Third human case of H5N1 bird flu identified in US displays ‘respiratory symptoms’

A third dairy worker in the US has been diagnosed with H5N1 bird flu, this time with “respiratory symptoms” – suggesting the virus has got into their lungs.

The unnamed dairy worker from Michigan is the first US case to display acute respiratory illness from an H5N1 infection contracted from a cow. The two previous cases suffered only from conjunctivitis, an irritation and swelling around the eyes.

Influenza in humans typically spreads via respiratory droplets, for example through coughing or sneezing.  Now that the latest mutation of H5N1 has shown it can infect the upper respiratory tract, experts fear there is a greater risk of human-human transmission. 

“If we were to observe the gradual emergence of a new pandemic pathogen, these are the sort of signals we could expect to see,” Adam Kucharski, co-director of the Centre for Epidemic Preparedness at the London School of Tropical Hygiene and Medicine said on X (formerly Twitter). 

H5N1 – which has killed millions of animals since it began re-circulating in 2020 – has so far spread to 68 cattle herds in nine US states. 

Experts expect the human case number to rise significantly in the coming weeks, as state health authorities up their surveillance efforts to try and curb the spread. After a slow start, the US authorities recently instigated a program of financial incentives designed to get farmers to cooperate with testing. 

In Michigan, the state with the highest number of infected dairy herds, around 220 people are being monitored because of potential exposure to the virus, Dr Nirav Shah, deputy director of the CDC said at a briefing on Thursday 

The state is also beginning to conduct blood testing to see how many workers may have antibodies to the H5N1 virus, which would reflect past infections or exposures.

The CDC still considers the risk of H5N1 to humans to be low but has encouraged anyone who works directly with cattle or poultry to wear personal protective equipment (PPE) and report any symptoms to health authorities. 

Meanwhile, the US government is said to be in talks over a multimillion-dollar investment in mRNA H5N1 vaccines produced by Moderna. 

According to an unnamed source involved in the discussions, tens of millions of dollars of funding from the US Biomedical Advanced Research and Development Authority (BARDA) could be made available as soon as next month. 

The deal would include a commitment to stockpile millions of vaccines if the trials were successful, the Financial Times reported on Thursday. 

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