Two people, in Wyoming and Ohio, have been hospitalized with H5N1 bird flu, the US Centers for Disease Control and Prevention (CDC) said in a routine flu update on Friday.
The person from Wyoming is still in hospital, while the Ohio patient has been released, according to the report. Both patients experienced “respiratory and non-respiratory symptoms”, the report said, without detailing those symptoms.
“This shows that H5N1 can be very severe and we should not assume that it will always be mild,” said Angela Rasmussen, a virologist at the Vaccine and Infectious Disease Organization at the University of Saskatchewan.
The news comes amid one of the worst seasonal flu outbreaks in 15 years – raising the potential for the emergence of a more dangerous virus that combines bird flu and seasonal flu in a process called reassortment.
“I am very worried about H5N1 in patients that are being treated in hospitals where there are also many seasonal flu patients because this creates opportunities for reassortment, which could potentially produce a pandemic-capable H5N1,” Rasmussen said.
These are the first human H5 cases detected in Wyoming and Ohio.
An “older” woman from Platte county, Wyoming, was hospitalized in another state, according to a statement from the Wyoming department of health. She “has health conditions that can make people more vulnerable to illness”, the statement says.
The woman was exposed to poultry in a backyard flock that tested positive for H5N1, the CDC report said, adding that she remained hospitalized at the time of the report.
A man in Mercer county, Ohio, was infected while depopulating, or killing, H5N1-positive poultry at a commercial facility, according to a statement from the Ohio department of health.
The man has been discharged from the hospital “and is now recovering at home”, the CDC report said.
So far, there have been 70 confirmed cases of the highly pathogenic avian influenza in the US since it was first detected in cows last year.
There is no evidence of human-to-human transmission at this point. The majority of cases have been among people who have close contact with animals.
Previously, a patient in Missouri was hospitalized and tested positive for bird flu after no known exposure. And a man in Louisiana was hospitalized and died after exposure to backyard chickens and wild birds.
A 13-year-old girl was also extremely ill and in the hospital for months in British Columbia after no known exposure.
The Louisiana and BC cases were both caused by a variant of H5N1 that emerged in the fall and has quickly become dominant in birds – and has now spilled over, separately, into dairy cows in Nevada and Arizona.
The new spillovers come as the Trump administration weighs a strategy that wouldn’t seek to contain outbreaks in poultry through depopulation.
The new head of health agencies, Robert F Kennedy Jr, has reportedly stopped a seasonal flu vaccine campaign. A scheduled meeting of the CDC’s independent vaccines committee has also been postponed.
A new study, published by the CDC’s Emerging Infectious Diseases journal, offers some insight into why some cases may not be as severe as others.
Researchers infected ferrets with H1N1 and then, three months later, infected them with H5N1 or H7N9, a low-pathogenicity variant.
H1N1 was the swine flu responsible for the 2009-10 epidemic. It never went away – in fact, it’s one of two seasonal variants behind this year’s flu season.
The ferrets with recent H1N1 antibodies were able to neutralize H5N1 more quickly than H7N9, indicating some protectiveness from the previous infection.
Another new study in the same journal found that ferrets first infected with H1N1 had less severe disease from H5N1 – suggesting that some humans may experience the same, the authors wrote.
“This is evidence that prior H1N1 infection or vaccination may provide some level of cross-protection via anti-N1 immunity,” Rasmussen said.
But it’s not clear to what degree that protection might help people.
“We shouldn’t interpret this to mean protection will be absolute in the human population,” Rasmussen said.
