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 due to bird flu in November. Was admitted.
The 13-year-old girl was initially seen at an emergency department in British Columbia due to fever and conjunctivitis in both eyes. He was sent home without treatment and later developed cough, vomiting and diarrhea. A few days later, she returned to the emergency department due to shortness of breath. She was admitted to the pediatric intensive care unit and developed respiratory failure but eventually recovered after treatment. according to a The case report was published in the New England Journal of MedicineThe girl had a history of mild asthma and high body-mass index. It is unknown how she contracted the virus.
“This tells us that we have no idea who is going to have mild disease and who is going to have severe disease, and so we have to 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 Louisiana and British Columbia cases. Some similarities were seen in the virus samples of both the patients. 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. This is different from the B3.13 subtype, which is predominant in dairy cows.
“Right now, the question is, is this a more serious strain than the strain in dairy cattle?” says Benjamin Anderson, assistant professor of environment and global health at the University of Florida. Yet, scientists don't have enough data to know for sure. A handful of poultry farm workers in Washington have 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 the person had other comorbidities. We know that the man was an old man. These are factors that already contribute to more serious outcomes when it comes to respiratory infections,” Anderson says.
In the cases in Louisiana and British Columbia, there is evidence that the virus may have evolved to cause more severe disease in both patients.
A CDC report from late December The virus taken from the Louisiana patient was found to have a genetic mutation that may have allowed it to increase its ability to infect the upper airways of humans. The report said the observed changes were likely generated by replication of the virus during the patient's illness rather than being transmitted at the time of infection, meaning the mutations were not present in birds the individual had come in contact with.
I am writing New England Journal of MedicineThe team caring for the Canadian teenager also described “worrying” 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 tract.
In the past, bird flu has rarely spread from person to person, but scientists are concerned about a scenario where the virus would acquire mutations that would make human transmission more likely.
Currently, people who work with, or have recreational contact with, birds, poultry, or cows are at greater risk of getting bird flu. To prevent disease, health officials recommend avoiding direct contact with wild birds and other animals infected or suspected of being infected with bird flu viruses.