That’s why diseases are putting us to bed so hard this winter – spoiler: pandemic

We will probably tell our grandchildren about Christmas 2022, when half the family coughed at the dining table or a floor up in bed cured the fever. Now the number of virus particles in the wastewater is falling again: flu, RS viruses and corona are decreasing. This is also evident from the latest wastewater figures. But there is still a striking number of absences from work due to a wide variety of infections, from middle ear to pneumonia to tonsillitis. And many say, “I’ve never had such a persistent cough.”

The wave of illness is not over yet: the flu is followed by bacterial infections, for example with pneumococci. As evidenced by the reported cases, the number of pneumococcal infections is currently rising sharply. “There have certainly been some tough weeks in the past, but we obviously have a lot of cases right now,” said Urs Karrer of Winterthur Cantonal Hospital.

As an infectious disease specialist, Karrer knows this trade-off: after every flu outbreak, pneumococcal infections increase. These bacteria often colonize us, but it only becomes dangerous when they penetrate deep into the lungs, blood or even the brain. “Pneumococci have a mortality rate of about 10 percent there,” says Karrer. Treatment with antibiotics does not always work in time. Babies, small children and the elderly are particularly at risk. Since 2019, pneumococcal vaccination is part of the basic vaccination plan for two-month-old children.

“If the flu virus has damaged the epithelium of the mucous membranes, pneumococci can enter more easily,” explains Karrer. After the corona waves, there was no such effect in pneumococci, flu seems to pave the way for these bacteria particularly well.

During the pandemic, the term “immune debt” was coined for this, but it can be misleading because any infection poses a risk to the individual and is not something to be desired. “Immunity Gap” is slightly better and refers only to the entire population, which has become more susceptible to pathogens.

There are two explanations for the extraordinary wave of illness, but only the first is correct: due to the corona measures, the population came into much less contact with the viruses that usually circulate for two winters. This has not damaged our immune system in any way, but as a result our immune memory has not been refreshed for a long time and the body is currently less likely to fight against the pathogens.

For example, before the pandemic, about 5 to 20 percent of the population caught the flu during the annual flu outbreak, according to Germany’s Robert Koch Institute. But by no means all infected people stay in bed because of this: many infections are asymptomatic, but probably leave a stimulating effect in the immune system.

Children up to two years had no immunity at all. These became ill with RSV both in summer and at the beginning of winter. Then came the flu. For example, there were many more small children in this flu wave who without protection boosted the infection.

In addition, there are older children who were already infected with the various viruses before the pandemic, but whose protection against the single infection was not very strong. These too had a higher risk of becoming ill and infecting others in recent weeks. And: because pregnant women no longer came into contact with the pathogens, their newborns were born with weaker nest protection.

The second reason for the wave of illness could be a late consequence of the many corona infections this year. This is conceivable, but not yet proven. Infectiologist Karrer says: “At the moment there is no evidence for that.”

It is known that after a measles or yellow fever infection there is a long-term but temporary weakening of the immune system. Measles infection can erase large parts of the immune system’s memory, which can leave you more susceptible to later illnesses.

Austrian virologist Lukas Weseslindtner also told a Viennese newspaper that people who got sick with Covid-19 were no more likely to get respiratory infections than those who weren’t infected.

The Zurich immunologist Christian Münz also sees no signs that Corona could weaken the immune system as a whole, as is the case with AIDS: “After a coronavirus infection, the T cell reaction takes place against different fragments of the virus. So these memory cells store different pieces of the virus in each person, so the virus cannot escape the immune memory.”

In the case of HIV, this is only possible because the virus variants are produced in humans themselves and can therefore change the virus fragments that are recognized by the T cells in every human being. Karrer says, “We would have seen an effect like that a long time ago with Sars.”

Yet the interpretation of the disease wave is often ideologically colored: those who hated the pandemic measure now blame them for the many infections that have caught up. However, Karrer points out that the effect of the corona measures on other diseases was not harmful at all, but sometimes relieved hospitals of extra patients.

However, the current wave of illness was and is a risk for newborns: RSV viruses in particular are particularly dangerous for the little ones and it has been difficult to protect them in recent weeks. When they have to go to the hospital, they encounter overcrowded emergency rooms and overworked staff. And if a large number of sick people require medical care at the same time, the quality of treatment may deteriorate.