Four agricultural workers in southeast Washington have preliminarily tested positive for bird flu after working around an infected poultry flock at a commercial egg farm.

The cases, if confirmed, would be the first time people in Washington have contracted the virus since officials began tracking a notable rise of it in birds and other animals starting in the U.S. around 2022. Since then, upward of two dozen human cases have been detected across five other states — all but one tied to contact with infected animals.

Health officials emphasized that the four positive cases in Washington are “presumptive,” pending confirmation and analysis by the U.S. Centers for Disease Control and Prevention.

“We are still going through the ongoing investigation,” Dr. Umair Shah, Washington’s secretary of health, said during an online press conference on Sunday.

“At this time, we believe the individuals that we have gotten the results back have been exposed to infected poultry. We do not have evidence at this time of human-to-human spread. However, that is still part of our investigation,” Shah added. 

The Washington farm workers who appear to have the virus have not been hospitalized, according to state and local health officials.

Dr. Steven Krager, the local health officer for Benton and Franklin counties, said the workers had shown signs of mild upper respiratory illness, including runny nose, sore throat, and mild cough, as well as conjunctivitis — often referred to as “pink eye.”

The outbreak at a commercial egg farm in Franklin County involves a flock of about 800,000 birds. It is the first bird flu incident at a commercial poultry farm this year.

Test results on Oct. 15 showed the poultry were infected with bird flu. Testing of people showing symptoms of the virus was arranged on Friday and results indicating that they were positive came back late Saturday, Krager said.

‘Evolving situation’

The type of bird flu that has been circulating in the U.S. is known formally as an H5 highly pathogenic avian influenza. This disease has caused outbreaks across the country in poultry, dairy cows, and various wildlife, including harbor seals in northwest Washington.  

Risks to the general public are considered low, according to the CDC. So far, it’s people who spend time around animals that get the virus who are more likely to catch it. 

But health officials are on alert for indications the disease is changing in a way that could allow for sustained person-to-person spread or more severe illness in humans. A leading concern is that the virus could mutate in ways that allow it to spread easily among people.

Between 2003 and April of this year, the World Health Organization recorded 889 cases and 463 deaths in 23 countries caused by the H5N1 bird flu virus.

“If we were to look at all avian influenza H5 infections reported since 2003, the case fatality rate is quite high, over 50%,” noted Tao Sheng Kwan-Gett, the state Department of Health’s chief science officer.

“We’re not seeing that here. But that is something that would be very worrisome, and so severity of illness is something that we’ll want to monitor closely,” he said.

Shah said that 25 people had been tested so far as part of the response in Franklin County and that 12 tests had come back negative.

“This is an evolving situation,” he said. “There are more individuals that we want to continue to conduct our investigation with and more individuals that we want to potentially test for. And that’s what we are in the process of doing right now.”

The other five states that have had documented bird flu infections in humans include California, Colorado, Michigan, Missouri, and Texas.

Cases across those states, since April, totaled 27, according to CDC figures updated Friday. Of those, a combined 23 were in either California or Colorado. Nationwide, 16 cases are confirmed to have been the H5N1 version of the virus.

A single human case in Missouri is the only one that the CDC data doesn’t connect to exposure to infected poultry or cattle.

‘Not unexpected’

Bird flu can decimate poultry flocks, rapidly causing severe illness and death for fowl.

Fall is a risky time of year for the disease in Washington because it is relatively common among migratory wild birds. Wild birds that travel north from the lower 48 states in summer mingle with other birds from Asia and Europe — a ripe opportunity for bird flu to spread and evolve.

“We all kind of hold our breath and wait for them to come back down and see what kind of reassortment they’ve brought with them,” said the state veterinarian, Amber Itle. “This was not unexpected that we would see some additional detections of the avian influenza virus again this fall. But we were sure hoping that it would be a less pathogenic strain.”

Since 2022, Washington has seen avian influenza in 47 flocks of poultry. Two of them were commercial, including the Franklin County outbreak, and the rest were domestic. The other commercial flock was about 1 million birds. The domestic flocks varied widely in size.

Itle said the state and agricultural operations are monitoring for bird flu at other poultry and dairy farms in the vicinity of the one where the latest bird flu outbreak occurred. She declined to provide specifics on the number of farms in the immediate area, but said there are no signs currently that the virus has spread to dairy cattle. 

“This detection that we have is a poultry strain, it is not a dairy strain,” Itle said. “We’ve had no detections in dairies in Washington state.”

The birds at the Franklin County farm where the outbreak occurred were almost all euthanized by Sunday, Itle said. She said that eggs from the site would be destroyed as well.

“Your eggs are safe and your poultry is safe,” she said. “No birds that are infected or have been infected are entering the food chain. They’re all being disposed of, and will be undergoing composting that can deactivate this virus.”

The U.S. Department of Agriculture has a program to compensate farmers for losses tied to bird flu. But Itle highlighted that the killing of thousands of birds can be trying for farm owners and workers, especially as risks from the virus are still present on a farm. 

There are recommended personal protective equipment guidelines for sites where the disease is present. And the state has protective gear it can make available upon request.

People with backyard flocks of poultry need to be vigilant as well.

State agriculture officials estimate about 15% of migrating waterfowl are infected with bird flu and can easily contaminate an environment by landing in a pond, entering a coop, or gathering food around bird feeders. 

“The most important thing you can do if you have backyard poultry is to keep your birds in and away from wild waterfowl,” Itle said. “It’s really, really important because we need to protect your birds. But also we need to protect you.”