Bird flu in cows shows no signs of adapting to humans — yet

WASHINGTON — When traces of H5N1 bird flu showed up successful cow’s milk past year, it raised fears that nan microorganism could go much infectious to humans. So far, that hasn’t happened, virologist Richard Webby reported April 23 astatine nan World Vaccine Congress Washington.

Cows were astonishment hosts for nan virus. Influenza viruses latch connected to sialic acerb attached to sweetener molecules that decorate nan extracurricular of cells. It turns retired that nan measurement sialic acerb is attached to immoderate sweetener molecules connected cattle mammary gland cells resembles attachments, aliases receptors, successful birds. This statement allows nan H5N1 microorganism to infect birds and cows, said Webby, of St. Jude Children’s Research Hospital successful Memphis, Tenn.

Cattle besides person sialic acerb attachments for illustration those that flu viruses usage to drawback and infect quality cells. Researchers feared that having some humanlike and birdlike receptors successful nan aforesaid mammary glands mightiness make it easier for vertebrate flu viruses to adapt, making transmission betwixt group easier.

In cattle mammary glands, nan microorganism reaches levels that are astir arsenic precocious arsenic scientists tin execute successful a lab. “This is ‘kid successful a candy store’ if you’re a microorganism successful nan udders of these cows,” said Webby, who besides directs a World Health Organization halfway for monitoring influenza successful birds and animals. That giddy growth mightiness activity to humans’ advantage. “Within nan mammary gland of nan cow, these H5N1 [viruses] turn truthful good successful there, there’s nary existent unit connected them to change” to drawback nan quality receptor. “But that could alteration tomorrow.”

H5N1 successful cattle besides presents different danger, Webby said. The much people who drawback H5N1 vertebrate flu aft interaction pinch infected cattle aliases milk, nan higher nan chance of nan microorganism adapting to dispersed easy from personification to person. To date, 70 group successful nan United States person been infected, pinch 41 cases linked to vulnerability to dairy herds. One personification died after getting 1 of nan variants recovered successful cattle, though he caught it aft interaction pinch backyard chickens and chaotic birds.

Two versions of H5N1 avian influenza person infected dairy cattle successful nan United States. Many other mammals, including dolphins and porpoises, person besides been infected pinch related variants. Those marine mammals “were ne'er connected nan list” of animals that scientists thought vertebrate flu could infect, Webby said.

But nan wide assortment of mammals infected whitethorn not beryllium caused by a caller spot of nan virus, he said. “It’s conscionable that there’s truthful overmuch much microorganism around,” because it replicates to “ridiculous” levels successful nan birds and animals it infects.