“We thought SARS-CoV-2 would follow the same pattern as influenza, with a clear winter peak. But the virus has been present more or less all year round,” [says Gunnveig Grødeland, a professor of immunology at the University of Oslo and head of the Centre for Pandemics and One-Health Research (P1H).]
According to the Norwegian Institute of Public Health (NIPH), test results show an increase in Covid-19 cases in Norway after the summer holidays.
That the virus still circulates year-round is surprising to researchers.
For a virus to keep spreading year-round, it needs to find people still vulnerable to infection – those who haven’t developed neutralising antibodies.
A possible explanation could have been that the coronavirus mutates faster than other viruses.
But that’s not the case, according to Grødeland.
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“In fact, influenza, which has a strong seasonal pattern, changes far more rapidly than SARS-CoV-2,” she says.
The size of future infection waves depends on how susceptible the population is, and how long immunity lasts after vaccination or infection.
The virus’ ability to mutate and produce new variants is also a factor.
