What is the H5N1 virus that experts warn about: symptoms and ways of spreading

From wild birds to mammals such as cows, cats or mice, and although the H5N1 virus is rare, it can affect humans.

Bird flu was recently discovered in the United States, prompting health authorities to take preventive measures to stop its spread. The virus is spread by wild birds and can infect domestic birds, and can also change and infect other animals or humans.

In March 2024, the virus was first detected in dairy cows. The Centers for Disease Control and Prevention reported at least 12 states where H5N1 bird flu has infected dairy cows. Only four people in the U.S. have tested positive for H5N1, three of whom worked for a dairy company.

In addition, a recent study published in the journal Nature documented the spread of H5N1 between flocks and infection in other mammals, including humans, indicating a “greater risk” to public health. On the other hand, bird flu in birds could have health and economic consequences due to production losses on infected farms.

Bird flu viruses have a greater ability to evolve and mix with other bird flu viruses. This increases the risk of new strains or more infectious strains emerging that could infect other species, including humans. The fact that bird flu is increasingly being detected in mammals is a trend that remains under close observation.

The European Centre for Disease Prevention and Control (ECDC) currently assesses the risk to the general population as low, and the risk to people who handle or come into contact with infected birds and mammals as low to moderate. Most strains of the bird flu virus are relatively harmless and do not infect humans.

However, some variants can develop mutations that increase their ability to infect other species, including humans.

Symptoms of bird flu infection in humans depend on the strain of the virus, but in the case of H5N1 they can resemble a cold.

Flu-like symptoms
The virus causes classic flu-like symptoms such as:

Cough
Diarrhea
Difficulty breathing
Fever above 38°C.
Headache
General discomfort
Muscle pain
Runny nose
Sore throat
How it spreads
The U.S. Centers for Disease Control and Prevention (CDC) explains that infected birds shed the virus through saliva, mucous membranes, and feces, while other infected animals may have viruses in respiratory secretions, organs, blood, or other body fluids, including the animals’ milk. The bird flu virus survives in the environment for a long time, up to 10 days.

Human infection can occur when the virus comes into contact with a person’s eyes, nose, or mouth, or when a person inhales particles of the virus. This can happen when the virus is released into the air (in droplets, small aerosol particles, and possibly dust) and lands on the mucous membranes of the eyes. It can also happen when a person touches an object contaminated with the virus and then touches their mouth, eyes, or nose.

Is it safe to eat meat and poultry products?
According to EFSA, there is no evidence that bird flu can be transmitted to humans through the consumption of contaminated poultry products. In all cases, meat and poultry products from infected flocks are destroyed and do not enter the food chain.

Safe handling of raw meat and other uncooked food ingredients, thorough food preparation, and good kitchen hygiene can prevent or reduce the risks associated with contaminated food.