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Bird flu is highly lethal to some animals, but not to others. Scientists want to know why

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Bird flu is highly lethal to some animals, but not to others. Scientists want to know why
News

News

Bird flu is highly lethal to some animals, but not to others. Scientists want to know why

2024-06-15 04:57 Last Updated At:05:00

NEW YORK (AP) — In the last two years, bird flu has been blamed for the deaths of millions of wild and domestic birds worldwide. It's killed legions of seals and sea lions, wiped out mink farms, and dispatched cats, dogs, skunks, foxes and even a polar bear.

But it seems to have hardly touched people.

That's "a little bit of a head scratcher,” although there are some likely explanations, said Richard Webby, a flu researcher at St. Jude Children’s Research Hospital in Memphis, Tennessee. It could have to do with how infection occurs or because species have differences in the microscopic docking points that flu viruses need to take root and multiply in cells, experts say.

But what keeps scientists awake at night is whether that situation will change.

“There's a lot we don't understand,” said Dr. Tom Frieden, a former CDC director who currently heads Resolve to Save Lives, a not-for-profit that works to prevent epidemics. “I think we have to get over the 'hope for the best and bury our head in the sand' approach. Because it could be really bad."

Some researchers theorize that flu viruses that originated in birds were the precursors to terrible scourges in humans, including pandemics in 1918 and 1957. Those viruses became deadly human contagions and spread in animals and people.

A number of experts think it’s unlikely this virus will become a deadly global contagion, based on current evidence. But that's not a sure bet.

Just in case, U.S. health officials are readying vaccines and making other preparations. But they are holding off on bolder steps because the virus isn't causing severe disease in people and they have no strong evidence it’s spreading from person to person.

The flu that's currently spreading — known as H5N1 — was first identified in birds in 1959. It didn’t really begin to worry health officials until a Hong Kong outbreak in 1997 that involved severe human illnesses and deaths.

It has caused hundreds of deaths around the world, the vast majority of them involving direct contact between people and infected birds. When there was apparent spread between people, it involved very close and extended contact within households.

Like other viruses, however, the H5N1 virus has mutated over time. In the last few years, one particular strain has spread alarmingly quickly and widely.

In the United States, animal outbreaks have been reported at dozens of dairy cow farms and more than 1,000 poultry flocks, according to the U.S. Department of Agriculture. Four human infections have been reported among the hundreds of thousands of people who work at U.S. poultry and dairy farms, though that may be an undercount.

Worldwide, doctors have detected 15 human infections caused by the widely circulating bird flu strain. The count includes one death — a 38-year-old woman in southern China in 2022 — but most people had either no symptoms or only mild ones, according to the U.S. Centers for Disease Control and Prevention.

There's no way to know how many animals have been infected, but certain creatures seem to be getting more severe illnesses.

Take cats, for example. Flu is commonly thought of as a disease of the lungs, but the virus can attack and multiply in other parts of the body too. In cats, scientists have found the virus attacking the brain, damaging and clotting blood vessels and causing seizures and death.

Similarly gruesome deaths have been reported in other animals, including foxes that ate dead, infected birds.

The flu strain's ability to lodge in the brain and nervous system is one possible reason for "higher mortality rate in some species,” said Amy Baker, an Iowa-based U.S. Department of Agriculture scientist who studies bird flu in animals. But scientists "just don’t know what the properties of the virus or the properties of the host are that are leading to these differences,” Baker said.

Unlike cats, cows have been largely spared. Illnesses have been reported in less than 10% of the cows in affected dairy herds, according to the USDA. Those that did develop symptoms experienced fever, lethargy, decreased appetite and increased respiratory secretions.

Cow infections largely have been concentrated in the udders of lactating animals. Researchers investigating cat deaths at dairy farms with infected cows concluded the felines caught the virus from drinking raw milk.

