Virologist: Experience from elsewhere suggests mild flu season ahead

Irja Lutsar.
Irja Lutsar. Source: Kairit Leibold / ERR

The flu season has begun early this year, with the number of cases rapidly rising. According to virologist Irja Lutsar, based on the experience of flu seasons in other parts of the world, nothing out of the ordinary ought to be expected in Estonia this winter. However, Lutsar said, the dangerous H3N2 flu virus is likely to spread more than in previous years.

According to the Estonian Health Board, the number of influenza cases is currently on the rise. While the spread of the flu virus is described as broad and persistent, the intensity of the illness is, according to the Health Board's assessment, average.

 Over the past week, the number of people with influenza in Estonia rose by 245 percent, while the number of hospitalizations related to the flu virus also increased by 60 percent.

According to Lutsar, data from Australia, which has already been through its own flu season, suggests that Estonia should expect a fairly typical, rather than exceptional, winter when it comes to the spread of the virus.

"It was milder than they (in Australia) expected, but it was a perfectly normal flu season. Which is similar to our current situation. They said that their (flu) season started very early, and we're also seeing that our flu season has started much earlier than usual," said Lutsar.

In general, what we see is that the emergence of seasonal viruses has become mixed up due to the pandemic. For example, the RS (respiratory syncytial) virus, which is mostly a spring-winter virus, has had outbreaks in summer during the pandemic," Lutsar said.

According to Lutsar, Australia has seen a large amount of the H3N2 influenza virus this season.

"It is the worst of the influenza viruses and can cause the most severe illnesses. Australia had a very severe flu season in 2017, and we had one 2018. However, mortality (rates) are now lower in Australia than in their 2017 season and fewer people were hospitalized.  If it holds true that we can make predictions (based on) Australia, then we can expect to see something similar (in Estonia)," she said.

In Australia, there had been fears ahead of the viral season of a potential double pandemic, with the flu and corona viruses both spreading rapidly at the same time. Fortunately, that did not happen. "The Australians themselves say, that one virus arrived first and then it started to decline. They didn't see the coexistence of Covid and flu," said Lutsar.

In Estonia too, influenza is currently the most dominant form of virus amongst the population, with the coronavirus only the fifth or sixth most prevalent.

According to Lutsar, after having spent the last couple of years isolating from the spread of viruses, societies are now repaying a form of "immunity debt."

"After all, there has been no flu really since April 2020. The fear was, that because our immune system is built in a way that it also needs to be stimulated, what other viruses are going to do, if they come back," said Lutsar.

"Some children, who would usually have contracted a cold in the first year or two of their lives, may not have had any illnesses yet. The fact that we were isolated from the viruses certainly plays a role, because our anti-viral antibodies need to be renewed. That hasn't happened for a couple of years. "Immunity debt" is a new term, which was coined during the pandemic, so we are now paying that back," said Lutsar.


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Editor: Michael Cole

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