Co-circulation of respiratory viruses during the SARS-CoV-2 Alpha surge

By Dr. Priyom Bose, Ph.D.Jun 16 2022Reviewed by Emily Henderson, B.Sc.

Scientists and policymakers have devised many strategies to reduce the emergence and spread of the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the causal agent of the ongoing coronavirus disease 2019 pandemic (COVID-19). For example, people have been urged to practice physical distance, wear face masks, wash their hands frequently, and dine close to each other indoors. 

Brief Report: Reduction and persistence of co-circulating respiratory viruses during the SARS-CoV-2 pandemic. Image Credit: Corona Borealis Studio/ Shutterstock

Background

The implementation of various measures formulated to prevent the spread of the SARS-CoV-2 virus has also contributed significantly to the reduction in influenza cases. According to the Centers for Disease Control and Prevention (CDC), only 0.2% of specimens tested positive for influenza between September 28, 2020, and May 22, 2021. However, this was not the case in the previous three influenza seasons, where the number of positive cases ranged between 26.2 and 30.3%.

Reduced influenza cases indicate the effectiveness of mitigation measures taken to limit SARS-CoV-2. Yet it remains unclear whether the control measures would be effective against other respiratory viruses as well.

A New Study

Recently, scientists evaluated the influence of mitigation measures that were originally implemented to restrict COVID-19 transmission, on other respiratory viruses. This study is available as pre-proof in AJIC: American Journal of Infection Control.

In this study, researchers studied a molecular respiratory pathogen panel on nasopharyngeal (NP) swabs obtained from symptomatic patients who opted for drive-through COVID-19 testing centers at the University of North Carolina Hospital’s Respiratory Diagnostic Center (RDC) between January 15 and April 15, 2021. The authors considered all samples that were negative for SARS-CoV-2. 

Researchers used a molecular respiratory pathogen panel, approved by the US Food and Drug Administration (FDA), to screen various respiratory pathogens including endemic coronaviruses (HKU1, NL63, 229E, OC43), adenovirus, rhinovirus/enterovirus, parainfluenza virus (PIV) 1, PIV2, PIV3, PIV4, metapneumovirus, influenza A (A/H1, A/H3, A/H1-2009), influenza B, respiratory syncytial virus (RSV), Chlamydia pneumoniae, Bordetella pertussis, Bordetella parapertussis, and Mycoplasma pneumoniae. 

Key Findings

According to this study, 8.5% of 5,068 symptomatic outpatients were infected with SARS-CoV-2. The rest of the samples were available for additional testing by the molecular respiratory panel. Researchers revealed that the SARS-CoV-2 Alpha variant was circulating as the dominant strain during the study period.

Scientists reported that 18% of the samples available for the molecular respiratory panel, exhibited infection by rhinovirus/enterovirus. Other viruses detected were RSV, PIV 2, PIV 3, metapneumovirus, adenovirus, and endemic coronaviruses (229E, NL63, OC43). Interestingly, researchers observed that bacterial targets and influenza viruses were not detected in any of the tested samples.

The current study strongly suggested that infection by some respiratory viruses, such as influenza, could be prevented via the implementation of prevention measures (e.g., changes in social behavior). 

Study Implications

The authors stated that the reduction in the transmission of influenza viruses has occurred due to multiple factors, and one of the key factors has been the implementation of mitigation strategies to inhibit SARS-CoV-2 transmission. The presence of other viruses, such as rhinovirus/enterovirus, indicates that their mode of transmission differs from SARS-CoV-2. 

During the COVID-19 pandemic, scientists and policymakers have particularly focussed on formulating mitigation measures based on preventing the spread of respiratory aerosols and droplets generated by SARS-CoV-2 infected patients. There was less attention paid to the possibility of virus transmission via contaminated surfaces.

Previous studies have indicated that enveloped viruses (e.g., SARS-CoV-2 and influenza) are easily inactivated by frequent hand washing and use of disinfectants, while non-enveloped viruses (e.g., rhinovirus/enterovirus) could not be managed via these measures. 

This study strongly suggests that nonpharmaceutical prevention measures have significantly lowered the spread of the majority of respiratory viruses compared to previous seasons. However, the increased use of surface disinfectants, especially in hospitals and nursing homes, has been strongly recommended.