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

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

Scientists and policymakers have developed many strategies to reduce the emergence and spread of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the causative agent of the current coronavirus disease pandemic. 2019 (COVID-19). For example, people have been asked to practice physical distancing, wear face masks, wash their hands frequently and dine next 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


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

The reduction in influenza cases indicates the effectiveness of the mitigation measures taken to limit SARS-CoV-2. Yet it remains unclear whether the control measures would also be effective against other respiratory viruses.

A new study

Recently, scientists assessed the influence of the mitigation measures initially implemented to limit transmission of covid-19, on other respiratory viruses. This study is available as pre-proof in AJIC: American Journal of Infection Control.

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

Researchers used a US Food and Drug Administration (FDA)-approved Molecular Respiratory Pathogen Panel to screen for various respiratory pathogens, including endemic coronavirus (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.

Main 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 further testing by the Molecular Respiratory Panel. The researchers revealed that the SARS-CoV-2 Alpha variant was circulating as the dominant strain during the study period.

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

The current study strongly suggests that infection with certain respiratory viruses, such as influenza, could be prevented by implementing preventive measures (eg, social behavior changes).

Implications of the study

The authors stated that the reduction in influenza virus transmission occurred due to several factors, and one of the key factors was the implementation of mitigation strategies to inhibit the transmission of SARS- CoV-2. 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 been particularly focused on formulating mitigation measures based on preventing the spread of respiratory aerosols and droplets generated by patients infected with SARS-CoV-2 . Less attention has been paid to the possibility of transmission of the virus via contaminated surfaces.

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

This study strongly suggests that non-pharmaceutical prevention measures have significantly reduced 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, was strongly recommended.

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