What are the main issues concerning the next flu season?

#TogetherAgainstFlu - 29/04/21

An interview with Dr Richard Webby from the Infectious Disease Department at St. Jude Children’s Research Hospital

  • There are low numbers of flu viruses currently circulating but this does not mean the virus has gone away.
  • While COVID-19 is currently the main concern, this will change once current pandemic restrictions loosen.
  • Influenza is going to come back because now population-level immunity is lower.
  • To bring population immunity back up, it is important to get vaccinated against flu.

With concerns over low influenza awareness and increased exposure to influenza viruses, Dr Richard Webby talks about changes he sees ahead, why he believes the flu is coming back and, what the population should be doing now.

Dr Richard Webby is also the Director of the World Health Organization Collaborating Center for Studies on the Ecology of Influenza in Animals. He has a basic research program, funded by ALSAC, the fundraising arm of St Jude, and the US National Institutes of Health, that focuses on influenza viruses at the human-animal interface. This work involves virologic and serologic surveillance activities in animal and human populations to determine the prevalence of influenza viruses present.

Thinking ahead, what do you see as the main issues of low circulating flu viruses?

Richard: I think it’s important to note, although we do have low numbers of flu viruses circulating, they are still circulating. Even in countries that are reporting very low activity, there is still the flu virus there. It hasn’t gone away. It just hasn’t reached the level for meeting the definition of an epidemic.

We have had some countries in parts of Africa and parts of Southeast Asia that have had reasonable amounts of flu activity this season. So, again, it hasn’t gone away; some countries are still having to deal with flu.

In terms of what’s going to happen with regards to the flu season in the southern hemisphere and northern hemisphere, I think there is a big question mark. I would imagine, at least by the time the next northern hemisphere flu season rolls around, the amount of SARS-CoV-2 virus that’s circulating is going to be reduced.

I think with the loosening of social distancing and mask-wearing, that it’s going to open the door for flu to come right back in. So, I think we will experience flu like we normally do but we need to now ask; is the flu going to come back worse? We haven’t had much flu circulation for a good season and a half. It is a question we don’t have a good answer to right now.

Why could less circulation of the flu virus lead to it coming back even worse, could you explain what this means? I know at one point, my colleague mentioned that the immunisation of the population lowers; could you explain this process?

Richard: Every year, during a flu season, anywhere between 5%, 10%, even up to 30% of people in a population can get infected with the virus. So, when they get infected with the virus, that boosts their immune response and boosts their immunity to the virus. Come next season though, some of that boosted immunity may still be around.

What we have now in the northern hemisphere are potentially flu seasons with very low activity, we haven’t had that boosting or that immunity in that 10% 20% 30% of the population. So, what we call the population immunity to flu may be a little bit lower than usual.

People are getting vaccinated as well, but what percentage of the population is that?

Richard: Of course, it varies from country to country. So, I think there is the possibility that population-level immunity will be lower, and I think that does drive home the point that vaccinations are one way to bring population immunity back up.

Why is flu still important this year and why should we not overlook it during this COVID-19 pandemic? What should the population still be doing?

Richard: I think we have to look back at history, certainly over the last century. This flu virus has come every winter to temperate regions and caused a lot of hospitalisations and deaths. Globally hundreds of thousands of hospitalisations and deaths every year because of flu, and with the potential exception of this year, that’s every year we have had flu.

If we look back at what’s happened with coronavirus, we’ve had other animal coronavirus jump over from other animal species into humans but then they settle into the season. I think that’s probably where the SARS-CoV-2 virus is headed as well. But once we start to get population immunity to that virus, either through infection or vaccination, I do see that it will settle down into a cold-like disease pattern. So again, I think looking at history; coronavirus can come over, cause a lot of problems for a while, but then settle down.

However, the flu doesn’t do that. It is continually causing problems year after year. So, for me, there’s no evidence to suggest that it’s not going to progress as well. Right now, COVID-19 is the pathogen of our immediate concern, but I think that’s almost certainly going to change with the flu coming back.

I understand that there may be a potential new high-risk group emerging after the COVID infection called long COVID (i.e., people who been very heavily impacted by COVID). Will this be a group risk, do you think?

Richard: It’s an interesting question as it’s currently unknown. So, we do have people who are having continuing problems after the acute COVID-19 phases, I think it’s a bit early to say about these people, but it’s absolutely possible.

So, what would be a good message that we should be passing on?

Richard: The message is that the flu hasn’t gone. Activity is very low, but the flu has not gone, and it will come back. Without a doubt, influenza is going to come back. And again, I think by far the best thing we can do is to prepare ourselves to be vaccinated.

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