Researchers are still sorting out how the virus has been spreading from cow to cow, but studies suggest the main route of exposure is not the kind of airborne droplets associated with coughing and sneezing. Instead it's thought to be direct contact, perhaps through shared milking equipment or spread by the workers who milk them.

Then there's the issue of susceptibility. Flu virus need to be able to latch onto cells before they can invade them.

“If it doesn't get into a cell, nothing happens. ... The virus just swims around,” explained Juergen Richt, a researcher at Kansas State University.

But those docking spots — sialic acid receptors — aren't found uniformly throughout the body, and differ among species. One recent study documented the presence of bird flu-friendly receptors in dairy cattle mammary glands.

Eye redness has been a common symptom among people infected by the current bird flu strain. People who milk cows are eye level with the udders, and splashes are common. Some scientists also note that the human eye has receptors that the virus can bind to.

A study published this month found ferrets infected in the eyes ended up dying, as the researchers demonstrated that the virus could be as deadly entering through the eyes as through the respiratory tract.

Why didn't the same happen in the U.S. farmworkers?

Some experts wonder whether people have some level of immunity, due to past exposure to other forms of flu or to vaccinations. However, a study in which human blood samples were exposed to the virus indicated there's little to no existing immunity to this version of the virus, including among people who'd had seasonal flu shots.

A more menacing question: What happens if the virus mutates in a way that makes it more lethal to people or allows it to spread more easily?

Pigs are a concern because they are considered ideal mixing vessels for bird flu to potentially combine with other flu viruses to create something more dangerous. Baker has been studying the current strain in pigs and found it can replicate in the lungs, but the disease is very mild.

But that could all change, which is why there's a push in the scientific community to ramp up animal testing.

Frieden, of Resolve to Save Lives, noted public health experts have been worried about a deadly new flu pandemic for a long time.

“The only thing predictable about influenza is it's unpredictable,” he said.

The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Science and Educational Media Group. The AP is solely responsible for all content.

FILE - A dead sea bird lays beside a dead sea lion on the beach at Punta Bermeja, on the Atlantic coast of the Patagonian province of Río Negro, near Viedma, Argentina, Monday, Aug. 28, 2023. Government experts suspect that bird flu is killing sea lions along Argentina's entire Atlantic coastline, causing authorities to close many beaches in order to prevent the virus from spreading further. (AP Photo/Juan Macri, File)

FILE - A dead sea bird lays beside a dead sea lion on the beach at Punta Bermeja, on the Atlantic coast of the Patagonian province of Río Negro, near Viedma, Argentina, Monday, Aug. 28, 2023. Government experts suspect that bird flu is killing sea lions along Argentina's entire Atlantic coastline, causing authorities to close many beaches in order to prevent the virus from spreading further. (AP Photo/Juan Macri, File)

Next Article

What to know about the attempt on Trump's life and its aftermath

2024-07-16 00:25 Last Updated At:00:31

The FBI is still trying to determine a motive behind Saturday's attempt to assassinate former President Donald Trump, while the tone of this week's Republican convention in Milwaukee likely will be dominated by the violence.

A former fire chief who was killed at Trump's Pennsylvania rally is being remembered as a “man of conviction."

The shooting wounded two other men and pierced the upper part of Trumps’ ear with a bullet. The 20-year-old who authorities say carried out the attack is believed to have acted alone with his father's gun.

Here’s a look at what we know so far about the attempt on Trump's life and its aftermath:

Officials say Thomas Matthew Crooks, 20, of Bethel Park, Pennsylvania — about 50 miles (80 kilometers) from the shooting — first came to law enforcement’s attention when spectators at the Trump rally noticed him acting strangely outside the event. Specifically, he was pacing near the magnetometers, according to a law enforcement official who spoke on the condition of anonymity because they were not authorized to discuss the investigation.

The gunman made it to a nearby roof with an AR-style rifle and a local law enforcement officer climbed to the roof and found Crooks, who pointed the rifle at the officer, Butler County Sheriff Michael Slupe told The Associated Press. The officer retreated down the ladder, and the gunman quickly fired toward Trump.

