Abstract
A well 6-month-old infant with coronavirus disease 2019 (COVID-19) had persistently positive nasopharyngeal swabs up to day 16 of admission. This case highlights the difficulties in ...establishing the true incidence of COVID-19, as asymptomatic individuals can excrete the virus. These patients may play important roles in human-to-human transmission in the community.
Highly effective vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been developed but variants of concerns are worrisome, especially B.1.617.2 (Delta) which has ...rapidly spread across the world. We aim to study if vaccination alters virological and serological kinetics in breakthrough infections.
We conducted a multicentre retrospective cohort study of patients in Singapore who had received a licensed mRNA vaccine and been admitted to hospital with B.1.617.2 SARS-CoV-2 infection. We compared clinical features, virological and serological kinetics (anti-nucleocapsid, anti-spike and surrogate virus neutralization titres) between fully vaccinated and unvaccinated individuals.
Out of 218 individuals with B.1.617.2 infection, 84 received an mRNA vaccine of which 71 were fully vaccinated, 130 were unvaccinated and four received a non-mRNA vaccine. Despite significantly older age in the vaccine breakthrough group, only 2.8% (2/71) developed severe COVID-19 requiring oxygen supplementation compared with 53.1% (69/130) in the unvaccinated group (p < 0.001). Odds of severe COVID-19 following vaccination were significantly lower (adjusted odds ratio 0.07 95% CI 0.015–0.335, p 0.001). PCR cycle threshold values were similar between vaccinated and unvaccinated groups at diagnosis, but viral loads decreased faster in vaccinated individuals. Early, robust boosting of anti-spike protein antibodies was observed in vaccinated patients; however, these titres were significantly lower against B.1.617.2 than the wildtype vaccine strain.
The mRNA vaccines are highly effective at preventing symptomatic and severe COVID-19 associated with B.1.617.2 infection. Vaccination is associated with faster decline in viral RNA load and a robust serological response. Vaccination remains a key strategy for control of the COVID-19 pandemic.
Imported Monkeypox, Singapore Yong, Sarah Ee Fang; Ng, Oon Tek; Ho, Zheng Jie Marc ...
Emerging infectious diseases,
08/2020, Letnik:
26, Številka:
8
Journal Article
Recenzirano
Odprti dostop
In May 2019, we investigated monkeypox in a traveler from Nigeria to Singapore. The public health response included rapid identification of contacts, use of quarantine, and postexposure smallpox ...vaccination. No secondary cases were identified. Countries should develop surveillance systems to detect emerging infectious diseases globally.
Understanding the circumstances that lead to pandemics is important for their prevention. We analyzed the genomic diversity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) early in ...the coronavirus disease 2019 (COVID-19) pandemic. We show that SARS-CoV-2 genomic diversity before February 2020 likely comprised only two distinct viral lineages, denoted "A" and "B." Phylodynamic rooting methods, coupled with epidemic simulations, reveal that these lineages were the result of at least two separate cross-species transmission events into humans. The first zoonotic transmission likely involved lineage B viruses around 18 November 2019 (23 October to 8 December), and the separate introduction of lineage A likely occurred within weeks of this event. These findings indicate that it is unlikely that SARS-CoV-2 circulated widely in humans before November 2019 and define the narrow window between when SARS-CoV-2 first jumped into humans and when the first cases of COVID-19 were reported. As with other coronaviruses, SARS-CoV-2 emergence likely resulted from multiple zoonotic events.
Surveillance and reporting of epidemiological features of seasonal influenza mostly are aggregates across all‐ages. We investigated age‐specific differences in distribution of influenza virus ...(sub)types in tropical Singapore, using laboratory‐confirmed virological data collected under the national influenza surveillance programme from 2011 to 2017. The proportion of influenza‐positive specimens from outpatients with influenza‐like illness was used as an indicator of influenza activity in the community. The highest influenza positivity for age groups of 5 to 14 years and 15 to 64 years coincided in the same month in 5 out of the 7 years under study. Influenza positivity was lowest in young children <5 years of age compared with older age groups. Influenza A(H3N2) was most prevalent in the community except in 2012 when a predominance of influenza B was observed. The dominant virus (sub)type varied across the years in children <5 years and 5 to 14 years of age. Influenza A(H3N2) was the predominant circulating virus subtype among elderly persons aged ≥65 years during the 7‐year period, and among adults aged 15 to 64 years since 2013. Knowledge about the age‐specific differences in distribution of influenza virus (sub)types helps to facilitate better understanding of seasonal epidemics and to inform targeted strategies in prevention and control of influenza virus transmission.
Highlight
Influenza peak for age groups of 5–14 years and 15–64 years mostly coincided in the same month.
Influenza positivity was lowest in young children <5 years of age.
Children <5 years of age experienced a mixture of influenza A and B viruses as the predominant types.
Age groups of 5–14 years and 15–64 years were mostly affected by A(H3N2) followed by influenza B.
Influenza A(H3N2) was particularly prevalent in elderly persons aged ≥65 years.
Background
Respiratory syncytial virus (RSV) is an important respiratory pathogen that affects people of all ages.
Objectives
We examined the patterns of RSV circulation in 2014‐2018, and ...investigated their age‐specific differences in tropical Singapore.
