In February, an 11-year-old girl in Cambodia died after contracting bird flu.
Avian influenza is now raging in Japan, and the number of poultry farms where outbreaks have been confirmed and the number of chickens being disposed of has reached a record high.
The type of virus detected is highly pathogenic "H5N1".
Furthermore, there has been disturbing information that the virus has been detected in mammals that are closely related to humans.
How likely is it that this virus will spread among humans?
How vigilant should we be?
I will tell you in detail.
Cambodian girl dies after being infected by bird
On February 24, WHO = World Health Organization announced that an 11-year-old girl in Cambodia died after being infected with the bird flu virus.
The WHO reported that the girl began showing symptoms on February 16.
She then developed severe pneumonia and was treated at a national children's hospital, where she died on the 22nd.
What was detected was a highly pathogenic "H5N1" type avian influenza virus, the same type as the virus spreading to chickens and other animals around the world.
The infection was confirmed in her deceased girl and her father, but her father did not develop symptoms.
The two infected people had the opportunity to come into contact with infected birds in an environment where birds were kept.
Upon further examination of the detected virus, it is believed to be a case of infection from birds to humans, as it was the same strain as the one that has been spreading in chickens in Southeast Asia since 2014.
Avian flu raging around the world
Avian influenza is a virus originally found in waterfowl such as ducks, and it infects chickens and other birds through feces, causing respiratory symptoms such as coughing.
A virus with a high lethality that kills more than 75% of infected chickens within 10 days is treated as 'highly pathogenic'.
Influenza viruses are classified by two types of proteins on the surface of the virus, indicated by the letters "H" and "N", and the currently spreading "H5N1" type is a typical highly pathogenic avian influenza virus. is.
In Japan, avian influenza is thought to be brought in by migratory birds over the winter, and outbreaks occur from autumn to spring every year.
Even in Japan, this season has spread at an unprecedented pace, with wild birds starting in September 2022, the earliest season so far, and chickens from poultry farms starting in October.
The number of poultry farms where outbreaks have been confirmed is 78 in 25 prefectures, and the number of chickens to be disposed of exceeds 15 million, both of which are new records (March 6, 2023). the current).
The "H5N1" virus continues to spread around the world.
Since July 2022 alone, it has been confirmed one after another in Asia, Europe, Africa, North America and South America, and the poultry farming industry has been severely damaged in various places.
"H5N1" type There are cases of human infection and death overseas
Bird flu has occasionally infected humans.
Cases of death due to infection with the "H5N1" avian influenza virus, which has been regarded as highly pathogenic, have been reported for some time.
In 1997, the first human infection was confirmed during a large outbreak at a poultry farm in Hong Kong, and 6 of the 18 people who complained of symptoms died.
According to WHO, from 2003 to 25 February 2023, 873 people were infected and 458 died in 21 countries.
The fatality rate is 52%, and more than half of confirmed infections have died.
What are the symptoms of human-to-human transmission?
No cases of the disease have been confirmed in Japan so far.
Human infection is rare, and it is said that people who come into direct contact with infected birds, droppings, or carcasses are infected.
Human-to-human transmission is not as easy as the new corona, and cases of human-to-human transmission are limited to family members who have been in close contact for a long time.
However, global vigilance remains as more outbreaks in birds increase the likelihood of infecting humans.
According to the website of the prime minister's official residence, infection causes high fever, cough, difficulty breathing, and pneumonia in many cases.
It is necessary to receive treatment such as anti-influenza drugs as soon as possible because abnormalities may appear in the organs of the whole body and cause death.
The risk of human infection is low, but...
According to WHO, ``The H5 virus has not acquired the ability to continue to infect humans, and the risk to the general public is low.''
However, because vaccines for H5N1 bird flu are not widely available, people who work with birds, such as poultry farmers, should be vaccinated against seasonal flu.
By doing so, we should prevent multiple viruses from combining in humans to create new types of viruses that are easy to spread among humans.
In addition, the "H5N1" type avian influenza virus, which was also detected in Cambodia by the CDC = Center for Disease Control in the United States, has a gene mutation that makes it easier to spread infection among humans and weakens the effect of anti-influenza drugs. was not confirmed.
Yoshihiro Sakoda, a professor at Hokkaido University who is familiar with infectious diseases between humans and animals, says that in Japan, where people rarely come into contact with birds, they do not get infected if they are careful. Because there is, I think that attention is necessary.
“It is known that there is a bird-shaped virus receptor (the part where the virus binds) in the back of the human lung. There is a risk of bird-to-human transmission, so if poultry farm workers and zookeepers are warned enough, bird-to-human transmission will not occur in Japan. do not have"
A series of reports of infection in mammals
But the story doesn't end there.
Around the world, mammals, which are closely related to humans, are being infected with avian influenza one after another.
The H5N1 virus has been detected in some of the hundreds of sea lions that have died off the coast of Peru in recent months.
In addition, the "H5N1" type virus was confirmed to be infected with wild bears and foxes in the United States in 2022.
In Spain, there have been reports of suspected cases of infection between minks at mink breeding farms.
In Japan, the "H5N1" type virus was also detected in the carcasses of Ezo red foxes and debilitated raccoon dogs collected in Sapporo in March and April 2022.
According to the Hokkaido University group that conducted the research, this is the first confirmed case of mammalian infection in Japan.
The same virus was also detected in the carcasses of crows that were eaten by the red fox and raccoon dog, and it is believed that the virus was transmitted from migratory birds to mammals via crows.
Mammal monitoring Take measures against birds
The virus that spread in 2009 at the time of the "swine flu" was a combination of swine virus, bird virus, and human virus.
A new influenza virus emerged in mammalian pigs and spread to humans.
Professor Sakoda of Hokkaido University emphasizes the need to monitor whether avian influenza viruses, which are likely to spread in mammals, mutate and infect humans as infection with avian influenza viruses becomes established among wild mammals. increase.
“The virus spreads to wild birds at an uncontrollable speed, and infections are spreading across species to wild mammals that feed on them. has been isolated, and cross-species viral transmission in wild mammals has entered a new stage.Mammals and humans sometimes come into contact.The virus originally came from birds, but from wild mammals to humans. We researchers are concerned about this scenario: Will it lead to the transmission of a highly pathogenic avian influenza virus among wild mammals, or will it be a transient infection? I think that it will end with this, and I think that we need to conduct thorough monitoring and information sharing."
Professor Sakoda also emphasizes that it is necessary to continue to take measures against birds on a global level and reduce the risk of spreading among humans in the future. .
“The number one point that requires attention is measures against wild birds to prevent sparks (viruses) from coming, and measures at poultry farms. It is necessary to take proper measures against birds."
"If outbreaks at poultry farms and cases of infection among wild birds are reduced, the risk of infection to mammals will be reduced, so the risk of becoming a pandemic in the future will also be reduced."