The California Department of Public Health (CDPH) reported today that the US Centers for Disease Control and Prevention (CDC) has confirmed two of its latest probable H5 avian flu cases, as it reported another likely case based on state testing, which if confirmed would raise the state’s total to seven.
California’s flurry of human cases is occurring amid an ongoing surge of outbreaks affecting the state’s dairy farms, which are concentrated in the Central Valley. Also today, the CDC shared the latest findings from genetic sequencing, which so far show no worrying changes.
Two patients worked on the same farm
Most of the earlier patients infected at California farms were from different facilities, but CDPH said two of the workers are from the same Central Valley farm. Both of them were exposed to infected cows, suggesting that only animal-to-human transmission is occurring in California.
The CDC said in an update today that the two people from the same farm worked on different parts of the farm, and aren’t close contacts of each other.
All six patients have experienced mild symptoms, including conjunctivitis. All were treated based on CDC guidance, and none were hospitalized.
CDPH added a seventh possible human case has been reported from the Central Valley and the specimen has been sent to the CDC for confirmation testing.
The new confirmations push the national total of H5 cases this year to 20. All but one are related to contact with sick cows and poultry. Health officials are still investigating the source of a human H5 infection in Missouri and whether illness symptoms in seven contacts, one household member and six healthcare workers.
No red flags in latest CDC sequencing findings
The CDC said it has now sequenced viruses from three patients, and all are closely related to viruses in dairy cattle.
Though the hemagglutinin of the three sequenced viruses has new amino acid changes compared to closely related candidate vaccine viruses, none are linked to increased infectivity or transmissibility among humans.
Also, sequencing hasn’t found any changes that suggest reduced susceptibility to antiviral treatments or any changes in other gene segments that would suggest mammalian adaptation.
CDC scientists successfully isolated the virus from California’s first two confirmed cases, and results are pending for similar work on other samples.
Dairy farm outbreaks reach 100 in California
In a related development, the US Department of Agriculture (USDA) Animal and Plant Inspection (APHIS) confirmed one more H5N1 outbreak in a California dairy herd, raising the state’s total since late August to 100, and the national total to 300 from 14 states.
California is the nation’s biggest dairy producer. The state has more than 1,100 dairy farms that house 1.72 million milk cows, according to the California Milk Advisory Board.
