Influenza A virus can aggravate COVID-19 infection in cell and animal tests, according to a study published in the journal Cell Research by Chinese researchers.

Some experts have warned that the seasonal flu merging with the current COVID-19 pandemic may pose a larger threat to public health. However, the interaction between influenza viruses and the novel coronavirus remained unclear.

The study by Chinese researchers from Wuhan University in central China's Hubei Province provides strong experimental evidence concerning the coinfection of the two respiratory viruses. It reported for the first time that influenza A virus can enhance subsequent COVID-19 infection in cells and mice.

Researchers found that the existing infection of influenza A virus significantly promoted the entry and replication of the novel coronavirus in a variety of human respiratory tract cells and lung tissue cells, while it also elevated the COVID-19 viral load, leading to more severe lung damage in coinfected mice.

In further experiments, similar promotive effects on COVID-19 infection were not observed with several other respiratory viruses, indicating that influenza A virus has a unique ability to aggravate COVID-19 infection, and thus, the prevention of influenza infection is of great significance during the COVID-19 pandemic, said the study.

Researchers recommended both influenza vaccination and COVID-19 vaccination to people with a high risk of coinfection. They also emphasized that the development of novel broad-spectrum antiviral drugs targeting more than one virus is necessary for the treatment of coinfectious diseases.