The first bird flu death in the US is a serious warning

Nuzzo says it’s very possible that the Louisiana patient’s pre-existing health problems contributed to the severity of their illness, but also points to the case of a teenager in Canada who was hospitalized with bird flu in November.

The 13-year-old girl was initially seen at an emergency room in British Columbia for a fever and conjunctivitis in both eyes. She was discharged home without treatment and later developed cough, vomiting, and diarrhea. She returned to the emergency room with respiratory distress several days later. She was admitted to the pediatric intensive care unit and went into respiratory failure, but eventually recovered after treatment. According to a case report published in New England Journal of Medicinethe girl had a history of mild asthma and an elevated body mass index. It is not known how she contracted the virus.

“This tells us that we have no idea who will develop mild disease and who will develop severe disease, and therefore we should take these infections very seriously,” Nuzzo says. “We should not assume that all future infections will be mild.”

There is another clue that may explain the severity of the cases in Louisiana and British Columbia. Viral samples from the two patients showed some similarities. For one thing, both were infected with the same subtype of H5N1, called D1.1, which is the same type of virus found in wild birds and poultry. It is different from subtype B3.13, which is dominant in dairy cows.

“Right now, the question is, is this a more severe strain than the dairy cattle strain?” says Benjamin Anderson, assistant professor of environment and global health at the University of Florida. So far, scientists don’t have enough data to know for sure. Several poultry workers in Washington have tested positive for the D1.1 subtype, but these individuals had mild symptoms and did not require hospitalization.

“In the case of the Louisiana infection, we know that this person had co-morbidities. We know this person was an older person. These are factors that contribute to more severe outcomes when it comes to respiratory infections,” says Anderson.

In the Louisiana and British Columbia cases, there is evidence that the virus may have evolved in both patients to cause more severe disease.

A CDC report from late December have found genetic mutations in the virus taken from a patient in Louisiana that may have allowed it to improve its ability to infect the upper respiratory tract of humans. The report said the observed changes were likely generated by virus replication during the patient’s illness rather than transmitted during infection, meaning the mutations were not present in the birds to which the man was exposed.

Writing in New England Journal of Medicinethe team caring for the Canadian teenager also described “worrying” mutations found in her viral samples. These changes could allow the virus to more easily bind to and enter cells in the human respiratory tract.

In the past, bird flu has rarely been transmitted from person to person, but scientists worry about a scenario where the virus acquires mutations that would make human transmission more likely.

For now, people who work with or have recreational contact with birds, poultry, or cows are at higher risk of contracting bird flu. To prevent illness, health officials recommend avoiding direct contact with wild birds and other animals infected or suspected of being infected with bird flu viruses.