In a study published recently in the journal Evolutionary Bioinformatics, Illinois researchers said COVID-19 cases and mortality rates showed a strong correlation with temperature and latitude across 221 countries.
The research suggests that the virus that causes COVID-19 (SARS-CoV-2) could behave similarly to many other coronaviruses, which tend to circulate more widely during the fall and winter.
That hypothesis was introduced by researchers and public health officials early in the pandemic, but it didn’t have a significant amount of data to back it up at the time. Now, researchers have had enough time to analyze global data and conclude that the disease may turn out to become seasonal.
"One conclusion is that the disease may be seasonal, like the flu. This is very relevant to what we should expect from now on after the vaccine controls these first waves of COVID-19," said lead author Gustavo Caetano-Anollés, a professor at the C.R. Woese Institute for Genomic Biology at the University of Illinois at Urbana-Champaign.
The research team that carried out the study said the SARS-CoV-2 virus genome appears to be mutating in a way that has connections to climate and seasons.
"Our results suggest the virus is changing at its own pace, and mutations are affected by factors other than temperature or latitude. We don't know exactly what those factors are, but we can now say seasonal effects are independent of the genetic makeup of the virus," Caetano-Anollés said in a statement.
More research needed
The researchers added that further research is needed before it can be concluded that COVID-19 rates will ebb and flow with the seasons. The team said that people’s immune systems -- which are affected by temperature and nutrition -- could also influence COVID-19 trends. In the winter months, people tend to fall short in getting enough vitamin D, the authors said.
"We know the flu is seasonal and that we get a break during the summer. That gives us a chance to build the flu vaccine for the following fall," Caetano-Anollés said. "When we are still in the midst of a raging pandemic, that break is nonexistent. Perhaps learning how to boost our immune system could help combat the disease as we struggle to catch up with the ever-changing coronavirus."