Four egg farm workers in Washington state have tested "presumptively positive" for bird flu.
This suspected outbreak in Franklin County marks the first time the highly pathogenic avian influenza H5N1 has been detected in humans in Washington. It is now the sixth U.S. state where humans have tested positive for this highly infectious strain of the virus.
Around 800,000 chickens at the same farm were euthanized after the Washington State Department of Agriculture found they had been infected by an outbreak of avian influenza on October 15.
Workers at the farm were subsequently tested, leading to four testing "presumptively positive" for the virus, the Washington State Department of Health said.
"Washington has monitored the spread of H5N1 closely since it was first detected in poultry in the state in 2022, and our state is prepared with the knowledge, relationships, and tools to minimize its impacts on our community," Washington Secretary of Health Umair Shah said in a Washington State Health Department statement.
What Is H5N1 Bird Flu?
Bird flu, also known as avian influenza, refers to influenza viruses that primarily infect birds but can sometimes spread to other animals, including humans. There are many subtypes, but the most well-known strain that affects humans is H5N1.
Bird flu viruses are divided into two categories: low pathogenic avian influenza (LPAI) and highly pathogenic avian influenza (HPAI). H5N1 is an HPAI that causes severe illness and a high mortality rate in birds.
"Avian influenza A(H7N9) virus and highly pathogenic avian influenza (HPAI) A(H5N1) and A(H5N6) viruses have been responsible for most human illness from avian influenza viruses reported worldwide to date, including the most serious illnesses with high mortality," the CDC explains.
There has been a notable outbreak of H5N1 bird flu in wild birds around the world in recent months. Over 100 million domestic birds across 48 U.S. states and dairy cows across 14 states have also been affected.
"H5N1 highly pathogenic avian influenza (HPAI) has caused ongoing multistate outbreaks in poultry, dairy cattle, and wildlife," the Washington State Department of Health said.
"Avian influenza is a disease caused by avian influenza Type A viruses that naturally occur in wild aquatic birds throughout the world. H5N1 viruses can also infect other species of birds, and occasionally mammals, and can cause significant mortality in poultry species, such as chickens, turkeys, pheasants, quail, ducks, geese, or guinea fowl."
How Many People Have Caught H5N1?
Human cases of H5N1 are rare but can occur through close contact with infected birds or surfaces contaminated by the virus. It does not easily spread from person to person.
"On rare occasions, avian influenza viruses infect people and make them sick. Most instances of people becoming infected with avian influenza have happened after prolonged, close contact with animals infected with avian influenza or environments contaminated with avian influenza," the Washington State Department of Health said.
Before the Washington farm workers, the CDC reported 27 cases of H5N1 bird flu in humans in the U.S. this year, 16 of which have been confirmed as H5N1.
Thirteen of these cases were reported in California, 10 in Colorado, two in Michigan, and one each in Missouri and Texas. One additional case was previously detected in a poultry worker in Colorado in 2022.
"CDC believes the current risk to the general public from bird flu viruses is low," the CDC said. "The spread of bird flu viruses from one infected person to a close contact is very rare, and when it has happened, it has not led to continued spread among people."
Symptoms of Bird Flu in Humans
Bird flu symptoms in humans include typical flu-like symptoms, such as conjunctivitis, fever, cough, sore throat, runny nose, muscle aches, headaches and fatigue.
In some cases, infection may lead to more severe conditions such as pneumonia, multi-organ failure, and even death. H5N1 bird flu has previously been found to have a mortality rate of around 50 percent in humans.
The Franklin County farm workers were found to have only mild symptoms and have been treated with antiviral medication.
"Testing of additional individuals on the farm is currently pending and the number of cases under investigation may change," the Washington State Department of Health said.
"[Washington State Department of Health] and [Benton-Frankin Health District] have provided personal protective equipment to workers on the farm, are monitoring exposed workers for symptoms of avian influenza, and are providing testing, vaccines, and treatment for symptomatic workers."
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