Trump was showing off a chart of border crossing numbers when the gunfire began.

As the first pop went off Trump said, “Oh," then raised his hand to his right ear and looked at it before quickly crouching to the ground behind his lectern.

Someone could be heard near the microphone saying, “Get down, get down, get down, get down!” as agents rushed to the stage. They piled atop the former president to shield him with their bodies as other agents took up positions on stage to search for the threat.

U.S. Secret Service gunmen shot the gunman, officials said.

Trump later said the upper part of his right ear was pierced by a bullet. His aides said he was in “great spirits” and doing well. He arrived in Milwaukee on Sunday evening for the convention, which begins Monday.

Investigators are hunting for clues and the absence of any clear ideological motive so far has led conspiracy theories to flourish.

The FBI said it believes Crooks acted alone. Investigators have found no threatening comments on social media accounts or ideological positions that could help explain what led him to target Trump.

Crooks graduated from Bethel Park High School in 2022. An FBI official told reporters that Crooks’ family is cooperating with investigators.

Crooks’ political leanings were not immediately clear. Records show Crooks was registered as a Republican voter in Pennsylvania, but federal campaign finance reports also show he gave $15 to a progressive political action committee on Jan. 20, 2021, the day Biden was sworn into office.

Jason Kohler, who said he attended the same high school but did not share any classes with Crooks, said Crooks was bullied at school and sat alone at lunchtime. Other students mocked him for the clothes he wore, which included hunting outfits, Kohler said.

“He was just a outcast, and you know how kids are nowadays,” Kohler told reporters.

Crooks worked at a nursing home as a dietary aide, a job that generally involves food preparation. Marcie Grimm, the administrator of Bethel Park Skilled Nursing and Rehabilitation, said in a statement she was “shocked and saddened to learn of his involvement.” Grimm added that Crooks had a clean background check when he was hired.

The FBI is investigating the shooting as a potential act of domestic terrorism and questions abounded about how the gunman got so close in the first place.

Kevin Rojek, the agent in charge of the FBI’s Pittsburgh field office, said “it is surprising” the gunman was able to open fire on the stage before the Secret Service killed him.

Bomb-making materials were found inside both Crooks’ vehicle and at his home, officials said. The FBI described the devices as “rudimentary.”

Gov. Josh Shapiro on Sunday said the man killed at the Trump rally, Corey Comperatore, “dove on his family to protect them.”

“Corey died a hero,” the governor said. Comperatore, 50, was a former fire chief.

Pennsylvania State Police identified two other men who were shot as David Dutch, 57, of New Kensington, and James Copenhaver, 74, of Moon Township. Both men remained hospitalized and were listed in stable condition, state police said.

Comperatore’s quick decision to use his body as a shield against the bullets flying toward his wife and daughter rang true to the close friends and neighbors who loved and respected the proud 50-year-old Trump supporter, noting that the Butler County resident was a “man of conviction.”

“He’s a literal hero. He shoved his family out of the way, and he got killed for them,” said Mike Morehouse, who lived next to Comperatore for the last eight years. “He’s a hero that I was happy to have as a neighbor.”

Randy Reamer, president of the Buffalo Township volunteer fire company, called Comperatore “a stand-up guy” and “a true brother of the fire service.” He said Comperatore served as chief of the company for about three years but was also a life member, meaning he had served for more than 20 years.

“Just a great all-around guy, always willing to help someone out,” Reamer said of Comperatore. “He definitely stood up for what he believed in, never backed down to anyone. … He was a really good guy.”

The Republican National Convention starts Monday, with Trump and his advisers pledging resilience in the face of the attack. The four-day event will showcase the former president and his platform as his party formally chooses him to be its nominee.

