The largest supplier of eggs in the United States halted production after chickens at a Texas plant tested positive for the highly contagious bird flu - the latest in a spike of cases across the nation.

Cal-Maine Foods on Tuesday announced chickens at its facility in Parmer County, in the state's southwestern panhandle, tested positive for pathogenic avian influenza (HPAI) resulting in slaughter of nearly 2 million chickens − 1.6 million hens and 337,000 pullets (young hens).

The announcement less than 24 hours after  the Centers for Disease Control reported a person in Texas had been infected with the virus after coming into close contact with dairy cattle and just over a week after sick dairy cattle in Texas and Kansas tested positive for the virus.

The culled Texas chickens represent about 3.6% of the company’s total flock as of Tuesday, the supplier wrote in a news release.

Production at the Texas facility temporarily ceased while the company follows the protocols prescribed by the U.S. Department of Agriculture, the company said.

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Cal-Maine Foods is largest producer of eggs in the nation

Headquartered in Ridgeland, Mississippi, Cal-Maine Foods is the largest producer and distributor of fresh shell eggs in the nation and said it sells most of its eggs in states across the Southwest, Southeast, Midwest and MidAtlantic.

The company said it "remains dedicated to robust biosecurity programs across its locations; however, no farm is immune from HPAI. HPAI is still present in the wild bird population and the extent of possible future outbreaks, with heightened risk during the migration seasons, cannot be predicted."

Cal-Maine Foods said it was working "to secure production from other facilities" to minimize disruption to its customers.

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Person infected with bird flu in Texas

In a separate news alert this week, the Texas Department of State Health Services reported the patient became "ill following contact with cows presumed to be infected with avian influenza" and that their primary symptom was conjunctivitis, also known as pink eye.

The person who tested positive for bird flu in Texas is only the second known human case in the United States, state and federal officials said this week.

Bird flu in dairy cattle in Kansas, Texas

Last week the USDA announced last week HPAI had been found in unpasteurized clinical samples of milk from ill cows at two dairy farms in Kansas and one in Texas, plus a swab from a dairy cow in Texas.

Wild migratory birds are believed to be the source of the infection, the USDA said, and viral testing and epidemiologic efforts remained underway.

What is bird flu? 

Bird flu is a disease caused by a family of flu viruses primarily transmitted among birds.

Avian influenza viruses, according to the CDC and USDA, are classified into two groups: low pathogenic avian influenza (LPAI) (often seen in wild birds) and HPAI, found mostly in domestic poultry. According to the CDC, LPAI viruses cause mild or no disease, and HPAI cause severe disease and high mortality rates in infected birds.

Bird flu has cost the government roughly $660 million and in recent times raised the price of eggs and poultry. At least 58 million birds were slaughtered last year to limit the spread of the virus.

Bird flu spread to humans is low risk, USDA says

The first case of avian influenza in a person in the United States was reported in Colorado in April 2022.

Federal and state health authorities are investigating the outbreaks, and the USDA said the risk to the general public contracting is low as the viruses have only rarely been transmitted from person to person.

"However, people with close contact with affected animals suspected of having avian influenza A have a higher risk of infection," Texas health officials wrote in a news alert earlier this week.

Bird flu symptoms in humans

Human infection with the bird flu can happen during close contact with infected birds or when people touch sick birds or their saliva, mucus and feces, the CDC said. People contract the virus when it gets into a their eyes, nose or mouth, or when it is inhaled.

Those who contract the virus often experience mild illnesses including an eye infection and upper respiratory symptoms or no symptoms at all, while others can develop a severe sometimes fatal disease like pneumonia.

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What are signs of bird flu?

Indications a bird may be infected with avian influenza include:

• Loss of appetite, lethargy
• Sudden death without prior symptoms
• Eyelid swelling
• Twisting of the head and neck
• Purple discoloration to body parts including waddle and legs

Natalie Neysa Alund is a senior reporter for USA TODAY. Reach her at [email protected] and follow her on X @nataliealund.