"Flurona": 5 minutes to understand the double infection of influenza and Covid-19

The news caused a sensation: In Israel, a pregnant woman was infected with two viruses at once: Covid-19 and influenza.

According to Israeli authorities, quoted by The Times of Israel, this woman was hospitalized in Tel Aviv and not vaccinated against these diseases.

She came out on Thursday in good health.

Quickly, the idea of ​​an alleged "merger", dubbed "Flurona", made the headlines.

In reality, it is rather a coexistence of two viruses.

Cases of double infection of Covid-19 and influenza were identified as early as 2020, in several countries.

A rare situation, say doctors, because viruses don't like being together.

This is also the reason why the arrival of a variant quickly supplants its predecessors.

Is co-infection dangerous?

"It's so unusual that we lack reliable data, we have no answer to this question," cautiously advances the infectious disease specialist Olivier Bouchaud, head of the infectious and tropical diseases department at the Avicenne hospital in Bobigny.

But since the symptoms are mostly the same, a sick person can carry both viruses without realizing it.

“In times of flu, we systematically carry out PCR tests for Covid and influenza, which is how we accidentally discovered patients carrying both viruses,” explains Olivier Bouchaud. If the case of the Israeli pregnant woman has been particularly publicized, it is therefore nothing new or extraordinary: several people in France, and elsewhere in the world such as in the United States and in China, have experienced this same double. infection. Sometimes developing classic mild symptoms.

A study from Bichat hospital, carried out during the first wave of Covid-19, shows that 6% of patients hospitalized for Covid were carriers of another infection (rhinovirus, flu, etc.).

"Co-infections can lead to viral interference, a virus limiting or suppressing the replication of the second virus, or to an increase in the severity of the disease compared to mono-infection", conclude the authors.

“These are two pathologies that will damage the lung tissue.

And your immune system will be overwhelmed, ”also warns infectious disease specialist Benjamin Davido.

What does this say about our immune system?

Here again, there are insufficient data on this subject to provide a formal answer.

But co-infections could develop more in people who have weaker immune systems.

"The case of the pregnant woman is not completely innocent, the immune system slows down to tolerate the fetus during pregnancy", notes Olivier Bouchaud.

At the start of Covid-19, scientists used the profile of the H1N1 flu to determine the risk factors: obesity, diabetes, hypertension, pregnant women.

“They turned out to be correct, the two viruses have the same preferential target,” recalls Benjamin Davido.

Does the Omicron variant promote double infection?

There is no reason to think so.

Co-infections existed before its onset.

The "downside" would be the high spread of Omicron: "If it causes many more cases than the others, mechanically, the probability of co-infection is greater", specifies Olivier Bouchaud.

Only barrier gestures and vaccination against influenza and Covid-19 can effectively curb this risk, the infectious disease specialists agree.

“The lockdowns have collapsed all the viruses.

And barrier gestures have given the flu and bronchiolitis a hard time, especially in 2020, ”continues Benjamin Davido.

Read also Barrier gestures, vaccination ... why the flu has disappeared this year

"Weariness, slackening in barrier measures reduces protection against all these respiratory viruses", analyzes virologist Bruno Lina, member of the scientific council, in Liberation.

If France is currently suffering the full brunt of the Omicron and Delta double wave, the peak of the flu often appears in early February.

Hence the importance of maintaining barrier gestures, even after this fifth peak in Covid cases.

“The question is, how long will the Omicron wave last?

asks Benjamin Davido.

Because if the Covid curve comes down soon, the flu could take over.

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