The US Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) today reported 3 more H5N1 avian flu outbreaks in dairy herds, raising the total to 49 in nine states.

Of the 3 newly reported events, 2 are in Michigan and 1 is in Idaho. Michigan now has 14 outbreaks, the most of any state, and Idaho has 5 affected herds.

A line list from the Michigan Department of Agriculture and Rural Development (MDARD) suggests that the latest detections are in Clinton and Gratiot counties. So far, H5N1 outbreaks have struck dairy herds in nine of the state's counties.

Tests on Canadian milk negative for H5N1 fragments

Given the H5N1 avian flu outbreaks in US dairy herds, Canada's government said yesterday that proactive monitoring of Canadian milk samples has turned up no evidence of the virus.

The testing was conducted by the Canadian Food Inspection Agency (CFIA) in collaboration with the Public Health Agency of Canada and Health Canada.

CFIA labs assessed 142 retail milk samples using polymerase chain reaction (PCR) testing, and all were negative. The PCR method can detect fragments of the virus, but it isn't able gauge the presence of live virus.

The World Health Organization (WHO) today announced that it has prequalified a second dengue vaccine, TAK-003, known as Qdenga and developed by Takeda. 

Qdenga is a live-attenuated vaccine that contains weakened versions of all four dengue serotypes. The WHO recommends its use in children ages 6 to 16 years old in settings where the dengue burden and transmission intensity is high. It is given in two doses, 3 months apart.

Prequalification means the WHO has assessed the quality, safety, and efficacy, and the step paves the way for countries and groups to buy the vaccine for a broader rollout. 

Step paves way for broader global access

Rogerio Gaspar, PhD, the WHO's director for regulation and prequalification, said Takeda's dengue vaccine is now eligible for procurement by United Nations agencies, including UNICEF and the Pan American Health Organization (PAHO). "With only two dengue vaccines to date prequalified, we look forward to more vaccine developers coming forward for assessment, so that we can ensure vaccines reach all communities who need it."

Brazil's drug regulators approved Qdenga in 2023, and, earlier this year, the first mass vaccination campaign launched in the city of Dourados in Brazil's Mato Grosso del Sul state.

The other prequalified dengue vaccine is Dengvaxia, made by Sanofi. It is given in a three-dose series, 6 months apart. It requires prevaccine screening and is given only to people who have had a previous dengue infection to avoid antibody-dependent enhancement, a phenomenon that makes repeat infections more severe and can cause severe illness after vaccination in those who haven't previously been exposed to the virus.

An international group of scientists estimates that the mean infection-to-symptom-onset incubation period of the 2022 global mpox outbreak was similar to that of previous outbreaks, but the onset-to-onset serial interval was about 5 days shorter in 2022. The serial interval is the time between when symptoms first appear in an initial patient and in the person he or she infects.

The findings are published in Emerging Infectious Diseases and may suggest that the shift to a predominantly sexually associated mode of transmission in 2022 may have influenced the serial interval, as well as more public health awareness and surveillance during the global outbreak.

Mpox outbreaks recorded since the 1950s have been defined by household transmission patterns and small case counts, but in the 2022 outbreak the virus became predominantly transmitted through sexual encounters between men who have sex with men. 

Shorter onset-to-onset by 1 week

In the study, the authors compared transmission and onset data in 15 studies with a total of 42 case records from pre-2022 mpox outbreaks with data from 42 relevant studies conducted during the 2022 outbreak. 

They found that the incubation period was 8.1 days in 2022 and 8.2 days in previous outbreaks, but the serial interval was 8.7 days in 2022 and 14.2 days in previous years.

Our study highlights the importance of monitoring temporal changes in transmission and disease progression.

The authors conclude, "Because estimated values of epidemiologic parameters are often used to inform interventions against a range of pathogens, our study highlights the importance of monitoring temporal changes in transmission and disease progression."