Bird flu: New strain detected in US dairy worker, health officials say

A dairy worker in the US state of Nevada was infected with a new type of bird flu that is different from the version that has been spreading in US cattle since last year, US health officials said.

The person was not hospitalised and has recovered from their mild illness, according to the US Centers for Disease Control and Prevention (CDC).

Their main system was eye redness and irritation, similar to most bird flu cases associated with dairy cows.

The newer strain had been seen before in more than a dozen people exposed to poultry, but this is the first time an infection was traced to a cow.

CDC officials said there is no evidence the virus has spread from this person to any other people. The agency continues to say the virus poses a low risk to the general public.

The bird flu currently spreading through animals, and some people, is known to scientists as Type A H5N1 influenza.

The US outbreak has international health authorities on edge because of the potential for the virus to mutate to a point where it becomes more transmissible among people, which could lead to a flu pandemic.

Avian influenza cases have been rising among wild birds worldwide, and a person in the UK was infected last month.

But there are different strains. In the US, a version known as B3.13 was confirmed last March after spreading to cattle in late 2023. It has infected 962 cattle herds in 16 states, mostly in California.

The newer version, known as D1.1, was confirmed in Nevada cattle in late January after being found in milk collected as part of a monitoring program started in December.

Two types of avian influenza

That discovery of D1.1 meant distinct forms of the virus have spread from wild birds into cattle at least twice.

Experts said it raises questions about wider spread and the difficulty of controlling infections in animals and the people who work with them.

At least 68 people in the US have been reported infected with bird flu in the last year, according to CDC data.

All but a small handful worked closely with cows or poultry, and most caught the B3.12 version.

The CDC previously said the D1.1 version had been seen only in cases in Louisiana and Washington state.

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But on Monday, the agency revealed that available data indicates D1.1 last year likely infected a total of 15 people in five states – Iowa, Louisiana, Oregon, Washington, and Wisconsin – all related to poultry.

The D1.1 version of the virus was linked to the first US death tied to bird flu and to a severe illness in Canada.

A person in Louisiana died in January after developing severe respiratory symptoms following contact with wild and backyard birds. In British Columbia, a teen girl was hospitalised for months with a virus traced to poultry.

While the risk to the general public is low in the US, the CDC says bird flu poses a greater threat to people with close or prolonged contact with infected cows, birds, or other animals.

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