We've been talking about nothing else for weeks now. But what exactly is a virus?
The easiest way is to begin by explaining what a cell is. A cell is a small, living factory. It has a blueprint (recorded in DNA or genes), and according to this blueprint it produces everything it needs. All cells have two basic characteristics: they have an active metabolism and they can multiply by cell division. A virus is much smaller than a cell and has a much simpler structure. It consists only of a minimal blueprint (again from DNA or chemically related RNA) and a shell. On this shell there are small protein hooks.
The virus uses these to attach itself to the surface of a cell and then attempts to introduce its blueprint (DNA or RNA) into the cell. If it succeeds, the cell is infected and begins to produce new viruses according to the virus' blueprint. This is because viruses do not have their own metabolism and therefore need cells to multiply. Corona, for example, can work like this: I breathe in a virus that attacks a mucous membrane cell in my throat, which now produces its own viruses and these attack other throat cells. Soon I am carrying millions of viruses inside me, and when I cough, I become a virus slingshot myself.
Back to the infected cell: Sometimes something goes wrong in the factory. The blueprint is not copied exactly and a slightly altered virus is created: the virus has mutated.
Mutations do happen with varying frequency. Measles viruses, for example, hardly mutate at all. People who have had the measles or have been vaccinated can no longer be infected. The immune system knows the virus and fights it off. Flu viruses, on the other hand, often mutate. Our immune system must therefore adapt to the latest flu version every year.
Viruses are specialists: Their protein hooks only attach themselves to suitable surface proteins. These are not present on all cells and are different in humans and animals. Most types of viruses can therefore only infect one or a few related species.
Occasionally, however, it happens that a virus mutates in such a way that it can suddenly infect cells of another species. This is exactly what happened with the corona virus Sars-Cov-2: This virus, which specialized in bats, has mutated so that it can now attach itself to cells of our respiratory tract mucosa. SARS, MERS, Ebola, avian or swine flu have also spread in this way from animals to us. And unfortunately, this will also happen again and again in the future.
But finally something positive from the virus world. Their ability to enter cells efficiently is something we can exploit. In gene therapy - for example in the fight against cancer - "tamed" viruses are often used to introduce healing genes into the cells of patients. This is often the case: with sufficient knowledge and care, you can even benefit from a danger.
The article originally appeared in SonntagsBlick.