HAPPENING. Bird flu: why WHO is concerned about the risk of transmission between people and is sounding the alarm

After the Covid-19 epidemic, should humanity prepare for a new imminent danger? Last week, the World Health Organization (WHO) expressed “huge concern” about the increasing spread of the H5N1 strain of bird flu to new species, including humans.

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“During the current outbreaks, transmission of the virus from bird to cow, cow to cow and cow to bird has been documented, suggesting that the virus may have found other transmission routes than we previously thought,” Dr. Wenqing Zhang said. Heads the global influenza program at WHO.

First appeared in 1996

Recall that avian influenza A (H5N1) first appeared in 1996. However, since 2020, the number of outbreaks in birds has increased sharply, and an increasing number of mammal species have been affected. Last month, cows and goats joined the list. A surprising development for experts since they are not considered susceptible to this type of flu. Although the H5N1 strain has killed millions of poultry during the current wave, the affected cows have not become seriously ill.

In early April, US authorities reported that a person had tested positive for avian influenza after being infected by a dairy cow in Texas. The patient had “eye redness consistent with conjunctivitis as the only symptom,” authorities said, adding that he was isolated and treated with an antiviral drug used for influenza. “The Texas case is the first time a human has been infected with avian influenza from a cow,” recalls Dr. Wenqing Zhang, who clarifies that the virus does not currently show signs of increased adaptation to mammals.

Mortality rate 52%

According to experts, the virus can cause infection in humans if it is found in two very specific places: on the conjunctiva of the eye (this is a benign infection) or in the pulmonary alveoli, deep in the lungs. In the second case, the infection can be serious. In total, according to the WHO, between 2003 and 1 year, 889 cases of avian influenza were reported among people in 23 countries.^uh April 2024, including 463 deaths, resulting in a case fatality rate of 52%.

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In terms of human-to-human transmission, although no evidence has yet been provided, there are concerns that the H5N1 virus, which has shown “extremely high mortality” in people contracted through contact with infected animals, is mutating and becoming capable of transmission between men.

Contaminated milk

Another source of concern: the discovery last week of high concentrations of the H5N1 virus in the milk of cows infected with avian influenza in the United States. WHO has recommended sensible food safety measures such as using pasteurized milk. At the same time, studies are being conducted to determine how long the virus can survive in milk.

“The new H5N1 virus has mixed in the United States with local viruses and has the peculiarity of multiplying very well in the udder of cows,” Jean-Claude Manuguerra, director of the research unit Environment and Ecology, tries to explain. infectious risks” at the Pasteur Institute;

Do not panic

According to Bruno Lina, professor of virology at the University Hospital of Lyon, in an interview with AFP, we must avoid falling into psychosis. “Is finding traces of the virus in milk a warning sign? No, even if there is another animal that can become infected with this virus, it is not bad news. We risk seeing sporadic cases of infection emerge.” cases in both animals and humans. On the other hand, we are not seeing a serious modification of the virus that would lead to a higher risk of a pandemic than two or three months ago,” he reassures.

“Will a person exposed to unpasteurized milk contaminated with H5N1 develop an infection through the normal milk pathways (mouth, digestive tract, etc.),” continues Bruno Lina. Another encouraging factor is that the strain currently circulating in the United States is in any case different from the strains circulating in Europe.