Broad decline and subsequent differential re-emergence of respiratory viruses during COVID-19 pandemic response measures, Singapore 2020 (preprint)

ImportanceCOVID-19 pandemic control measures affect the prevalence of other respiratory viruses. Effects on some viruses have been described; however, the broader impact and temporal relationship of control measures on virus decline and subsequent re-emergence have not been thoroughly documented. Understanding these phenomena may influence health policies. ObjectiveTo examine the prevalence of unrelated respiratory viruses in relation to population-wide pandemic response measures and phases in 2020 in Singapore. Design, Setting, and ParticipantsData from respiratory multiplex PCRs from 3 major hospitals (total 3700 beds) in Singapore were collated. The full dataset consisted of 42,558 test results, 19,898 from 2019 and 22,660 from 2020. Main Outcomes and MeasuresWeekly virus prevalence data were mapped onto prevailing pandemic response measures, in order to elucidate temporal relationships and differential virus responses. Pre-pandemic data from 2019 were compared with data from 2020. ResultsEarly response measures, even before national lockdown, were followed by a dramatic reduction of influenza viruses and a more gradual decline of other respiratory viruses, including respiratory syncytial virus, parainfluenza viruses, endemic coronaviruses and metapneumovirus. Marked decline of enterovirus/rhinovirus and adenovirus, however, was only observed during lockdown. About 13 weeks into phased reopening, enterovirus/rhinovirus re-emerged, followed by adenovirus, the latter mainly in the pediatric population. All other viruses remained at low levels until the end of 2020. Conclusions and RelevanceCOVID-19 control measures in Singapore had a significant impact on a broad range of respiratory viruses. Effects of various control measures varied between phases and different viruses. Influenza viruses declined earliest and most dramatically; relaxation of measures was followed by re-emergence of enterovirus/rhinovirus and adenovirus. These patterns are presumably a result of different propensities for contact versus droplet and overall ease of transmission, and different virus reservoirs. Further studies into these phenomena are a matter of public health importance. Key PointsO_ST_ABSQuestionC_ST_ABSWhat were the effects of COVID-19 pandemic control measures in Singapore on the prevalence of other respiratory viruses? FindingsViruses responded differently to control measures. Influenza viruses declined rapidly after early control measures and remained near-absent during reopening after lockdown. Enterovirus/rhinovirus and adenovirus declined later and re-emerged earlier than other viruses during phased reopening. MeaningPopulation-wide interventions resulted in a broad decline and subsequent differential re-emergence of non-targeted respiratory viruses, corresponding to different patterns of virus response to control measures.

SARS-CoV-2 Viral RNA Load Dynamics in the Nasopharynx of Infected Children (preprint)

It is important to understand the temporal trend of pediatric severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral load to estimate the transmission potential of children in schools and communities. We determined differences in SARS-CoV-2 viral load dynamics between nasopharyngeal samples of infected asymptomatic and symptomatic children. The daily cycle threshold values of SARS-CoV-2 in the nasopharynx of a cohort of infected children were collected for analysis. Among 17 infected children, 10 (58.8%) were symptomatic. Symptomatic children, when compared to asymptomatic children, had higher viral load (mean cycle threshold on day 7 of illness 28.6 versus 36.7, p = 0.02). Peak SARS-CoV-2 viral loads occured around days 2-3 of illness/days of diagnosis in infected children. After adjusting for the estimated date of infection, the higher SARS-CoV-2 viral loads in symptomatic children remained. We postulate that symptomatic SARS-CoV-2-infected children may have higher transmissibility than asymptomatic children. As peak viral load in infected children occurred in the early stage of illness, viral shedding and transmission in the pre-symptomatic phase probable. Our study highlights the importance of screening for SARS-CoV-2 in children with epidemiological risk factors, even when they are asymptomatic in order to improve containment of the virus in the community, including educational settings. Key pointsO_LISymptomatic children had higher SARS-CoV-2 viral loads in the nasopharynx than asymptomatic children, which may indicate that symptomatic children have higher transmissibility. C_LIO_LIPeak SARS-CoV-2 viral loads occurred early around 2-3 days post symptom onset iin children and therefore, pre-symptomatic transmission of the virus is probable. C_LIO_LISymptom based screening for SARS-CoV-2 may not be effective in diagnosing coronavirus disease 2019 (COVID-19) in children as a proportion of children may be asymptomatic or pauci-symptomatic. C_LIO_LIChildren with high epidemiological risk factors should be screened or isolated as they may be carriers of the virus and contribute to transmission. C_LI