The first bird flu death in the United States is a dire warning

Nuzzo says it’s very possible that the Louisiana patient’s pre-existing health conditions contributed to the severity of his illness, but he 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 in an emergency department in British Columbia for a fever and conjunctivitis in both eyes. She was discharged home without treatment and later developed a cough, vomiting and diarrhea. She was readmitted to the emergency department in respiratory distress a few 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 the New England Journal of Medicinethe girl had a history of mild asthma and an elevated body mass index. It is not known how he got the virus.

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

There is another clue that could explain the severity of the Louisiana and British Columbia cases. The virus samples from the two patients showed some similarities. For one, 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.

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

“In the case of the Louisiana infection, we know that person had comorbidities. We know that person was an elderly individual. These are factors that contribute to more severe outcomes already when it comes to respiratory infections,” says Anderson.

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

A CDC report from late December found genetic mutations in the virus taken from the Louisiana patient that may have allowed it to enhance its ability to infect the upper airways of humans. The report says that the observed changes were likely generated by the replication of the virus throughout the patient’s illness rather than transmitted at the time of infection, meaning that the mutations were not present in the birds that the person was exposed.

Write in the New England Journal of MedicineThe team that cared 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 will acquire mutations that will make human transmission more likely.

For now, people who work with birds, poultry or cattle, or who have recreational exposure to them, are at greater risk of getting bird flu. To prevent illness, health officials recommend avoiding direct contact with wild birds and other animals infected or suspected of being infected with avian influenza viruses.