With outbreak of bird flu in cows in the USA, WHO issues warning about consumption of fresh milk

Last Friday, the 26th, the World Health Organization (WHO) issued a warning about the risk of transmission of H5N1, the virus that causes bird flu, through the consumption of fresh milk. The disease, which was initially known to mainly affect domestic and wild birds, has raised concerns due to its ability to infect an ever-increasing variety of species and the expansion of its geographic range.

Although the presence of the H5N1 virus has been detected in milk, it is still unclear whether the disease can be transmitted through consumption of this food. However, the WHO has requested that countries remain vigilant in the face of the possibility of transmission of the virus from animals to humans.

The alert was issued by the WHO after the Food and Drug Administration (FDA), a North American health surveillance body, announced the detection of fragments of the virus in one in every five samples of raw milk sold in the United States. Therefore, both bodies recommend the consumption of pasteurized milk, subjected to high temperatures to eliminate possible microorganisms, as a safety measure.

“Research into the virus detected in milk, as well as its potential role in transmission, is ongoing,” the WHO said in a statement.

The international entity recommends that countries implement infection control measures and reduce human exposure to birds and mammals possibly infected with influenza or other influenza viruses.

Before the discovery of fragments of the virus in milk, an outbreak of H5N1 was identified in 33 herds in eight US states, a fact that motivated the investigation into the milk.

At least one person in Texas was diagnosed with bird flu after having direct contact with reportedly infected dairy cows, but did not experience serious symptoms.

What is bird flu?

Bird flu is a highly contagious disease caused by variants of the Influenza virus. Currently, most of the cases with high transmissible potential in Brazil and other parts of the world are of the H5N1 strain.

To date, the disease has been identified in domestic and wild birds, livestock, and mammals. Humans can also contract it, although this is rarer.

First reported in 1878, in Italy, the “avian plague”, as it was known at the time, was only classified as influenza A in 1955. The first report of contagion by the H5N1 variety occurred in 1997, in Hong Kong. Brazil, until March 15, 2023, had never recorded outbreaks of the disease.

Brazil

According to March data from the Ministry of Agriculture, Brazil registered 158 cases of bird flu, 155 in wild birds and three in subsistence farmed birds.

Infectious disease physician Nancy Bellei, professor and head of the respiratory virus research laboratory at the Federal University of São Paulo (Unifesp), explained to Estadão that the current outbreak in Brazil and South America, regions where bird flu had not been detected previously, it is related to the development of a more pathogenic version of the influenza virus in migratory birds, which travel between countries in search of better living conditions.

How does transmission occur?

Nancy states that transmission to humans is considered rare, as they do not have the necessary receptors for the avian flu virus, unlike birds. However, this does not mean that the human population is immune to the disease.

The expert highlights that the risk of infection by H5N1 depends on the virus’s ability to undergo mutations that make it adapted to the human species.

Generally, transmission occurs through contact with secretions, blood, feces and even tissues from infected animals.

Nancy explains that, due to the history of contamination in humans, people tend to catch the disease when directly handling infected birds to prepare them for consumption.

Furthermore, transmission can also occur through aerosol particles released in the feces of sick birds, contaminating the air.

Symptoms

The symptoms of bird flu in humans are similar to those of the common flu, including high fever, muscle aches, back pain, headache, nausea, fatigue and respiratory symptoms such as cough and sputum. However, the condition can progress seriously, leading to breathing difficulties and even pulmonary hemorrhage. Furthermore, there are cases of asymptomatic infection, in which the patient does not show signs of illness.

In birds, symptoms can include problems with the nervous system and motor coordination, such as clumsy walking, reduced egg production (in laying birds) and large-scale deaths.

What to do if you are suspicious?

If a person is exposed to birds suspected or confirmed with H5N1, they must be monitored by the local health service, and isolated for 10 days, the virus’ incubation time (the period in which symptoms appear).

If the patient presents symptoms, it is necessary to collect secretions from the nasopharynx region – as done in Covid-19 with a swab – and remain isolated until the symptoms disappear.