Heat can reduce the spread - but not stop the infection

When the corona virus began to spread throughout the world, it was also hoped that it could be a so-called "seasonal virus", which spreads worse during the summer months.

That hope remains.

"If you look at other airway viruses, it usually does," says Anders Wallensten, assistant state epidemiologist at the Public Health Authority.

The reason why this virus would also be seasonally dependent is, among other things, the comparison with previous coronaviruses.

- When you reach an average temperature of up to five to ten degrees, when spring arrives, the number of corona drops begins to disappear. With covid-19, there is no reason to think, scientifically, that it would behave differently in terms of heat, says Nicklas Sundell, infectious physician and virus researcher at Sahlgrenska University.

He recently defended his thesis on viruses in the upper respiratory tract and has studied, among other things, how four other types of coronavirus are affected by heat.

Like the other four corona virus, sars-cov-2 has a protective grease.

- Grease envelope virus is more sensitive to environmental factors. This means that the fat casing quickly dries out when it gets hot, he says.

Now there are also a number of preliminary studies on the new corona virus that indicate that the spread of infection may be slower in warmer weather. Among other things, a study from Hubei Province in China.

- But it is difficult to distinguish it from restrictions that have been made, such as people staying at home and reducing their travel, which surely had a much stronger effect, says Anna-Mia Ekström, professor of global infection epidemiology at KI.

But the experts disagree. Former state epidemiologist Johan Giesecke does not believe heat affects the survival of the virus at all.

- I don't believe in that. I don't think the virus infects less in the summer, but it is about changing our contact pattern in the summer, he says.

The fact that we are more outdoors in the summer, and for example going to a summer place and meeting less people, makes the virus spread worse during the hot months, he says.