The case of a Canadian woman who died of H5N1 bird flu earlier this month has mystified flu experts, who say they are both puzzled by how she got the virus, and more than a little surprised that it was H5N1 and not a newer virus, called H7N9, that infected her.
The woman’s unusual symptoms – she didn’t have some of the more obvious signs of flu – prompted a health alert from the U.S. Centers for Disease Control and Prevention this week reminding doctors to be on the lookout for odd symptoms.
“It caught us a little unawares because we were expecting this to happen with H7N9,” CDC flu expert Marc-Alain Widdowson told NBC News. “It came a little out of the blue.”
The victim, a 22-year-old nurse from the central Canadian province of Alberta, had encephalitis – a swelling of the tissue surrounding the brain. She also had pneumonia, but her flu infection wasn’t diagnosed right away and she apparently wasn’t coughing hard.
By the time she came back to the hospital a few days later, she was already dying. Severe and unusual symptoms are a hallmark of avian influenzas, doctors say.
The CDC says people coming back from countries affected by any kind of avian flu should be on the lookout. “Clinicians should consider the possibility of avian influenza A (H5N1) virus infection in persons exhibiting symptoms of severe respiratory illness who have appropriate travel or exposure history,” the Health Alert reads.
And travelers to affected regions should stay away from live or freshly killed birds and only eat meat or eggs that have been thoroughly cooked.
Since 2003, H5N1 has infected around 650 people in 16 countries – counting the latest case in Canada – and killed around 350 of them, according to the World Health Organization. In most cases, it causes severe pneumonia, acute respiratory distress syndrome, and, eventually, multiple organ failure. But experts say it sometimes causes encephalitis and septic shock.