Why are so many children sick right now?

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The situation is serious. An extremely large number of children are so ill due to severe respiratory infections that they have to be hospitalized. In the meantime, however, there are hardly any beds left for them. Some children's wards can no longer accept even the smallest patients. In addition to the children's wards, many pediatricians' offices are also overloaded. The vast majority of hospitalizations are due to the RS virus. RS stands for respiratory syncytial virus, or RSV for short. In addition, there are also cases of children who are severely ill from other cold viruses such as influenza.

Many RSV infections due to catch-up effect

But why are so many children sick all at once, and really badly? Martin Wetzke, a pediatrician and RSV expert at the Hannover Medical School, believes the reason is the so-called catch-up effect. This means that small children who were not infected with RSV during the last or even the penultimate RSV season due to corona protection measures have now fallen ill with it after all. Thus, several cohorts are ill at the same time, and thus the absolute number of those in whom the RSV infection is severe is also greater. This is usually the case with the first infection.

RSV is usually a classic respiratory pathogen. In most cases, the infection is accompanied by classic cold symptoms such as sore throat, runny nose and some coughing. "Eighty percent of children go through at least one RSV infection in the first two years of life," Wetzke says. About one-third of all children who get sick for the first time are taken to a pediatrician.

Two percent become so severely ill that they have to be hospitalized. RSV can cause severe pneumonia, also known as bronchiolitis. The risk is greatest for very young babies, especially premature infants. Young children with certain pre-existing conditions, such as severe heart defects and certain muscle weaknesses, are also more at risk.

According to Wetzke, 15,000 to 20,000 children fall seriously ill during a normal RSV season. Now, however, the season before last was largely cancelled due to corona protection measures. Last year, there was also a large RSV wave that started earlier than normal after the relaxations: as early as August instead of November. However, according to Wetzke, it did not run longer than usual and ended in December instead of March. As a result, there were no more cases overall than in a normal season. It remains to be seen how the current season, which started somewhat earlier at the beginning of October, will go.

"Every RSV infection acts as a booster".

According to Wetzke, a second effect could contribute to RSV accumulation: a lack of immunization in the womb. "Every RSV infection acts as a booster, and of course that also applies to mothers," the pediatrician said. If they go through an RSV infection during pregnancy, they can subsequently pass on their antibodies through the umbilical cord. If more mothers did not become infected during pregnancy due to masks and other protective measures, they do not pass on this season's antibody set.

According to Wetzke, it is not inconceivable that in some cases previous corona infections of the children could have weakened their immune system and made them more susceptible to infections. A similar effect is known from cases of influenza. However, this has not yet been proven.

Nor do experts see the "immune debt" currently circulating through the press and social media as the cause. This refers to a hypothetical weakening of the immune system due to the corona protection measures - because the immune system is said to have had no contact with pathogens. In fact, the immune system of the children reacts normally, especially since it had contact with all kinds of antigens and pathogens during the lockdown. However, it reacts to RSV with a time delay.

If you have to deal with the same type of virus more often, you are more likely to have many more up-to-date antibodies, says Reinhold Förster, head of the Institute of Immunology at the MHH, in a recent interview with Der Spiegel. Then it is easier to ward off colds completely, even before symptoms develop. If the contact has been longer or the viruses have changed more, however, you are more likely to fall ill.

Meanwhile, figures from the National Reference Center for Influenza Viruses at the Robert Koch Institute seem to suggest that notifications and positive rates for RSV are no longer increasing. Hopefully, this means that the RSV wave has peaked. Whether that can bring a rapid drop in severe cases and prompt relief for clinics is unclear. Experts also worry that influenza numbers will continue to rise, keeping clinics stretched to the limit.

(vsz)