• In China, the first death from the H3N8 strain of avian influenza was recorded.
  • In Chile, an avian influenza sample taken from a patient infected this time with the H3N8 strain indicates that the virus contains two mutations indicating an ability to adapt to mammals.
  • Should we fear an avian flu pandemic?

Cases are sporadic, but there appears to be increasing human contamination by avian influenza. In China, a woman died after contracting the H3N8 strain of the virus, which has been circulating since 2002 and had so far caused no known human casualties, the World Health Organization (WHO) said a few days ago. Meanwhile, in Chile, scientists discovered in a man infected with the H5N1 strain of avian influenza that he was carrying a virus with two genetic mutations, likely to make it more transmissible to humans.

What do these contaminations mean? Could a mutant strain of bird flu cause a pandemic? 20 Minutes takes stock of what is known about the virus.

What is known about the H3N8 strain of the virus?

The H3N8 virus, which first appeared on the North American continent, was previously considered to be susceptible to transmission to horses, dogs and sea lions. It had not been detected in humans until the first two non-fatal cases in China in April and May 2022.

The deceased is a 56-year-old resident of southeast China's Guangdong province. She became ill on 22 February, was admitted to hospital with severe pneumonia on 3 March and died on 16 March, according to WHO. "The patient had multiple predispositions. She had a history of exposure to live poultry before the onset of the disease, and a history of wild birds around her home," the organization said.

Attendance at a live bird market may have caused this contamination but "the exact source of this infection remains to be determined, as well as the link between this virus and other avian influenza type A (H3N8) circulating in the animal environment," added the WHO, calling for research on the issue. The organization stressed that the available data showed that this virus was not transmitted between humans and that, therefore, "the risk of its spread at the national, regional and global levels is considered low". However, WHO reiterated the need for constant surveillance due to the permanent mutations of viruses.



What are the particularities of the H5N1 strain, identified in a man in Chile, and where is it rampant?

Another country and strain: In Chile, a 53-year-old man was infected with the H5N1 strain of the virus in March. A sample taken from the patient revealed that the virus he contracted contained two genetic mutations indicating adaptation to mammals, officials from the Centers for Disease Control and Prevention said a few days ago. Studies have shown that these mutations, observed in the PB2 gene, help the virus replicate better in mammalian cells.

And in recent years, H5N1 has spread across the globe. Since October 2021, "Europe has been suffering the most devastating epizootic [animal epidemic] of highly pathogenic avian influenza it has ever known," recalls Public Health France. Numerous outbreaks, mostly due to the H5N1 virus, have been identified in domestic poultry and wild birds, resulting in the culling of several million birds. The geographical extent of this epizootic is also unprecedented, with almost all continents affected, in particular Europe, Asia, the Americas and to a lesser extent Africa."

In France, "315 outbreaks in livestock have been confirmed since August 1," says the Ministry of Agriculture. And in wild avian fauna, "the number of cases has also risen sharply in France in 2022-2023 with hundreds of infected birds found dead on the territory, and an endemization of avifauna infection that extends to non-migratory birds," adds Public Health France.

Is there a risk of human-to-human transmission, or even an avian flu pandemic?

"While most avian viruses do not infect humans, some subtypes sometimes manage to cross the species barrier: this is the case of the H5N1 virus, a pathogen for humans and present in Asia," recalls the Institut Pasteur. At present, the transmission of the virus is only from animals to humans, but health authorities fear an evolution of the virus into a form transmissible from human to human, an open door to a pandemic. "

The risk in the general population remains low, health officials in Chile have said, and no additional human cases have been linked to the infected man, who remains hospitalized. This news is all the more reassuring because the sample taken from the patient indicates that the virus does not carry other genetic mutations that would help it spread better among humans. "There are three broad categories of changes that we think H5N1 needs to go through to move from an avian virus to a human virus," Richard J. Webby, an avian flu expert at St. Jude Children's Research Hospital in the United States, told The New York Times. The sequences of the virus identified in the patient in Chile carry only one of these categories of changes. The easiest to implement for the virus. For Anice C. Lowen, a virologist specializing in influenza at Emory University, also in the United States, these mutations observed are "like a step on the way to adaptation to humans and an increased risk for humans. So it's certainly worrying to see them."

A "threat" deemed "real" by the Institut Pasteur: "The spread of infection in birds increases the likelihood of the appearance of a new influenza virus in the human population. In addition, the subtype has a high ability to mutate over time, but also to exchange its genes with influenza viruses belonging to other infective subtypes of other species. The risk of a new virus capable of human-to-human transmission is to be taken into consideration. However, the Institut Pasteur points out, "the appearance of an influenza virus belonging to a viral subtype totally unknown to the human population, such as H5N1, renders the population's immune memory ineffective. This is in favor of a pandemic." But for now, the WHO considers that "the risk of transmission to humans of avian influenza viruses circulating at present is low, and no human-to-human transmission has been documented".

  • Health
  • Avian influenza
  • China
  • Virus
  • Chile
  • Poultry
  • WHO