- That is a good question. And like most good questions, it has no clear answer, says Tomas Bergström, professor of clinical microbiology at the University of Gothenburg.

Very simplified, he explains, a new virus that starts to infect can take three ways: the virus can die when a sufficiently large proportion of the population has become immune, the infection may remain low-intensive in smaller groups and cause new outbreaks, or the virus may become smaller aggressively and establish themselves as a common cold.

- Virus has no self-interest in putting it to its host, it just wants to spread. The driving force is then often that it becomes less dangerous. Because in general, the more moving the values ​​are, the more opportunities the virus has to spread, says Tomas Bergström.

The virus can remain for a long time

Joacim Rocklöv, professor at the Department of Public Health and Clinical Medicine at Umeå University, believes that the disease will persist for a long time to come. Efforts to stop the infection at national borders are thus really just a way to buy time, he explains.

This increases the possibility of developing a vaccine that can make a sufficiently large part of the population immune, so that the virus does not find new people to infect. At present, however, the researchers do not know how long the immunity is for covid-19.

"High proportion of infected" in simple computer models

Together with her research colleagues, Joacim Rocklöv creates computer models based on the knowledge available about the virus. The studies are not yet ready for publication, but they are beginning to see certain patterns in their calculations.

- When we run a first, simpler model for this disease, covid-19, it seems to be a high proportion of those infected, the vast majority actually. But in reality it is likely to be less extensive, because this simple model does not take into account all the details regarding the population, for example that different groups do not have direct contact with each other, what countermeasures are used and the like, says Joacim Rocklöv.

In addition, it may play a role if the virus is seasonal. Common flu viruses, for example, have their classic peaks in winter, but you still do not know how it is with this virus.