Decline in Community Respiratory Viral Infections Observed During COVID-19 Pandemic

As COVID-19 cases skyrocketed in the United States throughout the pandemic, incidences of other respiratory viral infections dramatically declined.

Incidences of flu and respiratory syncytial virus (RSV) were dramatically reduced during the COVID-19 pandemic for both adult and pediatric populations compared with prior years, new research presented at the European Congress of Clinical Microbiology & Infectious Diseases showed.

The retrospective study compared the results of polymerase chain reaction tests of nasopharyngeal swabs for influenzas A and B, RSV, and SARS-CoV-2, and throat swabs for Group A streptococcus (GAS) conducted at Detroit Medical Center and Children’s Hospital of Michigan between September 2019-February 2020 and September 2020-February 2021. Researchers calculated the total incidence of infections to determine whether rates of respiratory infections fell during the COVID-19 pandemic.

For the adult population, in the 2019-2020 season, 11.5% of influenza A, 13.1% of influenza B, and 9% of RSV tests were positive. In the 2020-2021 season, 0% of influenza A, influenza B, and RSV tests were positive.

Data showed that 22.8% of GAS tests administered to adults in the 2019-2020 season were positive, whereas 23.11% were positive in the 2020-2021 season.

For the pediatric population, in the 2019-2020 season, 12.4% of influenza A, 20.2% of influenza B, and 23.7% of RSV tests were positive. In the 2020-2021 season, 0% of influenza A and influenza B were positive, and 1 RSV test was positive.

Positive results for GAS tests among the pediatric population showed a significant reduction, declining from 27.00% in the 2019-2020 season to 20.98% in the 2020-2021 season.

The trend of decline during the COVID-19 pandemic persisted for other, less common respiratory viruses. In 2019-2020, the positive rate of recovery ranged from 0.2% to 4.2% (coronavirus 229E: 0.2%; parainfluenza virus 2: 0.4%; parainfluenza virus 1: 3.5%; human metapneumovirus: 4.2%) compared with 0% in 2020-2021. There was also a dramatic reduction in the amount of GAS tests ordered in the 2020-2021 season vs previous years.

Community mitigating measures implemented in response to the COVID-19 pandemic, such as social distancing, school closures, and masks may have contributed to the decrease in the spread of viral pathogens. A decline in respiratory viral infections may have subsequently contributed to the decline in positive tests for GAS, as GAS typically follows viral upper respiratory tract infections. Viral interference involving COVID-19, the dominant pathogen at the time of data analysis, may have blocked co-infection from other viruses and contributed to the decline in rates of other respiratory viral illnesses.

Despite the recent decline in cases of flu and other respiratory infections, “it is likely that incidences will return to normal in the coming years as SARS-CoV-2 becomes a seasonal virus,” concluded lead study author Siri Sarvepalli, an MD candidate at Wayne State University School of Medicine. During a typical flu season, in the United States, 9 to 45 million cases of influenza virus infections occur in all age groups, and other respiratory infections such as RSV and rhinovirus are common.


Sarvepalli SS, Cruz ABV, Chopra T, Salimnia H, Chandrasekar P. Striking absence of “usual suspects” during the winter of the COVID-19 pandemic. Presented at: European Congress of Clinical Microbiology & Infectious Diseases; July 9-12, 2021. Abstract 02678. Accessed July 9, 2021.