Who gets infected more often: people from animals, or animals from people?

About the circulation of viruses between animals and people. Many infections passed to people from animals. As an example, we can take the same coronavirus infection SARS-CoV2, the causative agent of the well-known COVID-19, or the deadly Ebola virus. These viruses naturally live in the bodies of bats. The pathogen can be transmitted from animals to people and back, or it can adapt to a new organism and “settle” in it.

If we are talking about viruses that rapidly multiply and transform, then a change in their “place of residence” can be determined by hereditary information in RNA or DNA. This method is suitable if there is a thoroughly read viral genome and data on the previous location of the virus, information about “relative” strains, variations, etc. All this is necessary in order to determine the degree of change in the infection.

However, if the pathogen can be transmitted from bats or other animals to humans, then does the same process occur, but in the opposite direction? Many people remember how the same coronavirus was periodically detected in pets whose owners were sick with COVID-19. Scientists explain: the virus, in the process of its transition from one organism to another, does not always undergo genetic changes - at least at the beginning. And it does not matter whether the pathogen has any mutations. The main point is its ability to settle and adapt to new structures.

Researchers recently analyzed how often viruses are transmitted from humans to animals and vice versa. Millions of virus sequences that had accumulated in various information databases were studied. As a result, it turned out that animals are more often infected from humans than humans from animals (the ratio was 64:36). Among the viral infections, coronaviruses and the causative agent of influenza type A were most often transmitted. However, even if these infections are removed from the list, the balance still tips toward infections of animals from humans.

As experts explain, the circulation of viruses between animals and people activates the evolutionary changes of the pathogen. At the same time, the infection, which is capable of living with equal potential in one or another organism, undergoes little change. Apparently, she already has a good degree of adaptation, formed earlier.

It is important to understand that mutual transmission of infection can lead to latent carriage and other problems. It is difficult to monitor such processes, but it is necessary. That is why the joint work of specialists from different fields, including biologists, zoologists, infectious disease virologists, veterinarians and ecologists is so important.

The full version of the article is presented on the page of the journal Nature Ecology & Evolution