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.

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."

A single-center analysis published today in Travel Medicine and Infectious Disease finds that 86% of travelers returning to Spain with a chikungunya virus infection during a 2-year period reported joint pain that significantly reduced their quality of life. 

Researchers at La Paz-Carlos III University Hospital in Madrid, Spain, evaluated travelers who visited Latin American countries from April 2014 to September 2016, during outbreaks of the mosquito-borne virus. The median age of the 119 travelers was 41 years, 67.2 were men, and 25.6% had visited a travel clinic before departure.

In the United States, the Food and Drug Administration (FDA) approved Valneva's IXCHIQ chikungunya vaccine for adults in November 2023. In February 2024, the Centers for Disease Control and Prevention's (CDC's) Advisory Committee on Immunization Practices (ACIP) recommended the vaccine for certain travelers to affected world regions and chikungunya lab workers.

The most common symptoms of chikungunya are fever and joint pain, with the pain persisting from a few days to years. In unusual cases, death can result, usually in older people or children younger than 1 year.

Average duration of pain was 4 months

On average, the 102 joint-pain patients (86%) reported pain for 129.4 days. Risk factors for chronic joint pain were female sex, country of infection, older age, more than four symptoms during infection, high viral load, pain in previously injured tendons or joints, and certain lab markers.

Patients with chronic joint pain had to significantly adjust their normal daily activities, and 42.6% reported recurrence of symptoms after they had resolved. These patients said their symptoms improved substantially after they received tailored therapies.

Risk factors for chronic joint pain were female sex, country of infection, older age, more than four symptoms during infection, high viral load, pain in previously injured tendons or joints, and certain lab markers.

"The results of this study underscore the need for: (1) comprehensive pre-travel advice; (2) effective management of patients in specialized units, alongside early diagnosis and treatment, to prevent trivialization of these viral infections; and (3) the development of interdisciplinary recommendations to assist physicians in treating patients and enhancing outcomes," the study authors concluded.