Global analysis suggests that COVID-19 is seasonal

Urbana, Illinois-Is it possible that seasonality is partly due to the re-blockade of cities around the world as the number of COVID-19 surges? A new study from the University of Illinois says so.

In a treatise published in Evolutionary bioinformaticsResearchers in Illinois have shown that COVID-19 cases and mortality are significantly correlated with temperature and latitude in 221 countries, among other epidemiological indicators.

“One conclusion is that the disease can be seasonal, like the flu, which we expect from now on after the vaccine controls these first waves of COVID-19. It has a lot to do with what we should do, “said Professor Gustavo Caetano Anores of the department. He is a professor and lead author of the paper at Crop Sciences, an affiliate of the Carl R. Wars Institute for Genome Biology, Illinois.

The seasonality of viral illnesses is so widespread that it has become part of the English language. For example, we often talk about the “flu season” to show the high incidence of influenza during the cold winter months. Early in the pandemic, researchers and public health officials suggested that SARS-CoV-2 could behave like other coronaviruses. Many raise their heads in the fall and winter. However, there was a shortage of data, especially on a global scale. The work of Caetano-Anollés and his students bridges that particular knowledge gap.

First, researchers downloaded relevant epidemiological data (morbidity, mortality, recovery, activity, testing rates, hospitalization) from 221 countries, along with latitude, longitude, and mean temperature. They got the data from April 15, 2020. This is because the date represents the moment of a particular year when seasonal temperature fluctuations are greatest in the world. The date also coincided with the early pandemic period when COVID-19 infections peaked everywhere.

The research team then used statistical methods to test whether epidemiological variables correlate with temperature, latitude, and longitude. In warmer countries near the equator, the effects of the disease were expected to be minimal.

“Certainly, our global epidemiological analysis showed a statistically significant correlation between temperature and incidence, mortality, recovery and activity. As expected, the same trend at latitudes. It was seen, but not in longitude, “says Caetano-Anollés.

Temperature and latitude were undoubtedly correlated with COVID-19 cases, but researchers quickly pointed out that climate is the only factor driving seasonal COVID-19 outbreaks worldwide.

They explained other factors by standardizing live epidemiological data to per capita morbidity and assigning each country a risk indicator that reflects public health preparedness and the incidence of comorbidities in the population. In countries with scarce resources and countries with higher than average rates of diabetes, obesity and old age, the risk indicators were considered more important than temperature in the analysis. But it wasn’t. The index did not correlate with the disease index at all.

In an early study by Caetano-Anollés and his colleagues, regions of the SARS-CoV-2 viral genome mutated rapidly, some were found in new viral variants in the United Kingdom, and others were more stable. It was confirmed that there was. Similar viruses show seasonal increases in mutation rates, so the researchers looked for a relationship between changes in viral mutations and the temperature, latitude, and longitude of sites whose genomes were sampled worldwide. ..

“Our results suggest that the virus is changing at its own pace and that mutations are affected by factors other than temperature and latitude. What these factors are exactly. I don’t know, but it can be said that seasonal effects are independent of the genetic makeup of the virus, “says Caetano-Anollés.

Caetano-Anollés states that more research is needed to explain the role of climate and seasonality in the incidence of COVID-19, but the impact of policies such as mask obligations, and others. Cultural factors such as expectations for paying attention to people are also key players. However, he does not underestimate the importance of understanding seasonality when fighting viruses.

Researchers say our own immune system may be partly involved in seasonal patterns. For example, the immune response to influenza can be affected by body temperature and nutritional status, such as vitamin D, which plays an important role in immune defense. We do not get enough of that vitamin due to our low exposure to sunlight during the winter. But for COVID-19, it’s too early to say how seasonality and the immune system interact.

“We know that influenza is seasonal and we take a break during the summer, which gives us the opportunity to make an influenza vaccine next fall,” says Caetano-Anollés. “When we’re still in the midst of a raging pandemic, that break doesn’t exist. Perhaps learning how to boost the immune system is struggling to keep up with the ever-changing coronavirus. May help fight illness. “