Second bird flu case confirmed in human in US: What to know

Federal authorities are downplaying the public health risk after the second ever case of a human contracting the “highly pathogenic” bird flu in the United States was confirmed in Texas on Monday. 

The infected man was exposed while he worked as a dairy worker, the Texas Department of State Health Services said. The person had minor symptoms but has received treatment, state health officials said.

“This infection does not change the H5N1 bird flu human health risk assessment for the U.S. general public, which CDC considers to be low,” the Centers for Disease Control and Prevention (CDC) said in a statement on Monday. 

The CDC added that people with “close or prolonged, unprotected exposures to infected birds or other animals (including livestock), or to environments contaminated by infected birds or other animals” are at greater risk of infection.

USDA has confirmed infections of dairy cattle herds in five states — Texas, Kansas, Michigan, New Mexico — with results in Idaho “presumed” to be positive.

The movement of cattle across state lines, especially from Texas, has accounted for the spread, according to CDC. States like Nebraska have issued temporary restrictions on cattle imports because of the bird flu. 

Here’s what to know.

Worst outbreak in U.S. history among animals

Bird flu, also known as H5N1 or avian influenza, has ravaged billions of dollars of poultry across the world, but mass infections of cattle — and human infections — are rare.

The avian flu’s modern history in humans begins in China in 1996, where it spread from geese to people in Hong Kong the following year. In a two month period, it killed a third of the 18 people it infected, according to the CDC.

The Hong Kong outbreak showed for the first time that the virus could transmit from birds to humans directly. Direct, prolonged contact with or consumption of infected birds has often explained avian flu transmission in the nearly three decades since.

However, cases of humans contracting the disease since have been sporadic and isolated. The worst fear among public health experts is human-to-human transmission of the virus, which has yet to occur.

Still, the virus has killed more than 50 percent of its human victims from 2003 to 2016, according to a study published by the National Institute of Health (NIH). 

Second-ever human infection in US

The infection of the Texan dairy worker is the second–ever infection in the U.S., but the first contracted from cattle.

In 2022, a Colorado prisoner, participating in a work program at a poultry facility, contracted the virus after killing infected birds. 

Neither the Texas dairy worker nor the Colorado prisoner experienced serious symptoms, and both have recovered after treatment, according to the CDC.

Record outbreak among poultry

In the U.S, the highly pathogenic avian influenza (HPAI) has spread to affect 82 million birds in 48 states, resulting in massive culls of commercial poultry and billions of dollars in losses — the worst outbreak of bird flu in U.S. history, according to the USDA. 

Just a day after the dairy worker infection, Cal-Maine Foods, a major poultry producer, was ordered to “depopulate” nearly 2 million chickens after a positive test for HPAI at their facility in Farwell, Texas.

Sid Miller, commissioner of the Texas Department of Agriculture, ordered the plant’s temporary closure and called on producers to act.

“Given this latest development, all producers must practice heightened biosecurity measures. The rapid spread of this virus means we must act quickly,” he said. 

Because the virus is an influenza variant with a “natural reservoir” in wild aquatic birds, it is impossible to eradicate and zoonotic infections will continue, according to the World Health Organization (WHO). 

The CDC has labeled the risk to the public “low” after finding no mutations for human transmission, and has said commercial products like milk, eggs and poultry remain safe.

The spread of avian influenza has public health officials on guard. 

WHO has called for extensive monitoring of all cases of HPAI, animal or human, for signs that it may be mutating to threaten humans.

“The emergence of an influenza A virus with the ability to infect people and sustain human-to-human transmission could cause an influenza pandemic,” WHO said. “[The] human population has little to no immunity against the virus,” it added. 

The CDC has recommended people practice good hygiene, avoid sick or dead animals, animal fecal matter and consumption of untreated or uncooked animal products like raw milk or raw eggs.