When\u00a0H5N1 bird flu\u00a0first began infecting\u00a0U.S. cattle in early 2024,\u00a0diagnosis was elusive, because in\u00a0cows,\u00a0the\u00a0disease\u00a0looked completely different.\u00a0Instead of\u00a0affecting\u00a0the\u00a0lungs,\u00a0as\u00a0H5N1\u00a0does\u00a0in\u00a0other\u00a0mammalian\u00a0species,\u00a0it\u00a0caused\u00a0severe\u00a0infection in\u00a0the cows’\u00a0udders,\u00a0largely sparing\u00a0the lungs.\u00a0<\/p>\n
A study\u00a0by\u00a0University of Pittsburgh School of Public Health\u00a0researchers\u00a0published\u00a0today\u00a0in\u00a0Science Advances\u00a0provides the first mechanistic explanation\u00a0for\u00a0this\u00a0peculiar\u00a0new\u00a0guise\u00a0for H5N1, which\u00a0now affects\u00a0more than\u00a0100 bird and mammal\u00a0species globally.\u00a0The\u00a0study\u00a0also\u00a0establishes\u00a0a new\u00a0way to\u00a0help scientists\u00a0spot\u00a0bird flu’s\u00a0next surprise move\u00a0more quickly,\u00a0saving\u00a0precious time in\u00a0mounting\u00a0public-health\u00a0measures to stem the spread.\u00a0<\/p>\n
The disease first appeared in\u00a0dairy cattle\u00a0along the\u00a0Texas Panhandle\u00a0as\u00a0stubborn cases of severe,\u00a0necrotizing mastitis,\u00a0a\u00a0painful inflammatory condition\u00a0that\u00a0damages tissues\u00a0in the\u00a0mammary glands.\u00a0<\/p>\n
Mastitis is a classic disease in milk-production animals, and veterinarians were dutifully looking to all the usual suspects for the source, like bacterial pathogens. When the real culprit turned out to be bird flu, everyone in the field was caught completely by surprise. We hadn’t even remotely considered that cattle could be a host for H5N1.”\u00a0<\/p>\n
Suresh Kuchipudi, Ph.D., senior author, chair of Infectious Diseases and Microbiology, Pitt Public Health<\/p>\n
In\u00a0the weeks before the virus was\u00a0identified, it\u00a0moved from herd to herd, sickening\u00a0the cattle-and\u00a0contaminating their environments.\u00a0<\/p>\n
“If a cow is infected,\u00a0it sheds\u00a0a lot of\u00a0virus\u00a0into the milk,”\u00a0said Kuchipudi.\u00a0“This\u00a0raised concerns about occupational risk for farm workers.\u00a0Also, there is\u00a0a habit of feeding raw milk to domestic pets,\u00a0like cats, and there have been instances of\u00a0cats dying, which\u00a0we\u00a0studied\u00a0previously.”\u00a0He\u00a0stressed\u00a0that fortunately, pasteurization is\u00a0effective at killing the virus,\u00a0underlining\u00a0the importance\u00a0of avoiding raw milk.\u00a0<\/p>\n
Kuchipudi has been studying influenza viruses\u00a0for his entire career, with a\u00a0particular focus\u00a0on how\u00a0receptor biology\u00a0determines\u00a0which species-and which tissues-can\u00a0be\u00a0infected.\u00a0Typically,\u00a0such studies involve staining\u00a0cells\u00a0for\u00a0the presence of\u00a0receptors\u00a0that\u00a0are\u00a0known to\u00a0work in a lock-and-key relationship with influenza, a subset of sugar-based\u00a0molecules\u00a0known as glycans.\u00a0<\/p>\n