Methods
Nasopharyngeal and/or throat swabs were taken from outpatient attendees for the national influenza virological surveillance among those who presented with acute respiratory illness in the community. Specimens tested negative for influenza were then tested for RSV and other respiratory pathogens.
Results
Among 8436 influenza‐negative specimens tested during the five‐year period, 5.8% (95% confidence interval 5.3%‐6.3%) were positive for RSV. The peak of RSV activity occurred around middle of the year. The age‐specific proportion of RSV detections showed a reverse J‐shaped pattern; RSV positivity was the highest in young children ≤2 years of age (10.9%), followed by those aged 3‐5 years (6.4%) and persons aged ≥65 years (5.3%), while the nadir was observed in the age group of 15‐24 years (1.2%). RSV type A was predominantly circulating in children ≤5 years of age from 2014 to 2015 and 2017, whereas in 2016, they were more affected by type B.
Conclusion
Respiratory syncytial virus was more frequently detected among the two age groups that have been recommended for influenza vaccination; persons ≥65 years of age and children 6 months to <5 years of age. Characterisation of RSV activity in the community helps to better inform public health policies for effective prevention and control interventions.
Early diagnosis is crucial in securing optimal outcomes in the HIV care cascade. Recent HIV infection (RHI) serves as an indicator of early detection in the course of HIV infection. Surveillance of ...RHI is important in uncovering at-risk groups in which HIV transmission is ongoing. The study objectives are to estimate the proportion of RHI among persons newly-diagnosed in 2013-2017, and to elucidate epidemiological factors associated with RHI in Singapore.
As part of the National HIV Molecular Surveillance Programme, residual plasma samples of treatment-naïve HIV-1 positive individuals were tested using the biotinylated peptide-capture enzyme immunoassay with a cutoff of normalized optical density ≤ 0.8 for evidence of RHI. A recent infection testing algorithm was applied for the classification of RHI. We identified risk factors associated with RHI using logistic regression analyses.
A total of 701 newly-diagnosed HIV-infected persons were included in the study. The median age at HIV diagnosis was 38 years (interquartile range, 28-51). The majority were men (94.2%), and sexual route was the predominant mode of HIV transmission (98.3%). Overall, 133/701 (19.0, 95% confidence interval CI 16.2-22.0%) were classified as RHI. The proportions of RHI in 2015 (31.1%) and 2017 (31.0%) were significantly higher than in 2014 (11.2%). A significantly higher proportion of men having sex with men (23.4, 95% CI 19.6-27.6%) had RHI compared with heterosexual men (11.1, 95% CI 7.6-15.9%). Independent factors associated with RHI were: age 15-24 years (adjusted odds ratio aOR 4.18, 95% CI 1.69-10.31) compared with ≥55 years; HIV diagnosis in 2015 (aOR 2.36, 95% CI 1.25-4.46) and 2017 (aOR 2.52, 95% CI 1.32-4.80) compared with 2013-2014; detection via voluntary testing (aOR 1.91, 95% CI 1.07-3.43) compared with medical care; and self-reported history of HIV test(s) prior to diagnosis (aOR 1.72, 95% CI 1.06-2.81).
Although there appears to be an increasing trend towards early diagnosis, persons with RHI remain a minority in Singapore. The strong associations observed between modifiable behaviors (voluntary testing and HIV testing history) and RHI highlight the importance of increasing the accessibility to HIV testing for at-risk groups.
MOP (Multidrug/Oligosaccharidyl-lipid/Polysaccharide) family transporters are found in almost all life forms. They are responsible for transporting lipid-linked precursors across the cell membrane to ...support the synthesis of various glycoconjugates. While significant progress has been made in elucidating their transport mechanism, how these transporters select their substrates remains unclear. Here, we systematically tested the MOP transporters in the Streptococcus pneumoniae capsule pathway for their ability to translocate noncognate capsule precursors. Sequence similarity cannot predict whether these transporters are interchangeable. We showed that subtle changes in the central aqueous cavity of the transporter are sufficient to accommodate a different cargo. These changes can occur naturally, suggesting a potential mechanism of expanding substrate selectivity. A directed evolution experiment was performed to identify gain-of-function variants that translocate a noncognate cargo. Coupled with a high-throughput mutagenesis and sequencing (Mut-seq) experiment, residues that are functionally important for the capsule transporter were revealed. Lastly, we showed that the expression of a flippase that can transport unfinished precursors resulted in an increased susceptibility to bacitracin and mild cell shape defects, which may be a driving force to maintain transporter specificity.
All licensed pneumococcal vaccines target the capsular polysaccharide (CPS). This layer is highly variable and is important for virulence in many bacterial pathogens. Most of the CPSs are produced by the Wzx/Wzy mechanism. In this pathway, CPS repeating units are synthesized in the cytoplasm, which must be flipped across the cytoplasmic membrane before polymerization. This step is mediated by the widely conserved MOP (Multidrug/Oligosaccharidyl-lipid/Polysaccharide) family transporters. Here, we systematically evaluated the interchangeability of these transporters and identified the residues important for substrate specificity and function. Understanding how CPS is synthesized will inform glycoengineering, vaccine development, and antimicrobial discovery.
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