Why one patient dies and another doesn’t?

Beeld Van Santen & Bolleurs

The coronavirus comes in many guises. Some get a runny nose and others become deathly ill. How is that possible? It seems to be a macabre game of genes, lifestyle, the immune system, living conditions and underlying diseases.

With a cold and some fever, Piet van Treijen (103) from Steenbergen bumped through his Covid-19 in two weeks. Yes, he was weakened, but it was not much more. He soon felt patent enough for a young gin. More than a century old and able to withstand the potentially fatal disease.

A miracle?

No, because a 102-year-old woman in a bright blouse walked out of the hospital in Capelle aan den IJssel after a short illness.

And they weren’t the only centenarians to get Covid-19 underneath.

A brat. Maybe some loss of taste and smell. Or simply no response, that is also possible. Hordes of people barely notice that the potentially deadly coronavirus has entered their bodies. At the other end of the spectrum are the six to nine thousand Dutch people who did not survive the virus.

What’s up with that? Why does one get sick of this virus and the other not? Why do apparently fit and young people also end up on ventilation in intensive care? Scientists are breaking their minds about that question.

For the time being, there are only first few pieces of information that outline some contours. For example, it was announced last week that it is partly hereditary determined whether someone is very sick from Covid-19. An international research group found two specific places in the DNA of Italian and Spanish (ex-) covid patients that cause people to have an increased risk of becoming seriously ill.

“You also get the increased risk of becoming seriously ill from Covid-19 from your parents,” says professor of genetics Lude Franke of the UMCG in Groningen, who is indirectly involved in this study.

Some perspective is appropriate, Franke emphasizes, because even if you have a bad genetic starting point, that does not mean that you really get sick from the virus. Lifestyle and living conditions also play an important role.

Very overweight

At the beginning of the epidemic it became clear that the elderly and people with cardiovascular disease, diabetes and lung diseases are more at risk of a serious course. Later, the intensivists noticed that there were also many people who were very overweight on the ventilator. British research showed that 70 percent of the patients on the IC were overweight. Smokers also have worse cards.

Men are also more affected by the virus: of the approximately 12,000 people who had to be hospitalized with Covid-19, almost two thirds were men (61 percent), according to figures from the RIVM. Men not only get sicker than women, they also die more often. Of the more than 6,000 corona deaths registered, 55 percent were men.

This is not entirely surprising, because men more often have underlying diseases that increase the risk of a serious course. At the same time, women have an additional advantage because they have a defense system that is better able to cope with viruses. Children are known to have, on average, little trouble with a virus infection.

Professor of immunology Huub Savelkoul of the University of Wageningen is not surprised by the large individual differences. “You see them more often in infectious diseases. This is mainly because the immune response to that infection varies from person to person. ” What plays a part, according to “a wonderful paper” by American researchers, is which cold viruses someone has gone through.

The research focused on T cells, which can kill virus-infected cells and instruct B cells to make antibodies against the virus. So those T cells are crucial. Well, those cells also have a memory: if they recognize the virus from the past, they act more quickly and they switch off the virus faster.

Innocent cold viruses

The coronavirus that causes Covid-19 is part of a family of coronaviruses, which also includes four relatively harmless cold viruses. “They are responsible for 35 percent of all common colds,” says Savelkoul. “Those viruses are a bit like the new corona virus. Imagine that one virus is wearing a green jacket, another virus is wearing a red jacket, yet another is wearing a yellow, orange or blue. At some point the color no longer matters and the immune system recognizes a jacket and then it makes antibodies. This is also how it works with the new corona virus. They call it a cross-reaction. That’s not the same as immunity, but a cross-reaction means you also have a chance to get some protection against that virus. ”

Savelkoul also saw that in Dutch studies. In people with a proven infection with this coronavirus, 83 percent had a T cell response. However, 34 percent of the non-infected also had such a reaction. “Most likely because they had colds with coronaviruses in their lifetime.”

Can’t you get infected? “We don’t know,” says Savelkoul. “A nice parallel is that with HIV. At the beginning it was thought: if you are infected, you also get AIDS. But many years later, researchers discovered that there were people with a certain type of tissue type that made them naturally resistant to the development of AIDS. ”

Savelkoul does not know whether this is also the case with the new corona virus. But it is striking that it seems to hit less hard in certain parts of the world, for example in Africa. “We know there are differences in the hereditary build-up of the immune system in black people versus white people. Coincidentally, is there also the difference in genes that are important in the resistance to this virus infection? ”

Regional differences

But Savelkoul sees more striking regional differences. He is also amazed at the various mortality rates within Europe. “If you compare Italy to Germany, for example, it is quite special that in both countries about 20 percent of the population is older than 65, but the chance of dying from a corona infection is about 15 percent in Italy and in Germany. 5 percent. So age is an important factor, but not everything. Perhaps the factor is that houses in Italy are smaller than in Germany. People live closer together. ”

Jochen Mierau, professor of economics of public health at the University of Groningen and scientific director of the Aletta Jacobs School of Public Health, adds that the differences are also large within countries. With Lude Franke, he zooms in on the Lifelinescorona study on why one gets sicker from the virus than the other. Where Franke focuses on the genetic story, Mierau pays attention to socio-economic aspects. The first results are not expected until autumn, so Mierau is currently drawing on international studies. “The risk of death of someone living in a disadvantaged neighborhood in England is twice as high as that of someone living in a prosperous neighborhood. That cannot just be due to the lifestyle. ”

According to Mierau, corona is “magnifying social inequalities.” “That is what the virus does first, which will also be the case with the consequences of the measures, and then, if the recession really hits, it is that group that is affected again. We do not have much control over the virus, but we do have influence on the measures and how we deal with the recession. You have to protect those groups against that.

 

By / Het Parool from Dutch translated by google.com