Bird flu outbreak worsens in US

An outbreak of bird flu in the United States is hitting 25 states, killing over 23 million chickens and turkeys in the worst outbreak since 2015. Federal health officials are watching for potential mutations of the virus that could make it more of a threat to humans.

Some birds have died from the disease, but the vast majority are being culled to try to stop the highly infectious virus from spreading. The spread of the disease has largely been blamed on the migration of wild birds flying over domestic flocks and transmitting the virus through their droppings.

The bird flu virus－H5N1－poses only a low risk to humans, according to the Centers for Disease Control and Prevention. No human infections of the highly pathogenic avian influenza, or HPAI, which includes H5N1, have ever been reported in the US.

The virus can spread from birds to people, but such infections are rare and have not led to outbreaks among humans.

"We're concerned with any avian influenza virus that's circulating in domestic poultry or wild birds," Todd Davis, an expert on animal-to-human diseases at the CDC, told National Public Radio.

The only person known to have contracted this particular bird flu virus was an elderly person in the United Kingdom who lived in close contact with ducks. While some of the ducks got sick and died, their owner never had any symptoms.

The CDC has been monitoring the health of more than 500 people in 25 states who were exposed to the infected birds, Davis said. Although a few dozen people did develop flu-like symptoms, all were tested but none were positive for the virus.

Supply disruptions

The virus also does not pose a special risk to the nation's food supply. The CDC states that for any poultry or eggs, proper handling and heating it to an internal temperature of 73 C kills any bacteria and viruses present, including any HPAI viruses.

The deaths of millions of egg-laying birds are driving the price of eggs up to historic levels for consumers and businesses alike, according to market research company Urner Barry.

"I am kind of holding my breath this month," Denise Heard, poultry veterinarian and vice-president of research for the US Poultry and Egg Association, told ABC News.

The bird flu outbreak that peaked in the late spring of 2015 was "the largest poultry health disaster in US history", the US Department of Agriculture said. It resulted in the deaths of more than 50 million birds and cost the poultry industry billions of dollars.

In January, government officials announced the arrival of bird flu in the US after a wigeon duck in South Carolina tested positive. It was then detected in Indiana in February. Scientists believe that wild migratory birds brought the virus to North America.