Avian influenza has been rampaging in wild birds around the world since late 2021. It can now be considered widespread in many types of wild birds, and has also spread to many other species including dairy cattle. Highly pathogenic forms of avian influenza, like H5N1, are thought to have caused the deaths of millions of birds around the world, both wild and farmed.
Scientists have recently found that one strain of this virus that is no longer in circulation was probably only a single genetic mutation from causing infections in people. Viruses have to enter cells to cause infection, and avian flu is particularly good at infecting bird cells, but is not that attuned to human cells. So while the illness can infect people who are in direct contact with infected birds, infected people do not spread the virus to other people, at this time. But this study, which was reported in the Proceedings of the National Academy of Sciences, showed that such possibilities exist.
"We were really shocked," said senior study author Robert de Vrie of Utrecht University. "It was very close. We do not yet know if this variant of the virus could have actually replicated in human cells. However, we do see that these viruses often already have the mutations that allow replication in other species. This is also what enabled them to spread so easily to other mammals."
Researchers have also found the genetic mutation that led to the infection of hundreds of dairy cow herds, and the culling of thousands of animals. It seems that one spillover event happened, in which a bird spread the disease to a cow, and then, the virus started to spread to other cows. These findings were published in Science.
After this initial spillover event, the virus quietly circulated among herds before it was confirmed in dairy cattle March 2024. It also began to infect cats, poultry, and raccoons, as well as some other types of wild birds like blackbirds and pigeons.
Dairy cattle continue to be infected with H5N1, and Idaho is the current epicenter of outbreaks. In the US in the past thirty days, 48 new cases of H5N1 have been confirmed in dairy cattle in Arizona (two new cases), California (six new cases), and Idaho (thirty new cases). Right now, the USDA is testing milk for H5N1 but unpasteurized milk or the equipment that is used to process it could harbor the virus. Drinking so-called raw (unpasteurized) milk comes with risks, and research has shown that many people are not aware of those risks.
The public also doesn't seem particularly worried about avian influenza, according to work reported in the American Journal of Public Health, and scientists are concerned that this could hamper efforts to contain the virus. Basically, if people don't know that it can be harmful, they are less likely to get a vaccine for the virus.
Experts are concerned about the rising threat of this situation, and have encouraged leaders to act now while we could still get the virus under control.
Unfortunately, public trust in scientific and health experts is also declining in the US. The World Health Organization has noted that vaccine hesitancy is also growing in many places around the world. This is threatening some public health efforts and increasing the risks of a variety of diseases.
One potential piece of good news reported in the journal Emerging Infectious Diseases, is that humans have been exposed to so many flu viruses and vaccines, we may be somewhat protected from H5N1 by these previous exposures and vaccinations.