In a new risk assessment, the World Health Organization (WHO) said two recent severe H5N1 avian flu infections reported from China and Vietnam are linked to the clade 2.3.4.4b, the strain currently circulating in multiple regions that has been linked to a few mild infections in Europe and the United States. The risk assessment's publication was first reported by Avian Flu Diary, an infectious disease news blog.
The case from Vietnam was initially reported in October in a 5-year-old girl from Phu Tho province who was seriously ill. It marked the country's first human H5N1 case in 8 years, but it wasn't clear if the new case involved the earlier clade or the more recent one. The case from China, reported in late November, involved a woman from Guangxi province who died from her infection.
Both patients had been exposed sick poultry. The Vietnamese girl had reportedly eaten the meat of sick chickens and ducks, and the Chinese woman had been exposed to live poultry before her symptoms began.
The cases lift the number of human infections from H5N1 clade 2.3.4.4b to six. The others were from the United Kingdom, the United States, and Spain, all of which were mild and involved people who had extensive contact with poultry.
The WHO said virus sequences, when available, showed no markers for adaptation to mammals or resistance to neuraminidase inhibitors. It warned that the virus continues to diversify and bears close watching. Though several mammals have been infected, the virus doesn't seem to be transmitting among mammals.
So far, the risk to humans remains low, and no sustained human-to-human transmission has been reported, the WHO said.
More outbreaks in poultry in multiple world regions
In the United States, four states reported more outbreaks in poultry, according to the latest updates from the US Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS). California reported an outbreak at a game bird farm in Glenn County, and Tennessee reported an outbreak at a backyard location producing eggs in Weakley County.
In Africa, Niger reported H5N1 in village birds, and in Europe, more outbreaks in poultry were reported from Poland, Spain, and Denmark, according to the latest notifications from the World Organization for Animal Health (WOAH).