Covid-19 and flu: why being infected with both viruses at the same time can be serious

It is possible to be infected with both Covid-19 and the flu. (© Illustration/Britany Colette/Unslpash)

Cough, fever aches… Between Covid-19 and the flu, the symptoms of these two respiratory viruses are often the same. And when the first is detected in the body, we do not necessarily dwell on the presence of the second.

However, you can be a carrier of both Covid-19 and the flu. That’s what we call a co-infection, and this is what worries the medical profession as respiratory viruses have been rampant in France in recent days. Explanations.

Double infected

Flurona is the name given to this double infection, a combination of “flu” for “flu” in English and “corona”. It was in December 2021 that researchers identified it with the case of a woman in Israel, who had contracted these two viruses at the same time. For its part, the World Health Organization (WHO) notes this double infection without recognizing “flurona” as a medical term.

A double infection which is not uncommon, as indicated by Jean-Daniel Lelièvre, immunologist and head of the infectious diseases department at Henri-Mondor hospital, interviewed by in January 2022:

It is absolutely not uncommon to be infected with two viruses at the same time. There are very many co-infected people, the antibodies are specific to a pathogen.

Jean-Daniel Lelievreimmunologist

And to cite the case of one of his patients infected simultaneously with HIV, the hepatitis C virus, that of hepatitis B, with cerebral toxoplasmosis and Covid-19, “ i.e. five infections concurrent actives.

Where the concern grows is that the contraction of these two respiratory viruses can prove to be even more dangerous.

No hybrid virus

These two viruses cannot mix in the body to become a kind of hybrid virus or a new sub-variant of Covid. What the WHO confirms: “If the influenza virus and SARS-CoV-2 (the virus responsible for Covid-19) infect a person simultaneously, this does not mean that a new disease has appeared.

What are the risks ?

Who says two viruses in the body, says more probability of developing a serious form explains Yves Buisson, epidemiologist and member of the Academy of Medicine:

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A double infection can increase the severity of cases and even mortality.

Yves Buissonepidemiologist

What a study in the scientific journal confirms The Lancet, released in March 2022, the largest to date. As part of the latter, 6,965 patients carrying Covid were tested and among them, 583 (8.4%) had a co-infection, including 227 for an influenza virus.

“Co-infection with influenza viruses was associated with an increased likelihood of receiving invasive mechanical ventilation (…) Co-infections were all significantly associated with increased increased risk of death“, can we read in this study.

Why it’s hard to identify

It is difficult to quantify the number of cases of co-infections. Apart from a study by Santé Publique France which highlighted, over the period from October 4, 2021 to May 17, 2022, 15 cases of influenza / Covid-19 co-infections, “but other cases remain under investigation. study”, nuances the epidemiologist.

Because “when we have Covid-19, we are not looking for other viruses”, points out Yves Buisson, especially since the symptoms are similar. In other words, it is possible that people who tested positive for Covid-19 were also carriers of the flu without knowing it.

What Professor Kenneth Baillie of the University of Edinburgh and author of the study by The Lancet “We should change our screening strategy at the hospital to also test a lot more for the flu virus. »

Call for vaccination

To limit or even avoid contamination, the health authorities keep repeating the usefulness of barrier gestures and the need for vaccination.

Especially since it is possible to be vaccinated at the same time against Covid-19 and the flu. It is even, since September 2021, a recommendation of the High Authority of Health:

This co-administration is a relevant solution for optimizing vaccination coverage against these two epidemics.

High Authority of Health

According to the Ministry of Prevention and Health, as of November 28, 2022, 337,000 concomitant injections (flu and Covid-19) were carried out compared to 284,000 last year over the same period.

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