Workers prepare ducks at a market in Phnom Penh, Cambodia February 24, 2023. Two people in Cambodia have been confirmed to have been infected with the H5N1 bird flu, but it appears to have been the result of exposure to infected birds or poultry.
(Photo by TANG CHHIN SOTHY/AFP via Getty Images)
- An overflow probably happens every day somewhere in the world, according to an expert.
- The European Center for Disease Control warns that mutations found in the H5N1 bird flu virus are “worrying”.
- The United States is experiencing a massive outbreak of bird flu that has spread to mammals.
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In the wake of the COVID-19 pandemic, outbreaks of viruses such as avian flu that we keep hearing about could lead us to fear that another disease may jump or spread from animals to humans.
Just this week, the European Center for Disease Control warned that mutations found in the H5N1 bird flu virus are “worrying”. This could suggest the potential for bird flu to spread to humans is increasing, the center said.
“The expansion of mammalian species identified as infected with A(H5N1) viruses as well as the detection of viruses carrying mammalian adaptation markers in other genes such as PB2 that correlate with replication and increased virulence in mammals, is of concern,” the center said. said in a report.
“With the wide geographical distribution of avian influenza viruses and the high number of detections also in wild birds and mammals, sporadic human cases infected with HPAI (highly pathogenic avian influenza) viruses cannot be excluded whenever people are exposed to sick or dead infected birds,” the report said.
The center said the threat in Europe remained low for the general public and low to moderate for people in frequent contact with birds, however, the risk assessments contain “high uncertainty”.
In the United States, which is experiencing an outbreak of bird flu in at least 47 states, the virus has spread to mink, foxes, raccoons and bears. And this week, scientists confirmed that the virus had infected some of the 150 New England harbor and gray seals found dead or sick along the Maine coast last summer. In some of the seals, the virus had mutations associated with adaptation to mammals.
(SEAL DEATHS: Maine seals are dying in unusually high numbers)
Last month, two people in Cambodia were confirmed to have been infected with the H5N1 avian flu, but this appears to have been the result of exposure to infected birds or poultry and not human-to-human transmission, according to officials. United States Centers for Disease Control and Prevention. . This strain of the virus is different from the H5N1 viruses currently spreading among wild birds and poultry in the United States, the CDC said.
To learn more about how this “spillover” happens (and how to prevent it), we spoke with Dr. Treana Mayer, veterinarian and post-doctoral fellow in microbiology at Colorado State University. Here’s our conversation, edited for clarity.
Can you give us a brief definition of overflow?
Spillover is an event when a contagious disease passes from animals to humans. Usually people are not a typical host for the disease. It could be a totally new disease, like when COVID-19 first spread to humans, or it could be a well-known disease in animals that is unusual to see. find in humans.
What is the frequency of overflows with viruses?
It is much more common than scientists previously thought. Fallout is likely happening every day somewhere in the world, given how close we live and work with animals and how diverse viruses are. However, many of these spillover events do not lead to larger outbreaks, but die out on their own.
Are all viruses capable of overflowing? What makes a virus conducive to spreading?
No, fortunately not all viruses in animals are able to spread to humans. There are many obstacles for a virus to enter and cause illness in people. Some viruses are naturally more flexible and can move between species more easily. Some viruses can mutate very quickly, including coronaviruses like the one responsible for COVID-19, and influenza viruses. This means that they could eventually acquire the ability to infect humans through random changes to their genetic code. Finally, if the virus is normally found in animals closer to humans, such as primates, the leap to humans is easier for the virus, with less biological distance to cross.
Overflow is a metaphor. How does this metaphor help us understand what can happen?
The dictionary definition of overflow is usually an unintended consequence of something in excess. If we think of the simplest example of a cup that is overfilled with water, the water will spill over the rim and splash everything nearby. We can think of this cup as a population of animals, water being a disease capable of infecting people, and us humans in the splash zone. This is a useful metaphor because the rate and severity of animal infections and the closeness of our interactions with these diseased animals are all important to the likelihood of a spillover occurring.
What can humans do to reduce the risk of future viral spread?
There are two main areas we can focus on: first, preventing spills at source, which often come from wildlife. With climate change, habitat loss and land use changes, wildlife diseases are more likely to mutate and spread as animals are stressed, crowded and on the move. We need to protect natural areas and keep wildlife separate from us and our farm animals. And second, to improve our ability to detect new overflow events early, before they spiral out of control. This includes detecting new diseases in animals and humans.
Who should be worried about fallout happening to them?
Those most at risk of spread are those who are most likely to contact large numbers of sick animals without taking protective measures such as good hygiene or wearing gloves and masks. These may be people working with farm animals, in the wildlife trade, or communities encroaching on previously wild land during animal disease outbreaks. Spillover only becomes a threat to the general public if the disease adapts to our human biology. This usually happens after repeated overflows, so early detection and prevention of future overflows is vitally important.
LEARN MORE ABOUT BIRD INFLUENZA
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