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Berlin – In connection with the H5N1 outbreak in dairy cows in the USA, a bird flu infection has been confirmed in a human for the third time. The person affected is once again a worker on a farm in the US state of Michigan who had contact with infected cows, the US health authority Centers for Disease Control and Prevention (CDC) announced yesterday.

There is no connection between the documented case in Michigan last week and the earlier detection in Texas. The virus was probably transmitted again from a cow to humans. The CDC also clarified that there were two different farms affected in Michigan.

According to the CDC, the patient has so far been confirmed to have an H5 infection, and further tests on the samples are ongoing. This is the first human case of H5 in the United States to report more typical symptoms of acute respiratory disease, the CDC explained. The patient had a cough and eye problems with watery discharge, but no fever.

The two H5N1 cases known to date in the USA had each developed conjunctivitis.

The worker who is now ill has been given the neuraminidase inhibitor oseltamivir and is isolating himself at home; the symptoms are improving, it was said. Household contacts of the patient have not yet developed any signs of illness and are continuing to be monitored. This also applies to all workers on the farm where the patient was infected. “There is currently no evidence of human-to-human transmission of A(H5N1) viruses,” the CDC emphasized.

The agency further stated that it would continue to closely monitor data from influenza surveillance systems, particularly in countries affected by H5N1, and that so far there have been no signs of unusual influenza activity in humans.

Based on the information available so far on the case, nothing has changed in the previous CDC risk assessment for the general population. It remains low for people who have no contact with infected animals. Nevertheless, the development underlines the importance of the recommended precautions for people who have contact with sick or possibly infected animals. These include wearing a respiratory mask and protective goggles.

The CDC also writes: “Given the extent of the virus spread in dairy cows, it would not be surprising to see additional cases in people who are at higher risk.” According to US authorities, almost 70 herds in nine states have now been proven to be affected. The CDC’s priority is to prevent further infections among workers on dairy farms.

Employees of poultry or dairy farms are recommended to be vaccinated with a vaccine against seasonal flu, according to the Michigan Department of Health and Human Services (MDHHS). Although this does not prevent infection with bird flu viruses, it can reduce the risk of co-infection with bird flu and flu viruses. According to experts, both types of viruses can mix in such cases – resulting in a potentially more dangerous pathogen.

In the current case, the determination of the neuraminidase of the influenza virus – the N in the name – is still pending, according to the CDC. Further genetic analyses are also being carried out to look for possible changes in the virus that could change the risk assessment. © ggr/dpa/aerzteblatt.de