Second US dairy worker contracts bird flu from infected cows

An electron microscope image showing an avian influenza A H5N1 virion
An eye swab confirmed the presence of the H5N1 virus, following conjunctivitis-like symptoms - Cynthia Goldsmith, Jackie Katz/CDC via AP

A dairy worker in the US state of Michigan has tested positive for bird flu, marking the second human case linked to the multi-state H5N1 outbreak among US cattle.

The worker contracted the illness from sick cows and has since recovered from the virus, state health authorities reported.

The man was said to have “regular contact” with bird flu-infected cattle. Of the now 52 dairy herds across the US affected by H5N1, 19 are located in Michigan.

This is the third human infection of H5N1 reported in the US since the highly pathogenic virus started circulating in 2020, killing millions of birds and mammals.

In March, a worker on a dairy farm in Texas became the first known person to contract bird flu from a mammal, rather than a bird, with genomic sequencing revealing the strain of the virus was derived directly from a cow.

In spring 2022, a man in Colorado was infected while involved in the culling of H5N1-infected poultry.

Both the farm worker and the patient in Texas experienced conjunctivitis-like symptoms in their eyes and no other symptoms.

For the most recent case, a nasal swab for H5N1 came back negative, while an eye swab confirmed the presence of the virus, raising concerns among experts that health officials might miss cases.

“The Centre for Disease Control laboratory is one of a few labs where eye specimens can be tested for H5N1 – this needs to be fixed, easier access to eye swab testing is needed to protect and diagnose farm workers,” said Dr Jennifer Nuzzo, Director of the Pandemic Centre and Professor of Epidemiology at the Brown University on X (formerly Twitter).

“If symptoms are mild and a person has ocular symptoms it could be attributed to a viral or bacterial conjunctivitis rather than considering testing for H5N1” added Dr Krutika Kuppalli, a spokesperson for the Infectious Disease Society of America and former WHO medical officer.

“The current health risk to the general public remains low,” Dr. Natasha Bagdasarian, chief medical executive at the Michigan Department of Health and Human Services said in a statement.

“This virus is being closely monitored, and we have not seen signs of sustained human-to-human transmission at this point,” she added.

Experts think it likely that we will begin to see more human cases of H5N1 in dairy workers in the coming weeks and months, as surveillance efforts ramp-up across America.

To help tackle reluctance in testing animals and people due to potential financial losses in produce, the US Department of Agriculture announced earlier this month a new support programme of up to $2,000 per affected farm for premises who facilitate testing of workers by local and federal public health bodies – in the hope it will help experts to better understand how the virus is spreading.

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