COVID-19 has killed more men than women in Australia and claimed the lives of almost 10,000 more men than women around the world.

New figures have highlighted the trend, but scientists do not know why it is occurring. They initially pointed to men’s generally poor track record taking care of themselves – smoking too much, not washing their hands.

Are the differences in COVID-19 mortality rates down to our chromosomes?

But evidence is now mounting that these factors are not wholly to blame. Focus is moving to the very different immune systems of men and women.

"We know women end up with more auto-immune-type diseases, and men tend to do more poorly in several viral infections,” says Professor Gabrielle Belz, chair of immunology at the University of Queensland. "A lot of that is genetically encoded."