Coronaviruses, especially SARS-CoV-2, are pretty adept at jumping between different species, which is a concern. As written before in these pages, that means that animals can serve as a virus reservoir even after humans achieve herd immunity. Another concern around inter-species virus transfer that I raised earlier is that as viruses pass between species, they have a penchant for mutating and acquiring new behaviors and capabilities. This leaves to genetic chance the possibility of producing an even more virulent strain. It is a roll of the genetic dice as a virus randomly gains small mutations while it spreads.
On October 23, I wrote about how mink farms around the world have become CoV-2 hot spots. In that post, I mentioned that Denmark was particularly hard hit with animals catching the virus from their human handlers, causing the country to cull one million mink across several farms to prevent further spread of the virus. Well, in just two weeks, the situation has gotten much worse, leading to a new decision to cull the country’s entire population of 17 million mink as reported yesterday by Reuters.
Danish scientists found increased spread of the virus from mink back to humans, and the spread to humans involved a new virus strain that seems more resistant to human antibodies. The ongoing efforts to develop a vaccine are focused on viral strains that were isolated last Spring. If a new strain emerges that can avoid the immunity conferred by the vaccines under development, it could greatly reduce the ability of the forthcoming vax to give us significant herd immunity; in which case, we would need to develop another vaccine to handle the new virus strain, if possible. And while that vaccine is under development, what if yet another virus strain arises that resists that new vax? It would be a game of catch-up and extend the pandemic possibly by years.
This is the concern for viruses that jump between species. We will see.