‘Worrying’ mutations in H5N1 bird flu virus found in Canadian teenager

The fate of a Canadian teenager who was infected with the H5N1 bird flu in early November and was subsequently admitted to intensive care is finally known: she has fully recovered.

But genetic analysis of the virus that infected her body showed threatening mutations that researchers said may make the virus more easily target human cells and cause serious illness – a development the study authors called “worrying.”

The case was published Tuesday in a special issue of the New England Journal of Medicine, which examined H5N1 cases from 2024 in North America. In a study, doctors and researchers who worked with the Canadian teenager published their results. In the other case, public health officials from across the U.S. — from the Centers for Disease Control and Prevention and state and local health departments — recorded the 46 human cases that occurred between March and October.

In 2024, a total of 66 human cases of H5N1 avian influenza were reported in the United States.

In the case of the 13-year-old Canadian child, the girl was admitted to a local emergency room on November 4 after suffering from conjunctivitis (conjunctivitis) in both eyes for two days and a fever for one day. The child, who had a history of asthma, elevated body mass index and grade 2 obesity, was discharged without treatment that day.

Over the next three days, she developed a cough and diarrhea and began vomiting. She was brought back to the emergency room on November 7 with shortness of breath and a condition called hemodynamic instability, in which her body was unable to maintain constant blood flow and pressure. She was hospitalized.

On November 8, she was transferred to the pediatric intensive care unit of another hospital with respiratory failure, pneumonia in the left lower lung, acute kidney injury, thrombocytopenia (low platelet count) and leukopenia (low white blood cell count).

She tested negative for the predominant human seasonal influenza viruses but had a high viral load of influenza A, which includes the major human seasonal influenza viruses as well as H5N1 avian influenza. This finding prompted her caregivers to conduct an avian flu test. she tested positive.

As the disease progressed over the next few days, she was intubated and placed on extracorporeal membrane oxygenation (ECMO) – a life-support technique that temporarily takes over the function of the heart and lungs in patients with severe heart or lung disease.

She was also treated with three antiviral medications, including oseltamivir (brand name Tamiflu), amantadine (Gocovri), and baloxavir (Xofluza).

Because of concerns about the possibility of a cytokine storm — a potentially fatal condition in which the body releases too many inflammatory molecules — she was placed on daily plasma exchange therapy, in which the patient’s plasma is removed in exchange for donated health plasma.

As the days went by, her viral load began to decrease; On November 16, eight days after her admission, she tested negative for the virus.

However, the report’s authors found that the viral load in their lower lungs remained consistently higher than in their upper respiratory tract – suggesting that even after the disease disappears, it could manifest itself in places not currently tested for it (e.g. B. in the lower lung). of those being tested (such as mouth and nose).

She made a full recovery and was discharged sometime after November 28, when her intubation tube was removed.

Genetic sequencing of the virus circulating in the teenager showed that it was similar to the virus circulating in wild birds, the D1.1 version. This is a type of H5N1 avian influenza that is related to, but distinct from, the type found in dairy cows and is responsible for the vast majority of human cases reported in the United States – most of which were in dairy cows or transferred to commercial poultry. This is also the same version of the virus that was found in a Louisiana patient suffering from severe illness, and it showed some mutations that researchers say increase the virus’s ability to replicate in human cells .

In the Louisiana case, CDC researchers suspected that the mutations arose during replication in the patient and were unlikely to exist in the wild.

Regardless of where and when they occurred, said Jennifer Nuzzo, director of the Pandemic Center at Brown University in Providence, Rhode Island, “it is concerning because it indicates that the virus is changing in a person and may have more severe symptoms than that.” can originally cause infection.”

Furthermore, says Nuzzo, who was not involved in the research, while there is evidence that these mutations occurred after patients were infected and therefore did not circulate in the environment, “it raises the concern that some people will experience a more severe infection.” could than others. “The bottom line is that it’s not a good virus to get.”