A 3-year-old girl in Mexico died this month after getting infected with H5N1 bird flu, according to a report issued by the World Health Organization this week.
Authorities say the strain of bird flu is one that has been circulating in wild birds throughout North America, known as D1.1. It is the same strain implicated in the death of a person in Louisiana earlier this year, and in the case of a 13-year-old Canadian who was placed on life-support for several weeks before recovering.
Two others, a person in Wyoming and a poultry worker in Ohio, were also reported to have severe disease after exposure to this strain of the virus.
The strain has been detected in dairy herds from Nevada and Arizona.
“The case in Mexico is another great reminder of how dangerous H5 viruses can be,” said Richard Webby, an infectious disease expert at St. Jude Children’s Research Hospital in Memphis, Tenn.
The D1.1 strain is widespread in the U.S. and Canada, but until this week’s WHO report it was unclear how far south the strain had traveled, he said.
“It has been a very active virus to date,” he said, and “further spread will undoubtedly lead to more infections, both in birds and humans. “
He said researchers are now awaiting publication of the genetic sequence, which will provide more information about whether there have been further changes that could make it more severe and/or transmissible.
According to the WHO, the young girl’s symptoms, which included fever, malaise and vomiting, began on March 7. She was admitted to a hospital in the state of Durango on March 13 due to respiratory failure. She was treated with oseltamivir, an antiviral drug, the following day. On March 16, she transferred to another hospital in the city of Torreón.
She died on April 8 from “respiratory complications.”
The girl did not have any underlying medical conditions, had not received a seasonal influenza vaccination, and had no history of travel, according to the WHO report.
The source of the child’s infection remains under investigation.
According to the report, 91 people were identified as contacts of the toddler, including 21 household contacts, 60 healthcare workers and 10 people from a childcare center. Each of these people was tested and all have tested negative for the virus.
Between 2022 and August 2024, there have been 75 reported H5N1 poultry outbreaks across Mexico, although none in Durango. At the end of January 2025, a sick vulture at the Sahuatoba Zoo, in Durango, was diagnosed with the virus. In addition, dozens of wild birds in the state were also reported, including a Canada goose.
The virus is still circulating in U.S. dairy herds, poultry, wild birds and wild mammals. Since April 1, there have been five new reports of infected dairy herds from California, 15 in Idaho and one from Arizona, according to the US Department of Agriculture.
There have also been dozens of domestic cats infected with the virus, including three recent reports from California’s Orange and Alameda counties: two in Orange and one in Alameda.
According to the U.S. Centers for Disease Control and Prevention, there have been 70 reported cases of H5N1 bird flu in the U.S. since March 2024, when the virus was first reported in dairy herds. There has been one death, a person older than 65 from Louisiana.
Health officials say the risk of H5N1 bird flu to the general public remains low and there has been no indication of person-to-person spread. Most cases have been associated with contact with infected livestock and poultry.