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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.
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<p><b>INTRODUCTION</b>Singapore was one of 29 countries worldwide affected by severe acute respiratory syndrome (SARS) in 2003.</p><p><b>MATERIALS AND METHODS</b>There were 238 cases identified during the outbreak. We performed a retrospective analysis of the clinical and laboratory data of 234 patients admitted to Tan Tock Seng Hospital and Singapore General Hospital.</p><p><b>RESULTS</b>The mean age of patients was 21 years, 31.6% of patients were males and 41.8% were healthcare workers. At presentation, the common symptoms were fever, myalgia, cough and headache; rhinorrhoea was uncommon. On admission, 21% had leukopenia, 18% had thrombocytopaenia, 29% had hyponatraemia, 31% had hypokalaemia, 21% had transaminitis. Polymerase chain reaction (PCR) testing of respiratory and stool samples provided the best yield at the end of the first week of illness. Thirty-two patients were initially not recognised as probable SARS and were reclassified when the serology test results were available. The chief reasons for not identifying these patients early were persistently normal chest X-rays (68.8%), very mild presentation (43.8%) and the presence of a concomitant illness (12.5%). Overall, 12% of the patients were probable SARS with atypical presentations. Overall mortality was 11.8%.</p><p><b>CONCLUSION</b>Patients infected with the SARS coronavirus had a wide clinical presentation with non-specific symptoms.</p>
