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NEW YORK – A recent outbreak of bird flu at a mink farm has reignited concerns about the virus spreading more widely to humans.
Scientists have been monitoring this bird flu virus since the 1950s, although it was not considered a threat to people until a 1997 outbreak in Hong Kong among visitors to live poultry markets.
As bird flu strikes more and more animals, such as mink, the fear is that the virus could evolve to spread more easily between people, potentially triggering a pandemic.
Scientists say another 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.
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 garnering renewed attention:
What is bird flu?
Some influenza viruses primarily affect humans, but others occur primarily in animals. For example, there are cases of flu that occur 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 in chickens and other domestic poultry.
The bird flu virus that is now attracting attention – Type A H5N1 – was first identified in 1959, by investigators investigating an outbreak of influenza in chickens in Scotland. Like other viruses, it has evolved over time, spawning new versions of itself.
In 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 in commercial poultry farms or backyard flocks in 47 states. Since the start of last year, tens of millions of chickens have died from the virus or been killed to prevent the spread of outbreaks, one of the reasons given for the spike in egg prices.
How often do you catch bird flu?
The Hong Kong outbreak in 1997 was the first time this bird flu was blamed for serious human illness. Of 18 people infected, six died. To contain the outbreak, the Hong Kong government shut down live poultry markets, killed all birds in the markets and stopped importing chickens from southern China. It worked, for a while.
Symptoms are similar to other cases of the flu, including cough, body aches and fever. Some people have no noticeable symptoms, but some develop a severe form. life-threatening pneumonia.
Globally, nearly 870 human infections and 457 deaths have been reported to the World Health Organization in 20 countries. But the pace has slowed and there have been around 170 infections and 50 deaths over the past seven years. In the vast majority of cases, infected people got it directly from infected birds.
The first and only US case occurred last April. An inmate in a work program caught it by killing infected birds at a poultry farm in Montrose County, Colorado, in the western part of the state. His only symptom was fatigue and he recovered.
Can it spread between people?
In some cases, investigators concluded that the bird flu virus had apparently spread from person to person. This has happened in Thailand, Vietnam, Indonesia, China and Pakistan, most recently in 2007.
In each cluster, it spread within families from a sick person at home. Scientists don’t believe it can spread easily through casual contact, as seasonal flu can. But viruses mutate and change. Scientists are concerned about the ever-increasing number of opportunities for bird flu to mix with other flu viruses in infected people or animals and mutate, making it easier to spread to humans.
It wouldn’t take much for that to happen “and then we’d be in a really tough spot,” said Dr. Luis Ostrosky, chief of infectious diseases and epidemiology at the Center for Health Sciences. University of Texas at Houston.
CDC’s Uyeki said the most worried about H5N1 he has been in previous clusters. That kind of human-to-human spread doesn’t seem to be happening right now, he said.
What happened at the mink farm?
Recent concern among public health experts has 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. Peruvian officials said three sea lions found dead in November had tested positive and the recent deaths of hundreds more could be due to bird flu.
Then last month, a European medical journal reported an outbreak of bird flu in October at a mink farm in Spain with nearly 52,000 animals, where the disease spread like wildfire.
The mink were fed poultry and the wild birds in the area had bird flu. But the researchers said that regardless of how it started, they believe the virus then spread 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 School of Public Health, said the outbreak virus is being monitored for mutations that could make it more easily transmissible to people, and potentially between people.
“That’s the real worry,” Nuzzo said.