A new strain of bird flu, designated D1.1, has been detected in U.S. dairy cows for the first time, according to an announcement made by the U.S. Department of Agriculture (USDA) on Wednesday.

Previously, all cases of bird flu in U.S. dairy herds were associated with a different strain known as B3.13.

The emergence of D1.1 in cattle, specifically identified in dairy cows in Nevada, marks a significant spillover event since this strain has primarily been found in wild birds and poultry.

The detection was made as part of the USDA’s national milk testing program, which began in early December.

In their statement, the USDA’s Animal and Plant Health Inspection Service (APHIS) confirmed their collaboration with the Nevada Department of Agriculture to carry out additional investigations and testing on farms.

This effort aims to gather more epidemiological data to better understand the situation and mitigate the spread of the disease.

As of the latest report, there have been 957 confirmed cases of cattle infections across 16 states, with 36 new infections reported in California and Nevada within the last 30 days.

Notably, the D1.1 strain has potential implications for human health. Since April 2024, there have been 67 documented human cases of bird flu in the U.S., including a case involving D1.1 in Louisiana, where the patient unfortunately passed away.

Health officials noted that this individual was over 65 years old and had pre-existing health conditions.

In addition, a 13-year-old girl in British Columbia, Canada, was admitted to intensive care in November with the same strain, highlighting the importance of ongoing monitoring and research into this emerging health concern.