In November, a Canadian teenager was hospitalized in Vancouver with a case of acute respiratory distress. The origin of his illness? The H5 virus, more commonly known as the “bird flu virus”. In his entourage, no other human contamination was detected, a sign that the virus is not yet transmitted from human to human. This week, a second serious case was reported in North America. This time it is a 65-year-old man living in Louisiana, more than 3,000 kilometers from Vancouver.
This man is the sixty-first case of human contamination in the United States since the start of 2024. In some cases, those affected suffered from a form of conjunctivitis, but fortunately, most people contaminated were asymptomatic. Still, the increase in cases of avian flu has alerted local public authorities, particularly in California, where 33 cases in humans have been reported this year. Gavin Newsom, the local governor, declared a state of emergency this Wednesday, December 18.
For the moment, the number of cases is still too low to speak of a human epidemic – including in California. But the United States is currently experiencing an epizootic of H5N1 avian flu, that is to say, an epidemic that affects animals. Since January 2022, there has been an explosion in cases of “highly pathogenic avian influenza” (HPAI), a particularly virulent form of virus, capable of decimating entire flocks of poultry in the space of a few days. . Such cases of the virus have been noted in all states: approximately 18% of American counties have been affected.
This epizootic has accelerated since spring and we have even observed a strong increase in cases among mammals (particularly among cattle). The thirty human cases detected in California are believed to be due to transmission between mammals and not to contamination from poultry to humans, as is generally the case. The disease is circulating more and more actively: of the 868 herds of dairy cows where the presence of the virus was detected, 175 were between December 1 and 16. For this reason, health authorities fear a virus mutation which could have facilitated this transmission between mammals and which, ultimately, could even allow the transmission of the virus from human to human. For the moment, no such cases have been reported across the Atlantic.
Despite this increase in cases and increased vigilance, the Centers for Disease Control and Prevention (CDC) network believes that the current public health risk is low.