It was not immediately clear if and how Saturday’s attack would alter the convention, which normally has a celebratory atmosphere. Republican officials have said they want to defy the threat Trump has faced and stick to their plans and their schedule. But at the very least, the event is expected to include a heightened focus on security and a grim recognition of how stunningly close Trump came to losing his life.

The presumptive Republican nominee and his allies will face the nation unquestionably united and ready to “fight,” as the bloodied Trump cried out Saturday while Secret Service agents at his Pennsylvania rally rushed him to safety.

Anger and anxiety are coursing through the party, even as many top Republicans call for calm and a lowering of tensions. As elected officials, politicians and a few regular Americans address the conference, the question is which tone will prevail in the aftermath of the attack: Will it make speeches even more fiery or will calls for calm prevail?

People rally in support of Republican presidential candidate former President Donald Trump in Huntington Beach, Calif., Sunday, July 14, 2024. (AP Photo/Eric Thayer)

People rally in support of Republican presidential candidate former President Donald Trump in Huntington Beach, Calif., Sunday, July 14, 2024. (AP Photo/Eric Thayer)

Members of an honor guard are reflected in a mylar wall, left, during a rehearsal for the 2024 Republican National Convention on Sunday, July 14, 2024, in Milwaukee. (AP Photo/Charles Rex Arbogast)

Members of an honor guard are reflected in a mylar wall, left, during a rehearsal for the 2024 Republican National Convention on Sunday, July 14, 2024, in Milwaukee. (AP Photo/Charles Rex Arbogast)

Former President Trump waves to supporters after arriving to the Milwaukee Mitchell International Airport ahead of the 2024 Republican National Convention, Sunday, July 14, 2024, in Milwaukee. (AP Photo/Alex Brandon)

Former President Trump waves to supporters after arriving to the Milwaukee Mitchell International Airport ahead of the 2024 Republican National Convention, Sunday, July 14, 2024, in Milwaukee. (AP Photo/Alex Brandon)

This undated photo provided by the Buffalo Township, Pa., Volunteer Fire Company shows former Buffalo Township Fire Chief Corey Comperatore. Comperatore was killed during a shooting at a campaign rally for Republican presidential candidate former President Donald Trump in Butler, Pa., on Saturday. (Buffalo Township Volunteer Fire Company via AP)

This undated photo provided by the Buffalo Township, Pa., Volunteer Fire Company shows former Buffalo Township Fire Chief Corey Comperatore. Comperatore was killed during a shooting at a campaign rally for Republican presidential candidate former President Donald Trump in Butler, Pa., on Saturday. (Buffalo Township Volunteer Fire Company via AP)

An automobile license plate at the Buffalo Township Fire Company 27 is wrapped in black bunting in Buffalo Township, Pa., Sunday, July 14, 2024. Firefighter Corey Comperatore was killed during a shooting at a campaign rally for Republican presidential candidate former President Donald Trump in Butler, Pa., on Saturday. (AP Photo/Sue Ogrocki)

An automobile license plate at the Buffalo Township Fire Company 27 is wrapped in black bunting in Buffalo Township, Pa., Sunday, July 14, 2024. Firefighter Corey Comperatore was killed during a shooting at a campaign rally for Republican presidential candidate former President Donald Trump in Butler, Pa., on Saturday. (AP Photo/Sue Ogrocki)

A person watches news in a local bar near the Fiserv Forum watching news ahead of the 2024 Republican National Convention, Saturday, July 13, 2024, in Milwaukee. Former president Donald Trump was whisked off the stage at a rally in Butler, Pennsylvania after apparent gunshots rang through the crowd.(AP Photo/Matt Rourke)

A person watches news in a local bar near the Fiserv Forum watching news ahead of the 2024 Republican National Convention, Saturday, July 13, 2024, in Milwaukee. Former president Donald Trump was whisked off the stage at a rally in Butler, Pennsylvania after apparent gunshots rang through the crowd.(AP Photo/Matt Rourke)

