Success through change

Viruses are masters of evolution. The new coronavirus is clearly very good at adapting to new hosts. Over the last few months it has also adapted specifically to humans as hosts.

Pandemics will occur more often in the future. This was the message issued by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) at the end of October 2020. The IPBES Workshop Report on Biodiversity and Pandemics states that the causes of pandemics are the same as the causes of loss of biodiversity. These include, above all, human invasion of previously intact ecosystems. Increasingly close contact between wild animals and farmed animals also play a role. IPBES recommends greater investment in measures to protect nature in order to counteract previous developments.

Kiel-based evolutionary biologist Professor Hinrich Schulenburg basically agrees with this view. "It is correct in that we are increasingly invading natural habitats where there are other mammals that also have viral infections. And, in principle, these can also cause infections in humans." What he has difficulty with, however, is the generalisation that such waves of infection are expected to become more frequent in the future. "We have had these kinds of waves of infection in the past. In principle, we must always expect viruses and pathogens in general to jump from animals to humans," said Schulenburg, who heads the working group Evolutionary Ecology and Genetics at the Zoological Institute at Kiel University. Viruses are survivalists. By constantly changing they adapt to conditions in their host and thereby ensure their continued existence. This rapid evolution enables viruses to jump from animals to humans and the other way round. Infectious diseases that can be transmitted between humans and animals are called zoonoses. They include rabies, ebola, HIV and the plague. And there are many indications that the Sars-CoV-2 virus also originated from animals. There are also, however, a few examples of animal diseases that are not transmitted to humans. These include European swine fever, canine distemper and bluetongue disease in ruminants.

It is not easy to predict which animal viruses may also become a danger to humans, however, as genetic changes in the virus happen by chance. Schulenburg: "What we have here are biological units that evolve in unpredictable ways. That is something that we have seen in the past and are seeing again now with Sars-CoV-2." The evolutionary adaptation of the new coronavirus is currently being investigated by various research groups around the world. They have ascertained, in particular, that there are mutations affecting the spike protein in the virus crown. The virus needs this protein to attach itself to cells and release its genetic material into the cells. “The new variants enable the virus to proliferate particularly well among humans, better than the original virus,” explained Schulenburg. There are also indications that in general the virus can adapt very quickly to new hosts, according to studies on minks. “The virus has jumped from humans to minks and there are now new variants within the virus population in minks that seem to have resulted in better adaptation to mink.” Millions of animals at mink farms were culled in order to prevent retransmission from mink to humans.

The latest data now indicates that the virus has adapted even better to humans and has spread more quickly and seems to cause more serious damage. "In principle, these types of evolutionary adaptations are always possible among pathogens," said Schulenburg. He is, however, confident about the imminent immunisation strategy: "Based on genome structure of the virus as well as the design of the approved vaccines, I am cautiously optimistic that we will not end up in the same situation as with the flu virus, where we need a new vaccine each year." According to Schulenburg, the changes that we know about and have detailed to date support the suggestion that the current vaccines will not lose their effectiveness, at least for the time being. “With the aid of the immunisation strategy it should in fact be largely possible to get to grips with the pandemic." Its success will depend on how willing the population are to being vaccinated, he said.

Author: Kerstin Nees