A first serious case of avian flu (H5N1) was detected in humans in the United States this week. This is the 61st infected person in the country since April. A growing increase in cases which raises fears of a pandemic, although no cases of human-to-human transmission of the disease have been recorded.
Avian flu: risk level goes from “moderate” to “high”
- Why this increase in cases?
This increase in the spread of the virus – discovered 28 years ago – is explained by the arrival of a new variant on the American continent which has spread very quickly in wild bird populations over the past two years. The latter has the particularity of spreading very easily to mammals.
“This new virus has contaminated more than 50 different species of mammals”adds Professor Bruno Lina, virologist at the International Center for Research in Infectiology (CIRI) in Lyon.
Two subcategories of H5N1 are currently circulating across the Atlantic. On the one hand, one of them was transmitted to herds of cows by contamination through the latter's milk. In total, more than 600 herds in California alone were affected and 30% nationwide American. Extremely high concentrations of the virus have been found in marketed milk, contaminating one of the 61 cases recorded to date.
The other subcategory of this variant circulates mainly among wild birds. It is the main cause of serious cases of avian flu. Above all, its significant spread within this population makes scientists fear that the virus will be more easily mutated and, in fineto pass from one human to another, which may already be the case. At least three people have been infected in recent months by the H5N1 virus in the United States without knowing the origin of their contamination.
Avian flu: eagerly awaited by the foie gras industry, vaccination will start on October 1
- What are the symptoms?
The first symptoms are often similar to seasonal flu. The virus can thus cause cough, fever but also conjunctivitis. In more severe cases, H5N1 can also affect the lower airways of the lungs and lead to lung infection with difficulty breathing. The mortality rate can be extremely high in this case, “reaching 30% to 40%”specifies Professor Bruno Lina.
It is this second case which has caused concern since this week. The American over 65 years old contaminated and suffering from other pathologies is currently in “a critical state” et “suffers from a severe respiratory illness”Louisiana health authorities detailed to AFP.
- Do vaccines exist?
For the moment, several so-called “classic” vaccines already exist. Europe even ordered 665,000 doses last June British laboratory Seqirus. In total, 15 member states, including France, are participating in this joint purchase. They will be intended for the people most exposed to the virus, i.e. breeders or veterinarians. Several pharmaceutical laboratories are also working on research into messenger RNA vaccines. The latter have not yet shown their proof on seasonal flu. So last July, The World Health Organization (WHO) announced an initiative to develop messenger RNA vaccines in low- and middle-income countries in order to accelerate research on the subject. The project is headed by the Argentinian biopharmaceutical company Sinergium Biotech.
« The most important and most effective remain hygiene measures. The vaccination campaign is only planned if the protective measures are no longer sufficient and will only be initiated if there is human-to-human transmission. », clarifies Bruno Lina.
For the moment, vaccination of animals has been initiated in France. The government thus led a vaccination campaign in French duck farms extending from 1is October 2023 to September 30, 2024. The latter was renewed for 2024 and 2025. The first results are edifying: prevention through vaccination has made it possible to divide contamination on farms by 30.
