H5N1 grows well in dairy cow udders, which may actually be good news for people.
When traces of H5N1 bird flu showed up in cow’s milk last year, it raised fears that the virus could become more infectious to humans.
So far, that hasn’t happened.
Cows were surprise hosts for the virus.
Influenza viruses latch on to sialic acid attached to sugar molecules that decorate the outside of cells.
It turns out that the way sialic acid is attached to some sugar molecules on cow mammary gland cells resembles attachments, or receptors, in birds.
This arrangement allows the H5N1 virus to infect birds and cows.
Cattle also have sialic acid attachments like those that flu viruses use to grab and infect human cells.
Researchers feared that having both human-like and birdlike receptors in the same mammary glands might make it easier for bird flu viruses to adapt, making transmission between people easier.
