This colorized electron microscope image released in March by the National Institute of Allergy and Infectious Diseases shows particles of the avian influenza A H5N1 virus (in yellow). According to the CDC, the first serious case of bird flu in a human has been detected during the current outbreak in the United States.

AP/National Institute of Allergy and Infectious Diseases

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AP/National Institute of Allergy and Infectious Diseases

Federal health officials are dealing with the first serious case of bird flu found in a human during the U.S. outbreak.

Louisiana health officials initially reported the infection last weekone person was hospitalized after being exposed to sick and dead birds in backyard flocks.

On Wednesday, the Centers for Disease Control and Prevention shared its findings indicating that the H5N1 virus responsible for the disease belongs to a genetic lineage that circulates in wild birds and poultry – different from the one that spreads in dairy cows and Most infections in agriculture are caused by workers.

In the USA more than 60 people have been infected So far, although some research suggests The official tally could be an undercount.

Diseases associated with dairy cows have largely resulted in mild illness in humans.

The version of the virus in the Louisiana case is the so-called “D1.1 genotype.” It has already occurred in poultry workers in Washington state developed mild symptoms after testing positive in October. However, recently a teenager in British Columbia was hospitalized after contracting the D1.1 strain of the virus.

Canadian health officials have not been able to determine how this person became infected.

The case in southwest Louisiana was discovered during routine flu surveillance and ultimately forwarded to the CDC for confirmation. There is no evidence that the person spread bird flu to others, and the case does not change the CDC’s assessment that the risk to the general public remains low.

Still, the hospitalization is a reminder that bird flu has caused serious illness and death in other countries over the past 20 years, Dr. Demetre Daskalakis of the CDC told reporters during a press briefing on Wednesday.

Daskalakis said his agency is conducting additional sequencing to look for worrisome changes in the virus that could indicate it is evolving to better infect people or cause more severe disease.

Scientists were concerned that the British Columbia case had certain mutations that could cause problems, although more research was needed to understand the exact effects.

Daskalakis referred reporters to Louisiana officials investigating the case for more details about how the person contracted the virus and what symptoms they were experiencing.

As with the Louisiana infection, most cases have been traced to some form of contact with sick animals. Dairy cows contain high viral loads in their milk, which is believed to lead to infections in farm workers. Anyone who works with infected poultry can also become infected with the virus.

However, several cases have occurred in the United States that cannot be traced back to infected livestock, including in California and Missouri.

“Infections occur without a clear source of exposure. Neither these cases nor the cases with known exposure to animals or animal products have resulted in human-to-human transmission,” Daskalakis said.