Levels of influenza and other non-COVID-19 respiratory viruses were at historic lows for most of 2020, according to a new report from the Centers for Disease Control and Prevention. There is still very little circulating flu, but other viruses (including parainfluenza viruses and common human coronaviruses, which cause colds), have a resurgence out of season in 2021.
Between October 2020 and May 2021, flu levels in the United States were the lowest since 1997, the first year that flu season data are available, according to the analysis. Very little flu has been reported worldwide and experts believe that the protective measures taken by people against COVID-19 (masking, distancing) suppressed the virus.
This year’s nearly non-existent flu season could mean the fall and winter flu season could be more severe, the CDC report warned. Because there was not much flu around, people may not be exposed to the virus at the same rates as they normally would. This could reduce normal levels of immunity to the virus. “Lower levels of immunity in the population, especially among younger children, could portend more widespread disease and a potentially more serious epidemic when the circulation of the flu virus is resumed,” the report’s authors wrote. . That means it will be especially important for doctors and nurses to encourage anyone over the age of six months to receive the flu vaccine this fall, they said.
Circulation of respiratory syncytial virus (RSV), a virus that causes colds in adults but can be dangerous for infants, was also silenced during 2020 and early 2021. Rates began to rise again in the April 2021, which is usually unusual levels of this virus peak in January. Parainfluenza viruses and common human coronaviruses followed a similar trend: levels were low until 2020 and then began to rise in February 2021.
The public health measures used to curb the spread of COVID-19 likely helped suppress these viruses during 2020 and they recovered again when U.S. communities began lifting some of these restrictions. It is not yet clear exactly how the flu and various cold-causing viruses respond to the different strategies used against COVID-19, so trends in these viruses could be unpredictable over the next year as efforts to continue. fight the pandemic.
“Clinicians need to be aware that respiratory viruses may not exhibit typical seasonal circulation patterns and that a resumption of circulation of certain respiratory viruses is occurring,” the CDC report said.
The increase in cold-causing viruses can also make it difficult to tell the difference between the symptoms of COVID-19 and the symptoms of other diseases for people and their doctors. During 2020, any cold or flu-like symptoms are likely to be COVID-19 – it was one of the only viruses around. Now that other viruses are back, the picture could be more bleak.