Nuzzo said it's likely the Louisiana patient's pre-existing health conditions contributed to their illness, but also pointed to the case of a teenager in Canada who was hospitalized with bird flu in September. 11.
The 13-year-old girl was initially taken to an emergency department in British Columbia for fever and conjunctivitis in both eyes. She was discharged home without treatment and subsequently developed cough, vomiting and diarrhea. She returned to the emergency room in respiratory distress a few days later. The girl was admitted to the pediatric intensive care unit and suffered respiratory failure but eventually recovered after treatment. According to one 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 unknown how she contracted the virus.
“What that tells us is we don't know who's going to get mild disease and who's going to get severe disease, and so we have to take these infections very seriously,” Nuzzo said. “We should not assume that all future infections will be mild.”
There is another clue that could explain the severity of the cases in Louisiana and British Columbia. Virus samples from both patients showed some similarities. First, both were infected with the same H5N1 virus called D1.1, the same virus found in wild birds and poultry. It is different from subtype B3.13 which predominates in dairy cattle.
“Right now, the question is, is this a more serious strain than the dairy strain?” said 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. Some poultry farm workers in Washington have tested positive for subtype D1.1, but those people had mild symptoms and did not require hospitalization.
“In the case of the infection in Louisiana, we know the person had comorbidities. We know that person is an elderly individual. These are factors that contribute to more serious outcomes when it comes to respiratory infections,” Anderson said.
In the cases in Louisiana and British Columbia, there is evidence that the virus may have evolved in both patients to cause more severe illness.
ONE CDC report from late December found a genetic mutation in the virus taken from the Louisiana patient that may have allowed it to increase its ability to infect the human upper respiratory tract. The report said the observed changes were likely caused by virus replication during the course of the patient's illness rather than transmission at the time of infection, meaning the mutations were not present. appears in birds that the person comes into contact with.
Write in New England Journal of MedicineThe team caring for the young Canadian girl also described “worrying” mutations found in her virus samples. These changes may allow the virus to more easily bind to and enter cells in the human respiratory tract.
Previously, bird flu was rarely transmitted from person to person, but scientists are worried about a scenario where the virus will have mutations that make it more likely to be transmitted to humans.
Currently, people who work with birds, poultry or cows or come into contact with them recreationally are at higher risk of contracting avian influenza. To prevent illness, health officials recommend avoiding direct contact with wild birds and other animals infected or suspected of being infected with avian influenza virus.