Health: What a pandemic means for the immune system – Wikipedia

Weak defenses? Many diseases such as influenza and whooping cough have become rare in this epidemic. Photo: Susan Brauch/dpa


Some diseases are becoming rarer in the Corona pandemic. But recently, some people have had the impression that they are getting sick at an unusual rate. Are the body’s defenses out of practice?

Berlin – Not again: every few weeks children get sick – colds, gastrointestinal, etc. Some adults also report the impression that they take every cold with them at the moment.

After two years of countless calls for action to avoid infection and with travel restrictions, the many requirements of the home office, masks, coughs and sniffs may seem unusual. Especially at this time of year. But is there more to her? Have our immune systems forgotten how to defend themselves against pathogens due to lack of activity?

Remarkably unusual developments

Many diseases such as influenza and whooping cough are becoming rare in the epidemic, says Bernd Salzberger, president of the German Society for Infectious Diseases, of the University Hospital Regensburg. At the beginning of 2021, an analysis by the Robert Koch Institute (RKI) of several notifiable diseases from tuberculosis to hepatitis E showed that between March and the beginning of August 2020, a third fewer cases were reported than expected based on the previous year’s values ​​- Covid-19 excluded. Respiratory diseases, for example, have fallen particularly sharply, which is also the result of corona measures such as masks and distance.

But what is the situation now, when droplets and aerosols and thus many pathogens can often pass between people again unimpeded? If you look at data from the RKI’s Influenza Working Group, which, in addition to influenza and Covid-19, deals with common cold pathogens such as rhinoviruses, unusual developments can be observed.

Flu viruses, for example, have only been on the rise among children since Easter – the time when the season usually comes to an end. After the flu pandemic failed two seasons ago, the 2021/202 numbers still indicate very restrictive events overall.



The curve of the estimated rate of respiratory diseases as a whole in the population reflects this to some extent: since January it has been much higher than the 2021/201 season, which was severely affected by Corona, but did not reach the heights of the three. The pre-pandemic seasons, during which the influenza pandemic prevailed. Instead, things now seem to lag longer in the spring: over the past few weeks, the RKI has shown higher values ​​than at this time in the previous four seasons.

However, general practitioners do not see a situation completely out of the ordinary. “We do not currently observe any significant accumulation of respiratory diseases in general practices,” a spokesperson for the German Association of General Practitioners said. “The situation can vary from region to region, so that general practitioners there treat a particularly large number of patients with similar symptoms.” However, no clear trend can be identified at the national level.

‘The immune system is not a muscle’

But what is the truth of the prevailing suspicion that immune systems have been weakened by the epidemic or corona measures? “The immune system is not a muscle: it does not decline when it is not used or used less,” says Karsten Watzel, general secretary of the German Society of Immunology. Sure, the immune system has survived a bit over the past couple of years, but it hasn’t become redundant. “However, there was something that had to be done: People come into contact with pathogens not only through the respiratory system, but also through the skin or food, so that the immune system kicks in.”

An immunologist has a different interpretation: for some colds, you simply have to do it every two or three years. “Seasonal coronaviruses are a case in point. Anyone who has lost them in the past two years can now catch several colds in a row. This is a compensatory effect, similar to what was seen with RSV infection in children last fall.” RSV stands for respiratory syncytial virus. It can cause severe pneumonia and is especially dangerous for premature babies, infants, and young children. There was also a big wave among children in other countries.

Experts also see – as a result of the epidemic – increased interest in the topic and possibly a change in self-perception as a result. “During a pandemic, many of us are used to not having colds for a long time at a time,” Watzl says. “And even before that, it was always the case that we were affected.”

Increasingly common pathogens from the animal kingdom

Watzl says the unusual outbreak of monkeypox currently observed cannot be explained by immune systems in Western countries supposedly weakened by the epidemic. “It’s the case where pathogens from the animal kingdom spread to humans more frequently.” This is due to the fact that people are increasingly infiltrating previously undeveloped areas – and the numerous international travel movements. “We’ll see such diseases more frequently in the future,” Watzel says. “If you think about the emergence of MERS, SARS, and SARS-CoV-2, monkeypox is fairly harmless.”

From the scientists’ point of view, he advises caution next fall: “If we don’t deal with influenza in these years, chances are the virus will ‘run away’ from us in evolution, so we’ll eventually deal with a virus we don’t know very well,” says Salzberger. But the immune system does not forget old confrontations so quickly.

Antibodies against influenza are rarely decreased during a pandemic. However, Salzberger asserts, “The fatigue from grafting in the fall and winter will be due to negligence.” “Every influenza vaccine improves our immune response to influenza infection and this is very important for high-risk patients.”

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