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

Nuzzo says it’s very likely that the Louisiana patient’s prior 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 a British Columbia emergency department for fever and conjunctivitis in both eyes. She was discharged home without treatment and later developed coughing, vomiting and diarrhea. She ended up back in the emergency department due to respiratory distress a few days later. She was admitted to the pediatric intensive care unit and developed 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 a high body mass index. It is not known how she contracted the virus.

“What that tells us is that we have no idea who is going to get mild disease and who is going to get severe disease, which is why we have to take these infections seriously,” Nuzzo says. “We should not assume that all future infections will be mild.”

There is other evidence that could explain the seriousness of the Louisiana and British Columbia cases. Virus samples from both patients showed some similarities. First, they were both infected with the same subtype of H5N1 virus called D1.1, the same type of virus found in wild birds and poultry. It is different from subtype B3.13, which is prevalent in dairy cows.

“The question now is: Is this a more dangerous breed than dairy cows?” 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 small number of poultry farm 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 comorbidities. We know this person was an older individual. “These are factors that contribute to actually more serious outcomes when it comes to respiratory infections,” Anderson says.

In the cases of Louisiana and British Columbia, there is evidence that the virus may have evolved in both patients to lead to more serious illness.

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

Write in New England Journal of MedicineThe team that cared for the Canadian teen also described “alarming” mutations found in her viral samples. These changes could have allowed the virus to more easily attach to and enter cells in the human respiratory system.

In the past, bird flu was rarely transmitted from person to person, but scientists are concerned about a scenario in which the virus acquires mutations that would make human-to-human transmission more likely.

Currently, people who work with birds, poultry, or cattle, or who are exposed to them recreationally, are at greater 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 avian influenza viruses.