– The reason why sars-cov-2 is difficult to eliminate, now resides in humans and not in animals. That’s what virology professor Espen Rimstad says.
The sars-cov-2 coronavirus originally came from bats. It is not clear how the virus jumped out of bats and became a pandemic. How and how often a virus is transmitted from animals to humans – a so-called zoonosis – researchers still don’t know enough.
– If you look at the genetic relationship, it indicates that sars-cov-2 originally originated in bats. We do not know if the virus came directly from bats, through another animal (intermediate host), or from a laboratory. But there is general agreement that bats are the original source, says the professor.
Professor Espen Rimstad works at the Norwegian University of Life Sciences in Ås. We have asked you some questions about human-animal transmission.
1. Has sars-cov-2 been found in wild species other than bats?
– One has no found a virus identical to sars-cov-2 in bats. But the sars-cov-2 that now circulates in humans is genetically closely related to a virus found in bats. Those viruses are very similar. But we are not sure if it was an intermediate host or not, an animal species that has transmitted the virus from bats to humans. We cannot rule it out.
2. What about infection in mice?
– Some variants of the sars-cov-2 virus have been detected in mice, but there are mice in the laboratory. Mice are a typical animal species, where an infection can be well maintained. There are many mice. They live together. For this to be a concern, an animal that is infected with sars-cov-2 must also be able to infect humans. Mink in Denmark and the Netherlands saw such a strong reaction that they could infect humans. But no matter how you change it, the number of animals infected with sars-cov-2 is small compared to people who become infected. Humans are the reservoir for this coronavirus.
3. How do humans become reservoirs for this coronavirus?
– Man is a numerous animal species. They are many and they can live and live together. There will be many who have not been vaccinated. Some are too young. Some live in countries with very little access to vaccines. This will be a very important reason why sars-cov-2 does not disappear. This means that the reservoir of sars-cov-2 will be in humans. And there are always people who travel and want to be able to take the virus to new places.
4. What do we know about the origin of this coronavirus?
– That the source is bats. There is a perpetual reservoir of sars-cov-2-like viruses in bats. They are one of the largest groups of animals that we know of. They are closely related in caves and caverns, often several different species together. A virus can be easily transmitted from one individual to another and from one species to another. If an animal species is to be a reservoir for sars-cov-2, there must be continuous transmission from one individual to another.
5. When is there a risk of the infection spreading between animals?
– There is no great danger of spreading the infection when an animal is not in any particular contact with other individuals of the same species. It is when animals live together that there is a risk of spreading the infection. So the concern is that the virus will establish itself in animals that humans are in contact with.
– We know that minks can get sick from covid-19, which can transmit the infection to other minks and to humans. We saw that viruses also mutate in mink. That is the real concern. Would the virus mutate into something less or more dangerous? A more contagious virus? Today, this is under control. In Norway, neither sars-cov-2 has been detected in mink from fur farms or in wild mink.
6. What does it take for humans to be infected by animals?
– The person must be in contact with the animal and exposed to a sufficient amount of the virus. The animal virus must recognize receptors on human cells (in humans) to enter cells.
7. What if the new diseases don’t seem to be the cause?
– When a new disease occurs in an animal species, it is the aspect of time which is important to prevent the spread of infection. It is important to act quickly and forcefully. This is what it tries to do when new livestock diseases occur. Technology is constantly improving, although we cannot monitor wild bats. We cannot prevent a new infection, but we can track it and detect it early if it occurs.