Human contamination in the avian influenza outbreak in the United States

A person was infected with the H5N1 avian influenza virus in the US state of Texas. The Texas Department of Health reported this on Monday. According to authorities, the man or woman had direct contact with dairy cattle at a Texas ranch, where the cows were suspected of being infected with bird flu.

Last week the patient presented with complaints of eye redness and irritation (corresponding to conjunctivitis) as the only symptom. After testing positive, this person was advised to self-isolate to prevent infecting others. The man or woman was treated with the viral inhibitor oseltamivir and is now recovering.

Currently, the US Health Service's Centers for Disease Control and Prevention (CDC) maintains that the risk to the general American population remains low. However, people who are in close or prolonged contact with infected birds or livestock are at greater risk of infection and should take preventive measures. It is not recommended to consume raw milk products.

The first human being infected in the outbreak in the United States is not a surprise, but it is concerning because it is another step towards a form of bird flu that people can spread to each other. Last week, bird flu was reported for the first time on dairy farms in Texas and Kansas. The US Department of Agriculture (USDA) reports now It confirmed that the virus had infected livestock on farms in Texas (7), Kansas (2), Michigan (1), and New Mexico (1), while a farm in Idaho had a “suspected” outbreak. In Minnesota, goats died from the virus. Most likely, wild birds found dead on some farms have contaminated the animals' feed or water.

The outbreak in the United States is reminiscent of the outbreak of bird flu (with the H7N7 strain) that occurred on Dutch poultry farms in 2003. At that time, more than 450 people reported complaints and the infection was confirmed in a total of 89 people. Most of them had mild symptoms such as conjunctivitis and flu-like symptoms. One man, a veterinarian, died of pneumonia due to his infection with the virus. During that outbreak, there were indications that the virus spread on a small scale within households, because housemates also became ill.

The big difference between then and now was the source of the pollution. The H7N7 virus came from poultry, and human infection with H5N1 in the United States may have occurred via cattle. The risk is one step higher, because the idea is that by adapting to mammals, the virus could also become more infectious to humans.

The H5N1 avian influenza virus has been circulating among wild birds since 2020, and has since spread to almost all parts of the world. What makes this pandemic different from previous bird flu outbreaks is that waves of disease are no longer seasonal. In the past two years, the virus has been regularly transmitted from wild birds to land mammals, such as foxes, martens, and especially marine mammals.

The human infection now reported was not the first in the United States. In 2022, a man in that country was also infected with the H5N1 bird flu virus. It's about a prisoner in Colorado whose job it was to kill infected wild birds.

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