Updates on the bird flu outbreak, now linked to raw milk products in California

(NEW YORK) — Public health officials are continuing to monitor an outbreak of avian influenza, also known as bird flu, as it spreads across the U.S.

The strain, known as H5N1, sickened several mammals this year before infecting dozens of Americans, according to the Centers for Disease Control and Prevention.

There is no evidence of person-to-person transmission of bird flu, and the risk to the general public is low, the CDC said.

But public health experts have also said it’s important to be alert during the respiratory virus season and to be aware of risks that could come from exposure to infected animals and from drinking raw milk.

Here’s the latest information on the outbreak in the United States:

What is the status of the bird flu outbreak?
Avian influenza, or bird flu, is an infectious viral disease that primarily spreads among birds and is caused by infection with Avian Influenza A viruses.

These viruses typically spread among wild aquatic birds but can infect domestic poultry and other bird and animal species, according to the CDC. In the U.S., the virus infected dairy cows.

“What’s made this year’s outbreak interesting is the association with dairy cows, which is not an association that’s been seen before,” Michael Ben-Aderet, an infectious disease physician and associate director of hospital epidemiology at Cedars-Sinai Medical Center in Los Angeles, told ABC News.

“H5N1 has been known for many, many years. It’s not a new strain of bird flu, but we haven’t seen it cross over into dairy cows and have this association with dairy cows and dairy workers,” he continued.

As of Thursday, 58 human cases have been confirmed in seven states, according to CDC data. California has the highest number of cases with 32.

Almost all confirmed cases have had direct contact with infected cattle or infected livestock.

So far, all bird flu cases in the U.S. have been mild, and patients have all recovered after receiving antiviral medication.

“There has been another strain in Canada that caused really severe disease in a teenager who ended up in critical condition in the hospital,” Dr. Meghan Davis, an associate professor of environmental health and engineering at Johns Hopkins Bloomberg School of Public Health, told ABC News. “So yes, these [strains] are highly related, but not quite the same.”

What are the risks associated with raw milk?
In April reports emerged of bird flu fragments found in samples of pasteurized milk.

However, the fragments are inactive remnants of the virus; they cannot cause infection because the commercial milk supply undergoes pasteurization.

“The good news is that pasteurization inactivates [the virus], and so, when you do that test to look at fragments of the virus, although we find it in milk, the pasteurization process ensures that live virus is not transmitted,” Albert Ko, an epidemiologist at the Yale School of Public Health, told ABC News.

However, the Food and Drug Administration has previously warned of the possible dangers associated with drinking raw, unpasteurized milk due to elevated risks of foodborne illness.

On Tuesday, all of Raw Farm’s raw whole milk and cream products that were still on store shelves in California were being voluntarily recalled by the company, following multiple detections of bird flu virus in its milk and dairy supply within the past week, according to public health officials.

The CDC said it considers exposure to raw milk without personal protective equipment a “high-risk exposure event.”

“Raw milk consumers need to be aware that even handling the product itself could be a kind of exposure,” Davis said. “So, if you’re pouring it, you spill a little milk, get that on your hands, touch your eyes. You could get the same kind of exposure as someone who works in a dairy farm.”

Are we at risk of a bird flu pandemic?
Experts said the U.S. is currently not experiencing a bird flu pandemic, nor is the country presently at risk of a bird flu pandemic.

However, they said with each new human case, it offers a chance for the virus to mutate, theoretically enabling human-to-human transmission to occur at a point in the future.

“I think the warning sign is just, because there’s so much transmission in birds and there’s transmission now in our cattle, particularly we really are concerned about the possibility that there may be a mutation that enables person to person or human-to-human transmission,” Ko said.

Ben-Aderet said there is also concern as the U.S. heads into the winter respiratory virus season that the seasonal flu — which has the ability to exchange parts of its genome with other influenza viruses — could do the same with bird flu.

Health officials are taking proactive measures to prevent such a situation from occurring.

The World Health Organization announced in July that it has launched an initiative to help accelerate the development of a human bird flu vaccine using messenger RNA technology.

In October, federal health officials announced they are providing $72 million to vaccine manufacturers to help ensure available non-mRNA bird flu vaccines are ready-to-use, if needed.

There are currently no recommendations for anyone in the U.S. to be vaccinated against bird flu.

ABC News’ Youri Bendjaoud contributed to this report.

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