Could Bird Flu Trigger a Human Pandemic? Experts Warn of Rising Risks

It’s been ten months since scientists discovered that a virus typically found in wild birds can infect cows. So far, at least 68 people in North America have fallen ill, and we’ve seen one confirmed death.

Many infections have been mild, but troubling trends are emerging. Certain strains of the H5N1 avian flu virus that are spreading in North America have been linked to serious illness and can even lead to death if passed from birds to humans. This virus is also learning to thrive in new hosts like cows and other mammals, which raises the risk of a potential human pandemic.

“The risk is growing, especially with recent reports of severe infections,” explains Seema Lakdawala, an expert in influenza at Emory University.

Recently, US President Donald Trump announced the country would withdraw from the World Health Organization, raising concerns among scientists about the spread of bird flu.

Nature spoke with infectious disease specialists to understand more about how the virus infects humans and the potential for a bird flu outbreak.

Does the source of infection matter?

Researchers are focused on two main strains of the virus. One called B3.13 is primarily affecting cows, while the other, D1.1, is mainly found in birds, including poultry. B3.13 is rapidly spreading among cattle in the US, affecting over 900 herds across 16 states. It has also infected other animals such as cats and skunks.

Cows infected with this virus produce milk with high levels of the pathogen, making it easy for dairy farm workers to become infected. Although about 40 people have contracted the virus from cows, most only experienced mild respiratory illness or eye irritation. On the other hand, 24 individuals became ill after contact with birds, with two severe cases leading to extended hospital stays and one fatality.

While the numbers are too small to draw firm conclusions, factors like existing health conditions and how the virus is contracted could influence treatment outcomes.

Is the method of exposure important?

Dairy workers face a higher risk because they may inhale virus-laden droplets during milking. Some research suggests that direct inhalation might lead to more severe disease. A study published in Nature examined monkeys infected with the B3.13 strain and provided insights into how the virus behaves in different hosts.