% at PR and 98.9% at RT, and partial concordance of 0.1% at PR and 1.1% at RT. No discordant result was observed.</p><p><b>CONCLUSION</b>The assay successfully identified DRMs in both subtype AE and B, making it suitable for the efficient treatment monitoring in genetically diverse population. At less than half of the running cost compared to the ViroSeq™ assay, the broadly sensitive in-house assay could serve as a useful addition to the currently limited HIV genotyping assay options for resource-limited settings, thereby enhancing the DRM surveillance and monitoring in the region.</p>

Causes of death in hospitalised HIV-infected patients at a National Referral Centre in Singapore: a retrospective review from 2008 to 2010

<p><b>INTRODUCTION</b>Highly active antiretroviral therapy (HAART) has improved outcomes for individuals infected with human immunodeficiency virus (HIV). This study describes the causes of death in hospitalised HIV-positive patients from 2008 to 2010 in Tan Tock Seng Hospital, the national referral centre for HIV management in Singapore.</p><p><b>MATERIALS AND METHODS</b>Data were retrospectively collected from HIV-positive patients who died in Tan Tock Seng Hospital from January 2008 to December 2010.</p><p><b>RESULTS</b>Sixty-seven deaths occurred in the study period. A majority of patients died of non-acquired immune deficiency syndrome (AIDS)-defining illnesses (54.7%). The median CD4 count was 39.5 (range, 20.0 to 97.0), and 7 patients had HIV viral loads of <200 copies/mL. There were 27 deaths due to opportunistic infections, 27 due to non AIDS-defining infections, 4 due to non AIDS-associated malignancies. This study also describes 3 deaths due to cardiovascular events, and 1 due to hepatic failure. Patients who had virologic suppression were more likely to die from non AIDS-defining causes.</p><p><b>CONCLUSION</b>Causes of death in HIV-positive patients have changed in the HAART era. More research is required to further understand and address barriers to testing and treatment to further improve outcomes in HIV/AIDS.</p>

Older age at initial presentation to human immunodeficiency virus (HIV) care and treatment at the Communicable Disease Centre (CDC) in Singapore, 2006 to 2011

<p><b>INTRODUCTION</b>The incidence of newly diagnosed older patients diagnosed with human immunodeficiency virus (HIV) has increased worldwide in recent years. In this study, we compared the demographics and clinical presentation of younger and older patients in our HIV sentinel cohort.</p><p><b>MATERIALS AND METHODS</b>Among all HIV patients presenting to the Communicable Disease Centre (CDC), Singapore from 2006 to 2011, 793 were randomly included in our cohort, representing about 50% of the patients seen during that period. We collected demographic, clinical, laboratory, and outcome data from patient records to compare younger (<50 years old) and older (≥50 years old) HIV patients.</p><p><b>RESULTS</b>Older patients comprised 27.1% of our HIV cohort and presented with lower median CD4 T cell counts (65 cells/mm³, interquartile range [IQR]: 27 to 214 cells/mm³) compared to younger patients (250 cells/mm³, IQR: 74 to 400 cells/mm³; P <0.001). The median time from HIV diagnosis to initiation of antiretroviral therapy (ART) differed significantly for both age groups as well (49 days for patients <50 years old, IQR: 18 to 294 days; versus 35 days for patients ≥50 years old, IQR: 14 to 102 days; P = 0.008). More of our younger patients were single (72.2%) or homosexual (44.1%), in contrast to older patients, of whom 48.8% were married and 84.7% were heterosexual.</p><p><b>CONCLUSION</b>Upon comparison of our younger and older patients, we identified distinct differences in risk transmission and clinical presentation. Increased awareness of older patients at risk of HIV may improve time to diagnosis among this age group.</p>