The US Centers for Disease Control and Prevention (CDC) today confirmed another human H5N1 avian flu case in California, which likely reflects follow-up testing of a presumed positive involving a San Francisco child. The latest confirmation puts the national total since early 2024 to 67 cases, of which 38 are from California.

San Francisco health officials announced the presumed-positive case, which involved a child with fever and conjunctivitis who was not hospitalized and has fully recovered, on January 10. Though most of California’s cases involve people with occupational exposure to sick dairy cows, the state has reported two illnesses in people with undetermined exposure sources, both of them children. The California Department of Public Health (CDPH) also updated its H5N1 total to 38 today, which adds a second illness from an undetermined exposure source.

In an updated risk assessment today, the CDC said the H5N1 risk to the general public remains low, but is higher in farm workers exposed to sick animals or their byproducts, backyard bird flock owners, animal care workers, and animal health and public health responders.

The CDC also spelled out the factors that would cause it to raise its risk assessment, including more efficient virus transmission, increased disease severity, more widespread cases, and great impacts from genetic changes in the virus. 

USDA confirms more detections in poultry and dairy cattle

In other developments, the US Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) confirmed more H5N1 outbreaks in poultry from three states. They include a broiler farm in Maryland’s Caroline County that has nearly 229,000 birds and two commercial turkey farms in Ohio, one in Darke County and the other in Mercer County, that, taken together, have about 15,000 birds. APHIS also confirmed the virus in a backyard flock in Phillips County, Kansas.

Also, APHIS confirmed 2 more H5N1 detections in dairy cattle, both in California, which pushes the national total to 927 and California’s total to 710.

A randomized clinical trial in the United Kingdom found that a procalcitonin-guided algorithm did not reduce the duration of intravenous (IV) antibiotics in hospitalized children compared with usual care, researchers reported last week in The Lancet Child & Adolescent Health.

The BATCH (Biomarker-guided duration of Antibiotic Treatment in Children Hospitalised) trial, led by investigators from UK universities and hospitals, enrolled children aged 72 hours to 18 years who were treated with IV antibiotics for suspected or confirmed bacterial infection at 15 hospitals. Of the 15,282 children screened from June 11, 2018, to October 12, 2022, 1,949 (median age, 3.1 years; 54% male) were randomly assigned to receive procalcitonin-guided therapy (977 children) or usual care (972). The co-primary outcomes were duration of antibiotic use (assessed for superiority) and a composite safety measure (assessed for non-inferiority).

The aim of the trial was to investigate whether the use of procalcitonin, a biomarker for bacterial infection, would safely reduce antibiotic duration compared with usual care, in which C-reactive protein is used to guide antibiotic therapy. The investigators hypothesized that because procalcitonin is a more specific host-response biomarker for bacterial infection, it might better facilitate decisions to de-escalate antibiotic therapy.

No evidence of treatment effect

But the results did not support that theory. The median IV antibiotic duration was 96 hours in the procalcitonin group and 99.7 hours in the usual care group (hazard ratio, 0.96; 95% confidence interval [CI], 0.87 to 1.05), providing no evidence of a treatment effect. Comparison of safety outcomes showed 9% of children in the procalcitonin group and 9% in the usual-care group had at least one event covered by the composite safety outcome measure (estimated adjusted risk difference, -0.81), indicating procalcitonin-guided therapy was non-inferior to usual care. 

Investigators also found that total costs were higher in the procalcitonin group, and that adherence to the protocol was low.

"Our results suggest that in hospitalised children treated with intravenous antibiotics for suspected or confirmed serious bacterial infection, a procalcitonin-guided algorithm is not effective in reducing intravenous antibiotic duration, especially where robust antimicrobial stewardship programmes are already implemented," they concluded.

Yesterday, the European Centre for Disease Control (ECDC) published an overview of imported mpox clade 1 cases in the European region. This clade of the virus is currently causing a widespread outbreak centered in the Democratic Republic of the Congo (DRC) and is different from clade 2, the virus that caused a global outbreak of mpox among men who have sex with men (MSM). 

The ECDC said there have been 11 cases in Europe since August 2024, all mild, though clade 1 is considered more transmissible and virulent than clade 2. The first case in Europe was a single case reported in Sweden in August 2024. Germany has had seven cases (one in October, five in December 2024, and one this month), Belgium reported two cases in December 2024, and France reported a single case this month. 

Of note, some cases in German and Belgium reflect household transmission, with children in each country infected via a household contact who had traveled abroad and contracted the virus. Outside of Europe, both China and the United Kingdom have reported similar cases of household transmission.

Overall risk remains low 

The ECDC said the overall risk to the population remains low. 

 It is important to note that close physical (skin-to-skin) contact or touching virus-contaminated materials is necessary to transmit MPX.

“Although significant uncertainties exist about the severity of mpox caused by MPXV clade I, most people experience mild to moderate symptoms, followed by a full recovery. It is important to note that close physical (skin-to-skin) contact or touching virus-contaminated materials is necessary to transmit MPX,” the ECDC said. 

In related news, the UK’s Health Security Agency (HSA) earlier this week released guidance on mpox clade 1 contact tracing.

“As soon as a patient has been confirmed as a clade I mpox case, all those who have had contact with the patient during their infectious period… should be identified (in some high-risk cases, identifying contacts may have begun before confirmation),” the guidance reads. 

The HSA categorizes three contact levels: high (unprotected direct contact); medium (unprotected exposure to infectious materials); and low (protected physical or droplet exposure). 

A hunter-harvested mule deer in the Hog Heaven Management Zone of Montana's Flathead Indian Reservation was confirmed positive for chronic wasting disease (CWD) on January 6, the Confederated Salish and Kootenai Tribes (CSKT) Division of Fish, Wildlife, and Recreation and Conservation (DFWRC) announced yesterday.

The reservation is located in the western part of the state on the Flathead River.

"The CSKT Wildlife Program is implementing the initial response protocol from the Tribe’s CWD Surveillance and Management Plan," the CSKT news release said. The response will include the collection of samples from 150 mule deer harvested from Hog Heaven and Irvine herds to determine CWD prevalence.

The CSKT Wildlife Program is implementing the initial response protocol from the Tribe’s CWD Surveillance and Management Plan.

"It is extremely important for the health of our Tribal people and our big game herds that any deer, elk or moose harvested from this area is tested for Chronic Wasting Disease before consumption," CSKT said. "There currently no vaccine for CWD, and if it were to spread to humans it would likely be through consuming infected meat."

CDC advises against eating meat from infected animals

CWD is a fatal neurodegenerative disease caused by infectious misfolded proteins called prions, which spread among cervids such as deer, elk, and moose and through environmental contamination. 

The disease isn't known to infect people, but experts fear it could cause illness similar to the prion disease bovine spongiform encephalopathy ("mad cow" disease). The US Centers for Disease Control and Prevention warn against eating meat from infected animals.