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Bird flu mutations raise red flags. Northeastern expert warns of increasing human adaptation
In an indication that the bird flu outbreak is “headed in the wrong direction,” sequencing of the virus that has stricken a Canadian teenager shows mutations that could make the infection more transmissible from person to person, says Northeastern expert Samuel Scarpino.
The biggest concern at the moment is that the genome sequence just made available from the Canadian patient indicates “the virus is carrying some concerning mutational signatures suggesting possible adaptation to human infection,” he says.
“The situation is clearly getting worse and not better,” says Scarpino, director of AI + life sciences at Northeastern’s Institute for Experiential AI.
“We’re seeing that this virus has more than enough potential to evolve,” he says.
Scarpino says widespread wastewater testing is needed to track the virus that is widespread in birds and the cause of a multi-state outbreak in dairy cows as well as sporadic outbreaks in poultry flocks.
In the U.S., the 53 human cases of avian flu reported by the Centers for Disease Control and Prevention have been mild for the most part.
But the teenager in British Columbia was reported to be hospitalized in critical condition with respiratory distress after contracting bird flu from an as-yet unknown source.
“It’s concerning because teenagers are not normally hospitalized for influenza,” Scarpino says.
He says preliminary sequencing of the H5N1 variant sickening the teenager showed potential mutations in a protein on the surface of the virus called hemagglutinin.
Mutations to the protein are known to make people more susceptible to the bird flu, Scarpino says. “These two mutations are in red flag parts of the genome now.”
Canadian health officials have ruled out dairy cows as a possible source of transmission and are still investigating how the teen became the first domestically acquired case of H5N1 in Canada.
Scarpino says it’s possible but not likely that there was an error with the preliminary results of genomic sequencing of the virus.
“What’s probably going on is that this person was infected with a virus that came from birds, and (the virus) has evolved within that person to replicate more efficiently in humans,” Scarpino says, adding that viruses have been known to mutate to resist antiviral treatment.
“We’re seeing this evolution in real time now.”
Scarpino says the opportunity for the teen to transmit the virus to another person is likely low because the hospital treating the teen most certainly has infection control protocols in place.
“It’s not like on day one of the infection they were walking around with the human-adapted virus,” he says. “It doesn’t look like it was human-to-human transmission.”
“We probably got lucky this time because the individual likely did not transmit to anyone,” Scarpino says.
The spread of the virus among dairy farms in more than a dozen states, poultry in 48 states, cats and even a pig farm in Oregon is a concern, Scarpino says.
“One qualitative sign that we look for when an outbreak is heading in the wrong direction is that the level of complexity associated with the events goes up,” as is currently the case with multiple outbreaks across the U.S., Scarpino says.
Pigs are of particular concern because they are “sort of an evolutionary laboratory for host switching” due to way their cells are aligned in the upper and lower respiratory tracts, he says. “We never like to see pigs getting infected.”
Many human cases of avian flu have probably been missed, says Scarpino, who would like to see more widespread and rigorous testing of wastewater to get a better understanding of the spread of H5N1.
While avian flu has killed 53% of infected people in other parts of the world, the CDC says the current outbreak in the U.S. poses a low risk to the public.
“The big take home message is the more people that get infected, the more opportunities there are for evolution to do what evolution does, which is increase (chances of) viral replication in humans,” Scarpino says. “It’s just a numbers game.”