Coinfection with Influenza A, SARS-CoV-2 May Suppress COVID-19 Severity, According to Study

For coinfected patients who first contract influenza A, replication of SARS-CoV-2 may be suppressed, even 1 week after clearance of influenza A.

Coinfected patients who contract influenza A virus before SARS-CoV-2 may experience a suppressed severity of SARS-CoV-2, according to a study recently published in the Journal of Virology.

The study found that coinfection of SARS-CoV-2 and influenza A virus does not change the trajectory or the severity of Influenza A virus, regardless of timing. However, coinfected patients who contract Influenza A virus first may find that the response to that infection can significantly suppress SARS-CoV-2.

“The research is important, because the human population now has 2 circulating respiratory RNA viruses with high pandemic potential: SARS-CoV-2 and influenza A,” wrote the researchers. “As both viruses infect the airways and can result in significant morbidity and mortality, it is imperative that we also understand the consequences of coinfection.”

Several studies have reported on the coinfection of SARS-CoV-2 with other viruses, as well.

“In particular, coinfection with SARS-CoV-2 and influenza A virus was common early in the COVID-19 pandemic, prior to the enforcement of masks and social distancing,” corresponding author Benjamin R. tenOever, PhD, a professor of microbiology at New York University, Langone Health, said in a press release.

The researchers performed experiments in cultured cells and a golden hamster animal model in which the animals were administered the 2 viruses simultaneously and examined periodically after infection.

Additional experiments were conducted in which the animals were first challenged with 1 virus, followed by the other virus 3 days later. These animals were observed at days 1, 3, and 5 after the second virus was administered.

The researchers found that influenza A virus interferes with SARS-CoV-2 replication in the lung. According to their findings, the interference can even continue more than 1 week after clearance of influenza A.

"These data suggest the presence of factors intrinsic to or induced by [influenza A virus] that may restrict the growth of SARS-CoV-2, but it remains unclear whether this effect plays a role on disease severity," the researchers wrote.

However, tenOever suggests that “this study could be used as an example of how an immune response to something unrelated can provide protection against SARS-CoV-2."

The results also demonstrated that coinfection does not result in a worse outcome of disease in an animal model. "These results suggest that coinfection with SARS-CoV-2 and influenza A virus does not represent a looming threat for humanity," tenOever concluded.


Coinfection with influenza A could suppress replication in SARS-CoV-2, study shows. Science Daily website. Published July 12, 2022. Accessed July 13, 2022.

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