What to Know: Another Bird Flu Strain

February 11, 2025

Public health officials are monitoring recent reports of a new strain of the avian influenza that has been recently detected in dairy herds for the first time.

Here’s what you need to know:

• What to know:  Public health officials in Nevada discovered the new strain of the bird flu—D1.1—that is different than the B3.13 type that’s responsible for most dairy herd infections nationwide. The new strain was initially identified via the USDA’s National Milk Testing Strategy.
  • The second strain means that another type has spilled over from wild birds to cattle, highlighting the importance of public health monitoring and precautions. The strain also was detected in a Nevada dairy worker, who has since recovered.
  • Public health leaders monitor mutations to better understand the spread of the disease and the possibility for changes that would enable human-to-human transmission.
• Risk factors:  The health risk to the public remains low, but “people who work with birds, poultry or cows, or have recreational exposure to them, are at higher risk,” Nevada public health officials noted.
• Effective prevention:  Avoiding sources of exposure is key. This means avoiding direct contact with wild birds and other animals infected with or suspected to be infected with bird flu viruses.
• By the numbers:  There have been 68 confirmed total reported human cases in the United States and one death associated with H5N1 bird flu infection, per CDC reports.
  • Most human cases of bird flu have been mild, the CDC said in a recent update, and most stem from known exposure to sick or infected animals.
• The bottom line:  “CDC influenza (flu) surveillance systems show no indicators of unusual influenza activity in people, including avian influenza A (H5N1),” the CDC said in a statement.

Additional information from the CDC is available online.