A recent bird flu outbreak at a mink farm has raised concerns about the virus spreading to humans more widely.
Scientists have been keeping tabs on this bird flu virus since the 1950s, although it was not considered a threat to humans until a 1997 outbreak in Hong Kong among visitors to live poultry markets.
As bird flu strikes more and more different animals, such as on the mink farm, the fear is that the virus could evolve to spread more easily between people, and could trigger a pandemic.
A different type of bird flu was likely behind the devastating flu pandemic of 1918-1919, and bird viruses played a role in other flu pandemics in 1957, 1968, and 2009, a scientist says.
Still, the risk to the general public is now low, says Dr. Tim Uyeki of the US Centers for Disease Control and Prevention.
A look at the bird flu virus and why it’s getting renewed attention:
WHAT IS BIRD FLU?
Some flu viruses primarily affect humans, while others occur primarily in animals. For example, there is influenza in dogs, as well as swine or swine flu viruses. And then there are avian viruses that spread naturally in wild waterfowl like ducks and geese, and then to chickens and other poultry.
The bird flu virus that draws attention today—Type A H5N1—was identified in 1959 by investigators looking at an outbreak of flu in chickens in Scotland. Like other viruses, it has evolved over time, spawning newer versions of itself.
By 2007, the virus was found in more than 60 countries. In the United States, it has recently been detected in wild birds in every state, as well as commercial poultry operations or backyard flocks in 47 states. Since the beginning of last year, thousands of chickens have died from the virus or been killed to stop outbreaks from spreading, one of the reasons cited for rising egg prices.
How often do people get bird flu?
The 1997 Hong Kong outbreak was the first time this bird flu was blamed for serious human illness. Of 18 people who were infected, six died. To contain the outbreak, the Hong Kong government closed live poultry markets, killed all the birds in the markets, and stopped importing chickens from southern China. It worked, for a while.
Symptoms are similar to other flus, including cough, body aches and fever. Some people don’t notice symptoms, but some develop badly. life-threatening pneumonia.
Worldwide, nearly 870 human infections and 457 deaths have been reported to the World Health Organization in 20 countries. But the pace is slow and there have been around 170 infections and 50 deaths in the last seven years. In the vast majority of cases, the infected people got it directly from infected birds.
The first and only US case happened just last April. It was picked up by a prison inmate in a program killing infected birds at a poultry farm in Montrose County, Colorado, in the west of the state. His only symptom was fatigue and he passed out.
CAN I SPREAD IT BETWEEN PEOPLE?
In some cases, the investigators concluded, the bird flu virus appears to have spread from person to person. That happened in Thailand, Vietnam, Indonesia, China and Pakistan, in 2007 recently.
In each cluster, it spreads within families from a sick person in the home. Scientists do not believe it can be easily spread through casual contact, as seasonal flu can. But viruses mutate and change. Scientists are concerned about the increasing number of opportunities for bird flu to mix with other flu viruses in infected humans or animals and mutate, making it easier to spread to humans.
It wouldn’t take much if that happened “and then we would be in a very tough situation,” said Dr. Luis Ostrosky, chief of infectious diseases and epidemiology at the University of Texas Health Science Center at Houston.
The CDC’s Uyeki said it was during the earliest clusters that he was most concerned about H5N1. That kind of person-to-person spread doesn’t seem to be happening right now, he said.
WHAT ABOUT THE SMALL FARM?
Concern among public health experts has recently been fueled, in part, by the detection of infections in various mammals. The growing list includes foxes, raccoons, skunks, bears and even marine mammals like seals and porpoises. Officials in Peru said three sea lions found dead in November had tested positive, and hundreds more may have died recently from bird flu.
Then last month, a European medical journal reported on an October bird flu outbreak at a mink farm in Spain with nearly 52,000 animals, where the illness spread like wildfire.
The mink was given poultry, and wild birds in the region were found to have bird flu. But researchers said however it started, they believe the virus then spreads from mink to mink – a worrying scenario. No workers were infected, although they wore masks as part of COVID-19 precautions.
Jennifer Nuzzo, director of the Pandemic Center at Brown University’s School of Public Health, said the virus outbreak is being watched for mutations that could make it easier to transmit to people, and possibly between people.
“That’s the real concern,” Nuzzo said.
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