Flu Versus Cold: Battle Of The Respiratory Viruses

IRA FLATOW: And now it’s time to play Good Thing, Bad Thing–

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–because every story has a flip side, and you know it is time of the year for sniffles. Well, what exactly is the virus that’s making you sick? Researchers in Scotland took a survey of the viruses in the respiratory tract of thousands of patients to map out the viral ecology, the viral ecosystem, in those patient lungs.

And it turns out that if you have the flu, you are less likely to also be infected with the cold virus. Hmm. Joining me now to talk about this is Sema Nickbakhsh, a researcher in the MRC-University of Glasgow Centre for Virus Research in Glasgow, UK. Welcome to Science Friday, Dr. Nickbakhsh.

SEMA NICKBAKHSH: Hi, Ira. Thank you so much for the invitation to speak to you today.

IRA FLATOW: You’re very welcome. Fill us in on this. I think we all agree that getting the flu is bad news, especially if it’s bad enough to make you go see the doctor. But you found that there might be a hidden plus side to this.

SEMA NICKBAKHSH: Yeah. Well, our study is the first to try and provide robust quantitative evidence that there are interactions among flu viruses and non-flu viruses, including those that are responsible for the common cold, like you rightly said. And this hypothesis is something that’s not new news. It’s been around for decades, but we’ve not really had the robust quantitative evidence, and our study allowed us to really test that question.

IRA FLATOW: Do you have any idea why, if you have the flu virus, You don’t come down with the cold illness?

SEMA NICKBAKHSH: Yeah. Well, it’s a good question. So I’ll just start by explaining that, based on our data, we don’t actually know what the direction of the relationship is likely to be. But we do believe, based on the data that we have, that it is more likely that it’s the flu that blocks the common cold virus, rhinovirus, because we see it happen each year.

So each winter season, rhinovirus dips right at the time the flu virus peaks. And we even saw this during the summer wave of the 2009 flu pandemic, which is an unusual year for flu. There are others that have thought about the relationship the other way around based on that same pandemic period of flu. But our data is really suggesting that the relationship is likely to be the other way around.

And so these cold viruses, although they tend to be more mild in certain individuals and in the very young population, for example, or if you’re immunocompromised, then you can actually suffer from a more severe type of illness compared to, say, the average person.

IRA FLATOW: Could it be that if you have two viruses, they’re competing in your body for resources. And if you get the flu first, it sort of muscles out the cold virus?

SEMA NICKBAKHSH: Yeah. So those are the exact sorts of questions that we’re interested in because, you see, we– and by “we,” I mean biologists and epidemiologists– we tend to study pathogens as individual infectious organisms. But of course, the reality is that they co-circulate in the community together. And so it’s this ecological system that we’re wanting to understand better so that we can try to understand whether they are competing for host resources.

We also found in our analysis, which hasn’t been picked up on as much, is the fact that we see also cooperative forms of interaction among the cold viruses. But we don’t see this with flu viruses, and so there’s something different about flu. Whereas with the cold viruses, they can also have these more cooperative, rather than competitive, types of interactions is what our data is suggesting.

IRA FLATOW: Quite interesting. Thank you, Dr. Nickbakhsh for taking time to be with us today and have a happy holiday season to you.

SEMA NICKBAKHSH: No problem. Thank you. Happy Christmas. You too. Sema Nickbakhsh is a researcher in the MRC-University of Glasgow Centre for Virus Research in Glasgow, UK.