The teenager hospitalized with bird flu in British Columbia, Canada, may have a variant of the virus that has a mutation that makes it more transmissible among humans, early data shows – a warning about what the virus can do , which is especially concerning in countries like the US, where some H5N1 cases go undetected.
The U.S. definitely isn’t testing and monitoring enough cases of bird flu, which means scientists could miss mutated cases like this, says Richard Webby, a virologist in the infectious diseases department at St Jude Children’s Research Hospital.
“We have to monitor this as closely as possible. Any warning we can get that there are more viruses making these kinds of changes will give us a heads up,” Webby continued.
The Canadian teen first developed symptoms on November 2 and was admitted to British Columbia Children’s Hospital on November 8. The child remains in critical condition and is suffering from acute respiratory distress – a serious lung condition that can be fatal.
Preliminary sequencing of the H5N1 variant that sickened the teen showed a potential mutation at the genomic site known to make people more susceptible to the virus.
That could indicate that H5N1 has the ability to resemble a human virus more than an avian virus, but it’s also not yet clear whether this change is meaningful and more dangerous for humans, experts said.
The virus may have mutated during the course of the teen’s illness; additional sequencing could reveal more about its evolution.
“Often it’s not just one thing that’s going to confer that ability” to infect people more effectively, says Angela Rasmussen, a virologist at the University of Saskatchewan’s Vaccine and Infectious Disease Organization.
“It’s not entirely clear yet what the real-world implications will be, but all these things are certainly a warning sign,” Rasmussen said. “We really need to pay attention to this, and we really need to try to reduce more human infections as much as possible.”
The specific variant of H5N1 circulating among birds in British Columbia and the northwestern U.S. emerged in recent months, several years after bird flu was first found in North America, Webby said. The variant also sickened 11 workers in Washington state who killed infected poultry, although among those workers the possible mutation had not been detected in the teenager.
“It seems to be quite active in terms of infecting animals and infecting people, so I think it’s one to keep an eye on,” Webby said. “It has some unique features that we just have to keep an eye on.”
No new cases have been detected among the Canadian teen’s contacts, which include family, friends and health care workers. The teen’s case was discovered through disease surveillance – the regular investigation of positive flu cases – at the hospital, and no other cases in the area have been discovered through that system.
“We have a strong influenza surveillance in B.C. and have had an increase in testing requests for H5 so far and all negative,” said Bonnie Henry, an epidemiologist, physician and the provincial health officer with British Columbia’s Ministry of Health.
Canadian officials have conducted blood tests among the teen’s contacts and expect results later this week. They are also awaiting the results of other tests conducted this weekend.
Officials are “still hopeful on the exposure side of finding out how the young person was infected, but there’s nothing new to report yet,” Henry said.
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Although there have been outbreaks of H5N1 among poultry in British Columbia, the teen has not been exposed – but he or she has had contact with several pets, including dogs, cats and reptiles.
It’s possible that one of these animals came across a dead bird or animal and passed the virus to the teen, Rasmussen said, adding, “I don’t think people realize how often we can come into contact with wild animals, including birds. ”
Canadian officials have been working to quickly identify these types of cases, Rasmussen said.
“There’s always more monitoring you can do. However, it is not like in the US, where they seem to actively oppose animal and human testing,” Rasmussen said.
“I find it absolutely baffling that they don’t test every animal on a farm after it’s been determined to be infected,” she said. Farm owners and workers are resistant to testing for social, financial and legal reasons, and workers are often left in the dark about outbreaks, putting them at greater risk of becoming ill.
In Canada, experts hope the mutated virus will die out without being passed on to anyone else. “If there are any more human cases, they will also be isolated, and that means that this virus has reached an evolutionary dead end,” Rasmussen said.
But if the mutation happened once, it could happen again — a particular concern among less well-controlled populations, she said.
“If we have human cases that are not detected, that increases the risk that some of these viruses could be passed on, and by the time we do detect them, it may have spread further,” Rasmussen said. “That’s why we have to remain very vigilant here.”
The possibility of a more transmissible virus was a warning sign, Webby said. It “highlights the need for us to do something about this virus. We have to get it under control.”