Avian Flu Diary: FAO Empres Watch: HPAI H5N1 In Dairy Cattle in The United States of America

#18,193

Although its cut-off date of July 11th means that it doesn't capture the latest 5 human H5 infections from Colorado, the FAO has produced a detailed report - aimed at an international audience - on what is known about the outbreak of HPAI H5N1 in dairy cattle in the United States.

Many countries appear to be taking a wait-and-see attitude towards the HPAI threat to livestock, believing this is a threat primarily to American cattle.

We've seen evidence, however (see Germany: FLI Statement On Experimental Infection Of Dairy Cows With European H5N1 Virus), that spillover of HPAI into cattle may occur even with European strains of the virus.

Due to its length (10 pages) I've only reproduced the summary below. Follow the link to download and read the report in its entirety.

Summary

The initial detection and subsequent spread of A(H5N1) in dairy cattle in the United States of America represents a key event in the ongoing evolution of highly pathogenic avian influenza (HPAI) viruses.
On 25 March 2024, authorities in the United States of America reported the detection of A(H5N1) in lactating dairy cattle. The virus affecting dairy cattle is a reassortant virus with both Eurasian HPAI H5N1 2.3.4.4b and North American gene segments. To date, it has not been detected outside the United States of America. This detection was in the context of a global surge in HPAI cases that started in 2021, associated with the ongoing evolution and spread of the H5N1 goose/Guangdong lineage viruses globally, such as the clade2.3.4.4b (Xie et al., 2023).
As of 11 July 2024, 145 dairy operations in twelve American states have been identified with the virus. On 1 April 2024, the same virus was detected in a farm worker in the state of Texas with presumed exposure to affected dairy cattle. This was followed by three additional cases among farm workers in the state of Michigan in May 2024, and Colorado in July 2024.
Two of these cases were mild with only symptoms of conjunctivitis, while the case in Michigan developed upper respiratory tract symptoms more consistent with the typical acute respiratory illness that is associated with influenza virus infection. No additional cases in humans associated with exposure to infected cattle have been reported at the time of writing.
Clinical signs in cattle are varied and include a decline in milk production with thickened milk consistency. Affected cattle appear to recover and reduce virus shedding after 2–3 weeks. Globally, scientists are working to address the numerous gaps that currently exist in our knowledge of the disease. The spillover event’s effects on dairy cattle health and milk production are still unfolding, with variable financial impacts at both the cattle and dairy market levels.
The World Health Organization (WHO) assesses the overall public health risk posedby A(H5N1) to be low. Still, individuals who may be exposed to infected birds or livestock should take appropriate precautions (FAO, WHO and WOAH, 2024). Countries are encouraged to increase their preparedness for HPAI outbreaks and work towards early detection and rapid response to spillover events in non-avian species. In areas at increased risk of HPAI outbreaks or viral circulation, enhanced biosecurity and surveillance are needed among all susceptible animals.