A Michigan dairy worker has tested positive for highly pathogenic avian influenza associated with the multistate outbreak of avian flu in dairy cattle.

The federal Centers for Disease Control and the Michigan Department of Health and Human Services announced the human case on Wednesday. CDC said the dairy worker, who was being monitored because of exposure to H5N1-infected cattle, reported symptoms to local health officials.

A Texas farmworker, who also worked on a dairy farm where H5N1 had been identified, was diagnosed earlier this spring. While a nasal swab from the Michigan farmworker tested negative, an eye swab was shipped to CDC and tested positive for the virus, according to CDC.

Public risk

CDC has been monitoring influenza surveillance systems closely, particularly in the affected states, and there has been no sign of unusual influenza activity in people, the agency reported.

“Based on the information available, this infection does not change CDC’s current H5N1 bird flu human health risk assessment for the U.S. general population, which the agency considers to be low.

Only one other human case has been diagnosed in the U.S. It was in Colorado in 2022.

As of May 22, USDA’s Animal and Plant Inspection Service reports 52 cases of H5N1 on dairies in nine states, with the latest cases detected in Texas on May 20 and in Michigan and Idaho on May 16.

The number of affected dairies in those states include:

• Michigan 15.

• Texas 14.

• New Mexico 8.

• Idaho 6.

• Kansas 4.

• Colorado 2.

• South Dakota 1.

• North Carolina 1.

• Ohio 1.

Food safety

On April 25, the Food and Drug Administration reported the initial result of a study of 297 retail samples of dairy products found inactive particles of the virus in pasteurized commercial milk.

In a May 10 update, the agency announced that all 297 samples of retail dairy products were found to be negative for viable H5N1 virus.

Those samples were collected at retail locations in 17 states, representing products produced at 132 processing locations in 38 states. The agency tested milk, cream, half-and-half, cottage cheese, sour cream and yogurt.

In addition to FDA’s efforts, USDA is conducting three studies on the safety of beef in regard to the virus.

On May 1, USDA reported all 30 samples of retail ground beef from states with positive infected dairies tested negative for the H5N1 virus.

On May 16, USDA reported in its cooking study of ground beef patties inoculated with a high concentration of the virus, no virus remained in burgers cooked to 145 degrees and 160 degrees.

A final study will analyze samples of muscle meat of cull dairy cows condemned at select inspected slaughter facilities. On April 26, FDA reported it found no viral fragments or virus in infant formula products.

Symptoms

Reported signs and symptoms of bird flu virus infections in humans have ranged from no symptoms or mild illness, such as eye redness or mild flu-like upper respiratory symptoms, to severe — such as pneumonia requiring hospitalization.

Severe symptoms included fever or feeling feverish, cough, sore throat, runny or stuffy nose, muscle or body aches, headaches, fatigue and shortness of breath or difficulty breathing.

Less common signs and symptoms include diarrhea, nausea, vomiting or seizures.

Source: CDC