Following the detection of the first case of bird flu in humans and new infections in felines, the spread of the H5N1 virus is causing concern in the United States — but experts are refusing to panic.
US health authorities announced on December 18 that an elderly patient with underlying illnesses was hospitalized “in critical condition” in Louisiana with bird flu, a first in the country.
According to sequencing released yesterday, Thursday, a small portion of the H5N1 virus found in the patient’s throat has genetic modifications that may make it more adapted to the human upper respiratory tract (nose or larynx).
These mutations “probably arose during the replication of the virus in the patient,” the US Centers for Disease Control and Prevention (CDC) said.
“RNA viruses are known to mutate within their hosts, and these mutations are certainly worrisome,” Rebecca Christofferson, a researcher at Louisiana State University, told AFP.
But “the good news is that there doesn’t seem to be any evidence to suggest that the virus has become more contagious, as no other cases have been linked to it,” he said.
For several months now, the United States has been dealing with an epizootic – the animal equivalent of an epidemic – of bird flu.
The increasing number of mammals infected by the virus worries experts, who fear that a large circulation will facilitate the mutation of the virus, allowing it to be transmitted from person to person.
In the case of the Louisiana patient, the genetic mutations observed are “a necessary step for a virus to become more contagious,” but “not the only one” required, said Angela Rasmussen, a virologist at the University of Saskatchewan in Canada.
Similar modifications have been observed in the past in patients who were infected with the bird flu virus and became seriously ill, but did not necessarily lead to an increase in the transmissibility of the virus, experts remind.
For Tys Quicken, of the Erasmus University Medical Center in the Netherlands, these latest genetic mutations may also lead to less severe infections, with the virus becoming “more likely” to “infect the upper respiratory tract” and thus cause a runny nose and sore throat, despite the lower respiratory, and lead to pneumonia.
Apart from genetic mutations, what worries experts the most is the level of circulation of the virus.
In addition to the patient in Louisiana, 65 milder cases of the disease have been identified in people in the United States since early 2024, and others may have gone undetected, according to the CDC.
The circulation of the virus increases the chance of it mixing with that of seasonal flu, risking triggering a process similar to those that led to the 1918 and 2009 flu pandemics, according to Angela Rasmussen.
Health authorities are also keeping a close eye on the rise in cases of bird flu in cats.
In Oregon (northwestern USA), a cat died after eating raw animal feed, which was confirmed to be infected with the H5N1 virus by analysis.
Twenty felines infected with the bird flu virus have died at a shelter in the state of Washington (northwest USA), a local animal protection association announced on Facebook.
According to Angela Rasmussen, infected cats can put their owner at “risk” of infection during close contact.
Avian influenza A (H5N1) first appeared in 1996, but since 2020, the number of outbreaks in birds has increased greatly and an increasing number of mammals have been affected.
Source: APE – MEB
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