Covid and flu, the explosive cocktail that awaits us this winter

Although Covid infections are currently at low or declining levels in most Western countries (with the exception of the UK) there is still a long way to go before the threat of a pandemic is definitely over. One of the big concerns this winter is to know if there will be, again, a strong resurgence of the Covid … and if other respiratory diseases will come back in force at the same time -notably influenza.

Both in the southern hemisphere and in the northern hemisphere, influenza infections last winter were rapidly diminished and largely disappeared shortly after the pandemic. The physical distancing measures used to curb the spread of the Covid have been even more effective in containing the flu.

Unfortunately, that means we need to prepare for the flu to be particularly bad this year.

In a way, the immune responses to Covid and the flu are similar. A relatively recent infection or vaccination offers a good protection against subsequent infection, but which tends to wear off quickly. Early re-infections are usually asymptomatic or relatively mild. But the longer the delay between the acquisition of immunity and reinfection, the greater the subsequent infection. risk of being serious.

This is especially clear when looking at how the flu affects people who live on remote islands. As they can go long periods without being exposed to this pathogen, when they do eventually contract it, their mortality rate are higher. A study involving people living in Tristan da Cunha, a group of isolated islands in the South Atlantic, found that having a few years between two flu exposures seemed to increase the risks.

We are less well armed than usual in the face of the flu

In a way, we have all lived on remote islands since the start of 2020 due to successive confinements, travel restrictions and working at home … It is therefore to be feared that the Covid control measures having severely limited public exposure to influenza over the past eighteen months, natural immunity has fallen across the population.

When the flu returns, it could affect more people and cause more serious illness than in a normal season. It will probably be the same for other respiratory viruses. In fact, it may already be the case: recently there have been numerous reports of particularly severe colds UK.

However, it is not easy to predict when exactly the flu will come back, or how much more severe or more frequent it will be. Currently, influenza rates are still quite low in the UK [comme en France, ndlr], but that could change quickly if the virus starts to spread.

Fortunately, we have safe and effective influenza vaccines that reduce both the risk of infection and serious illness. But they are not as effective that most current Covid vaccines. In addition, their effectiveness varies from year to year. As influenza viruses mutate faster, several strains eventually circulate and they change every year. If the dominant winter virus strain was not included when the vaccine was designed, its effectiveness will be lower.

In addition to being potentially more susceptible to the flu ourselves, there is a higher risk of having a less effective vaccine.

Recommendations for which versions of the virus to include in annual influenza vaccines – created separately for northern and southern hemisphere winters – are made by theWorld Health Organization, which assesses strains that have circulated previously.

A specificity of the looming winter: the cases of influenza having been few in the last eighteen months, it was more difficult than usual to predict which strains would be dominant this winter. So in addition to being potentially more susceptible to the flu ourselves due to weaker immune defenses, there is also a higher risk of having a less effective vaccine.

How it all combines with the Covid

Even before the pandemic, winter flu exerted significant pressure on people every year. general medicine services and the hospitals in England [comme en France, ndlr]. Managing it at a time when the health service is already welcoming many Covid patients would be particularly difficult and would intensify the pressure on the health service.

There is an additional risk: co-infection. It is possible to contract Covid at the same time as another infection – bacterial, fungal or viral. In fact, a study who looked at patients hospitalized for a Covid estimated that 19% of them were also carriers of another infection. And it was found that co-infected patients were more likely to die.

At the start of the pandemic, while the flu was still circulating, British scientists were able to compare results of people with Covid alone and Covid-flu co-infection. People with co-infection were about twice as likely to be admitted to intensive care, require ventilation and die than those who only had Covid.

It is not possible to say if we will see a major flu epidemic this year … Even if we do not this time around, it is almost certain that it will happen in the near future. When the flu returns, it is likely to affect more people than in most pre-Covid years and cause more deaths – but how much? In a bad winter, the flu kills more than 20,000 people in England [en France, 2 à 8 millions de personnes sont habituellement touchées avec un excès de mortalité de 10.000 à 15.000 décès, ndlr].

Because of the direct threat it poses – and the increased pressure that the flu will place on health services that are likely to still struggle to cope with Covid – it is doubly important that the public accept the offer of flu shots and Covid booster shots if and when offered to them this fall.

This article is republished from The Conversation under a Creative Commons license. Read thearticle original.


Source: Slate.fr by www.slate.fr.

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