key: cord-0810443-qlu9m0vg authors: Sarvepalli, Siri S.; Cruz, Angela Beatriz V.; Chopra, Teena; Salimnia, Hossein; Chandrasekar, Pranatharthi title: Striking absence of “usual suspects” during the winter of the coronavirus disease 2019 (COVID-19) pandemic 2020–2021 date: 2021-06-24 journal: Infection control and hospital epidemiology DOI: 10.1017/ice.2021.303 sha: cb8a12e70d7c5a8e502dc2fdad2533029e7ead07 doc_id: 810443 cord_uid: qlu9m0vg nan including parainfluenza virus 1 and 2, other coronaviruses, and human metapneumovirus during the 2020-2021 season were also reviewed. During the study period in 2020-2021, no adult cases of influenza A, B, and RSV were documented, but these viruses comprised 12%, 13%, and 9% of all cases in the 2019-2020 season, respectively. Similarly, in children in 2020-2021, no influenza A or B infections and 1 RSV infection were documented, compared to 12%, 20%, and 24% of all cases, respectively, in 2019-2020 (Table 1) . Remarkably, there were also no positive tests due to parainfluenza (1 and 2), coronaviruses, and human metapneumovirus in the 2020-2021 season, a significant decline compared to the 2019-2020 season. Additionally, the number of throat swabs submitted for group A Streptococcus in both adults and children decreased considerably between the 2 periods. Overall, the incidence of influenza A and B and RSV in the 2020-2021 season affected by the COVID-19 pandemic decreased significantly compared to the 2019-2020 season in both the pediatric and adult populations. Additionally, the incidences of other respiratory viral infections (eg, parainfluenza 1 and 2), other coronaviruses, and human metapneumovirus were drastically lower. Additionally, data from 42 medical centers in the Midwest region of the United States that utilize the Biofire system respiratory viral panel were obtained and analyzed. 7, 8 In the same study period of September 2020-February 2021, there were far fewer positive tests of influenza A and B, RSV, parainfluenza, coronaviruses, and human metapneumovirus compared to the prior flu season. Among all flu tests in the 2020-2021 season, 0% of influenza A tests, 0.13% of influenza B tests, and 0.05% of RSV tests returned positive compared to 0.09%, 2.98%, and 9.38%, respectively, in the prior season. Human metapneumovirus had decreased to 0.05% positivity compared to 3.41% of all positive tests in the prior season. These data reflect a dramatic decrease in non-SARS-CoV-2 respiratory infections in the entire region. Speculating as to why the decrease in incidence of respiratory viral infections occurred, it is likely that community mitigating measures implemented at the beginning of the pandemic contributed to the decrease in the spread of viral pathogens in the general population. The reduction in group A Streptococcus tests ordered (and overall reduction in secondary group A Streptococcus infections) may have been a result of the decrease in the number of respiratory viral infections because clinical suspicion for secondary infections would have been low. Additionally, viral interference, with SARS-CoV-2 being the dominant respiratory pathogen, might have contributed to the decrease in rates of other respiratory viral illnesses. This idea is not unfounded. During the H1N1 pandemic in 2009, while the number of H1N1 influenza cases increased, the incidence of seasonal influenza and RSV decreased significantly compared to prior years. This trend lasted until the H1N1 strain transitioned from a pandemic to a seasonal virus the following year. 9 In conclusion, SARS-CoV-2 was the dominant pathogen, while other community respiratory viral and group A Streptococcus throat infections markedly declined in frequency in both adults and children during the 2020-2021 season compared to 2019-2020. The reason for the decline may be attributed to the mitigating measures widely employed in the community. Although it is difficult to predict the incidence of respiratory viral infections after the resolution of the COVID-19 pandemic, it is likely that the number of non-SARS-CoV-2 respiratory infections will rise back to normal in the coming years as SARS-CoV-2 becomes a seasonal virus. The flu season Respiratory syncytial virus burden among adults during flu season: an underestimated pathology Influenza vaccine effectiveness in the United States during the 2015-2016 season The impact of mask wearing and shelter in place on COVID-19 outbreaks in the United States How coronavirus lockdowns stopped flu in its tracks How COVID-19 is changing the cold and flu season Relationships between A(H1N1)pdm09 influenza infection and infections with other respiratory viruses Table 1. Proportion of Positive PCR Tests for SARS-CoV 2, Influenza A, Influenza B, RSV, and Group A Streptococcus Detroit Medical Center Total Tests (% Positivity) Pathogen Group A Streptococcus Note. PCR, polymerase chain reaction RSV, respiratory syncytial virus Acknowledgments.Financial support. No financial support was provided relevant to this article. All authors report no conflicts of interest relevant to this article.