President Joe Biden addresses the nation from the Oval Office of the White House in Washington, Sunday, July 14, 2024, about the assassination attempt of Republican presidential candidate former President Donald Trump at a campaign rally in Pennsylvania. (Erin Schaff/The New York Times via AP, Pool)

President Joe Biden addresses the nation from the Oval Office of the White House in Washington, Sunday, July 14, 2024, about the assassination attempt of Republican presidential candidate former President Donald Trump at a campaign rally in Pennsylvania. (Erin Schaff/The New York Times via AP, Pool)

Law enforcement block a street in Bethel Park, Pa., that they say is near a residence of Thomas Matthew Crooks, the suspected shooter of former President Donald Trump, Sunday, July 14, 2024. (AP Photo/Joshua A. Bickel)

Law enforcement block a street in Bethel Park, Pa., that they say is near a residence of Thomas Matthew Crooks, the suspected shooter of former President Donald Trump, Sunday, July 14, 2024. (AP Photo/Joshua A. Bickel)

This 2021 photo provided by Bethel Park School District shows student Thomas Matthew Crooks who graduated from Bethel Park High School with the Class of 2022, in Bethel Park, Pa. Crooks was identified by the FBI as the shooter involved in an assassination attempt of former President Donald Trump at a campaign rally on Saturday, July 13, 2024, in Butler, Pa. (Bethel Park School District via AP)

This 2021 photo provided by Bethel Park School District shows student Thomas Matthew Crooks who graduated from Bethel Park High School with the Class of 2022, in Bethel Park, Pa. Crooks was identified by the FBI as the shooter involved in an assassination attempt of former President Donald Trump at a campaign rally on Saturday, July 13, 2024, in Butler, Pa. (Bethel Park School District via AP)

Police snipers return fire after shots were fired while Republican presidential candidate former President Donald Trump was speaking at a campaign event in Butler, Pa., on Saturday, July 13, 2024. (AP Photo/Gene J. Puskar)

Police snipers return fire after shots were fired while Republican presidential candidate former President Donald Trump was speaking at a campaign event in Butler, Pa., on Saturday, July 13, 2024. (AP Photo/Gene J. Puskar)

Republican presidential candidate former President Donald Trump is moved from the stage at a campaign rally, Saturday, July 13, 2024, in Butler, Pa. (AP Photo/Evan Vucci)

Republican presidential candidate former President Donald Trump is moved from the stage at a campaign rally, Saturday, July 13, 2024, in Butler, Pa. (AP Photo/Evan Vucci)

A campaign rally site for Republican presidential candidate former President Donald Trump is empty and littered with debris Saturday, July 13, 2024, in Butler, Pa. (AP Photo/Evan Vucci)

A campaign rally site for Republican presidential candidate former President Donald Trump is empty and littered with debris Saturday, July 13, 2024, in Butler, Pa. (AP Photo/Evan Vucci)

Kevin Rojek, left, FBI special agent in charge, Lt. Col. George Givens, center, Pennsylvania State Police, and Col. Christopher Paris, right, Pennsylvania State Police, answer questions at a news conference concerning the assassination attempt on former President Donald Trump, Saturday, July 13, 2024, in Butler, Pa. (AP Photo/Sue Ogrocki

Kevin Rojek, left, FBI special agent in charge, Lt. Col. George Givens, center, Pennsylvania State Police, and Col. Christopher Paris, right, Pennsylvania State Police, answer questions at a news conference concerning the assassination attempt on former President Donald Trump, Saturday, July 13, 2024, in Butler, Pa. (AP Photo/Sue Ogrocki

Republican presidential candidate former President Donald Trump addresses the crowd at a campaign event in Butler, Pa., on Saturday, July 13, 2024. (AP Photo/Gene J. Puskar)

Republican presidential candidate former President Donald Trump addresses the crowd at a campaign event in Butler, Pa., on Saturday, July 13, 2024. (AP Photo/Gene J. Puskar)

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