Why have some people never been infected with Covid?

It can happen that quite a few people know someone who is not infected with Covid, despite the fact that everyone around them gets sick. Exactly why this happens remains a mystery, but scientists have begun to find some clues.

There is currently hope that identifying these mechanisms could lead to the development of drugs that not only protect people from Covid infection, but also prevent them from transmitting it to others.

"In our previous studies with other viruses, we have seen early nasal immune responses associated with resistance to infection," Professor Christopher Chiu of Imperial College London, who is leading a study in the field, told the Guardian. "Together, these data imply that there is a fight between the virus and the host, which in our 'uninfected' participants results in preventing the spread of infection."

Some of them reported some mild symptoms, such as a stuffy nose, sore throat, fatigue or headache - although, as these usually occur in everyday life, they may not have been related to exposure to the virus.

"Either way, the virus levels did not rise enough to affect the levels of antibodies, T cells or inflammatory factors in the blood that are usually associated with symptoms," Chiu said.

Other studies also suggest that it is possible for some people to "block" the virus during the earliest stages of the infection, before it forms a proper basis for symptoms.

Possibly, the memory cells associated with memory for previous coronavirus infections - that is, those responsible for common colds - reacted with the new coronavirus and protected these people from Covid.

A handful of people may even be genetically resistant to Covid-19. In October, an international team of researchers launched a global study to find some of them, hoping to identify protective genes.

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Source: Guardian