MONDAY, July 22, 2024 (HealthDay News) — Two more cases of bird flu have been reported in Colorado poultry workers, but reassuring research finds the virus doesn’t seem to be fueling silent infections, U.S. health officials report.

The two additional H5N1 avian flu infections bring the total in that state to six, the U.S. Centers for Disease Control and Prevention said in a health advisory posted Friday.

“Since April 2024, 10 human cases of avian influenza A[H5] infection have been reported in the United States. Four of these cases were associated with exposure to sick dairy cows and six were associated with exposure to H5N1-infected poultry,” the CDC stated. “This includes two additional cases in Colorado that were confirmed by CDC this week and not previously reported. The two new cases were in poultry workers with exposure to infected poultry during depopulation and disposal activities. Similar to previous cases, illness was mild.”

Along with the new cases, the agency offered up some good news: Last month, the Michigan Department of Health and Human Services launched a study of 35 workers who were around cows sickened by the bird flu.

One question that researchers wanted to tackle was if there were people who never had symptoms but showed evidence of past infections. However, none of the blood testing showed antibodies that would indicate past infection, the CDC reported.

“This is an important finding because it suggests that asymptomatic infections in people are not occurring and provides support to the current testing approach — i.e., collecting samples from symptomatic people who have been exposed to sick animals,” the agency noted in its advisory.

Since 2020, a bird flu virus has been spreading among mammals — including even alpacas. Earlier this year the virus, known as H5N1, was detected in U.S. dairy cows, and it is now circulating in livestock in multiple states.

The cases reported earlier this year were among dairy farm workers in Michigan, Texas and Colorado.

As of last Friday, the H5N1 virus has been confirmed in 157 dairy cow herds in 13 states. Since April 2024, the U.S. Department of Agriculture has reported bird flu cases in 34 commercial flocks and 16 backyard flocks, for a total of 18.3 million birds affected.

More information

The CDC has more on the bird flu outbreak.

SOURCES: U.S. Centers for Disease Control and Prevention, news release, July 19, 2024

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