The US Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) today confirmed five more H5N1 avian flu outbreaks in California’s dairy herds, bringing the state’s total to 105.

Centered in the state’s Central Valley, the dairy herd outbreaks began at the end August. The surge in outbreaks at dairy farms has come with a steadily rising number of infections in dairy workers, who have reported mild symptoms such as conjunctivitis. The US Centers for Disease Control and Prevention (CDC) has confirmed six infections, and follow-up testing is under way on five others identified during state testing.

Utah reports outbreak at Cache County poultry farm

Elsewhere, the Utah Department of Agriculture and Food (UDAF) reported the confirmation of highly pathogenic avian influenza in a commercial poultry flock in Cache County. In a statement, UDAF said the state veterinarian’s office was notified about symptomatic birds and immediately dispatched a team to assess the situation.

Utah reported its last avian flu outbreak in poultry nearly a year ago. Cache County is in northern Utah on the border with Idaho.

Yesterday the World Health Organization (WHO) announced the approval of Bavarian Nordic's mpox vaccine, Jynneos, for adolescents aged 12 to 17. 

The move comes as the outbreak in the Democratic Republic of the Congo is still raging, and infecting children at high rates. 

Seroprevalence study suggests many unreported cases

In other mpox news, a new seroprevalence study from German researchers publishing in BMC Infectious Diseases shows a high proportion of clinically undiagnosed mpox among Berlin’s population of men who have sex with men (MSM.)

The study was conducted between April 11 and July 1, 2023, and included blood samples from 728 participants, who were recruited from eight private practices and two community-based checkpoints in Berlin.

Only 70 (7.4%) participants reported a previous diagnosis of mpox. However serological testing revealed an additional 91 individuals with suspected undiagnosed mpox infection.

Men who reported condomless sex with multiple partners were most likely to have mpox, and a substantial proportion of mpox infections were clinically undiagnosed, the authors said. 

The authors said the findings were cautionary and suggest many more undiagnosed cases in MSM communities. 

 Many infections remain unrecognised and undiagnosed

"Mpox control measures based on clinical diagnosis of mpox are likely to have limited effectiveness in preventing mpox transmission in outbreak situations because many infections remain unrecognised and undiagnosed,” they concluded. 

A new study in The Lancet Infectious Diseases describes the genotypic and phenotypic characteristics of respiratory syncytial virus (RSV) breakthrough infections after the widespread use of the monoclonal antibody nirsevimab (Beyfortus) in infants younger than 1 year.

The study was based on outcomes seen among infants in France during the 2023-2024 RSV season, the first season the RSV antibody was approved for use in infants in the European Union and the United States. In France, roughly 210,000 single doses were administered last year.

To understand the real-life potential for viral escape, the authors looked at 260 RSV full-length viral genome sequences from nirsevimab-treated infants with breakthrough infections and compared the RSV RNA to that from 285 untreated RSV-infected infants.

In the breakthrough infections, 236 cases (91%) were RSV-A, and 24 (9%) were RSV-B.

Resistance only seen in RSV-B cases

There were no known nirsevimab resistance–associated mutations in infections caused by RSV-A, and only 2 of the 24 RSV-B infections showed a mutation that conferred resistance to nirsevimab.

Overall, breakthrough infections in France were rare, the authors said, and the antibody should be used again in the upcoming RSV seasons. 

As nirsevimab use becomes more widespread, collaboration between research and public health agencies becomes essential to assess the emergence of resistance.

In a commentary on the study, the authors write, "This finding underscores the need for subgroup-specific surveillance strategies to help better explain the different prevalences of monoclonal antibody-escape mutants between RSV-A and RSV-B. As nirsevimab use becomes more widespread, collaboration between research and public health agencies becomes essential to assess the emergence of resistance."

The Kentucky Department of Fish and Wildlife Resources yesterday announced the detection of chronic wasting disease (CWD) in a deer that died at a captive deer farm in Breckinridge County.

The Kentucky Department of Agriculture (KDA) confirmed the case, the state's first in a captive cervid facility, and has issued a quarantine restricting the movement of live deer or deer products to or from the farm.

"Kentucky Fish and Wildlife officials are in close communication with national, state and local partners and will reference the agency's CWD Response Plan in response to this new detection," the news release said. "Since 2002, Kentucky Fish and Wildlife has CWD-tested more than 40,000 deer and elk from across the state.​​​​"

The state's first CWD case was identified in December 2023 in Ballard County.

Hunters asked to participate in monitoring

Officials urge hunters to help with CWD monitoring by dropping off the heads of legally harvested and telechecked deer for free testing at self-service sample drop-off sites located throughout the state. 

Kentucky Fish and Wildlife officials are in close communication with national, state and local partners and will reference the agency's CWD Response Plan in response to this new detection.

CWD, a neurologic disease caused by misfolded infectious proteins called prions, affects cervids such as deer, elk, moose, and reindeer. Prions are extremely resilient and can persist in the environment for years. CWD poses an ongoing threat to cervids, because it can spread from animal to animal and through environmental contamination. The disease isn't known to infect humans, but officials recommend not eating meat from a sick animal and using precautions when field-dressing or butchering cervids.