"Wake-up call": what could threaten the first case of human transmission of the H3N8 avian influenza virus

For the first time in history, scientists have recorded a case of human infection with the H3N8 avian influenza virus.

This happened in the Chinese province of Henan - the virus was detected in a four-year-old boy whose family lives in the city of Zhumadian.

The first symptoms of the disease (fever) appeared in the child on April 5, and a few days later he was hospitalized due to a deterioration in his health.

This was announced on April 26 by the State Committee of the People's Republic of China for Health.

In Henan province, preventive work was launched, and experts were mobilized to assess the risks.

The H3N8 virus "is of avian origin and has not previously been able to effectively infect humans," the agency said.

It is known that the family of the sick child raised chickens, and wild ducks were found near the house.

"This case represents an accidental cross-species transmission of the virus from a bird to a person, and the risk of large-scale spread of the virus is low," the National Health Commission of the People's Republic of China said.

The agency advised the public to avoid contact with dead poultry in their daily lives, to prevent direct contact with live birds as much as possible, and to monitor food hygiene.

“In case of a rise in temperature and detection of respiratory symptoms, it is necessary to wear a mask and immediately consult a doctor,” the State Committee website says.

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Rospotrebnadzor drew attention to the message of the Chinese authorities.

“The case of a four-year-old boy living in Henan province is currently considered to be isolated.

H3N8 has been knocking on the door for decades.

Rospotrebnadzor continues to monitor the development of the situation around the spread of this strain," the department told TASS.

unstable virus

Modern science distinguishes four types of influenza viruses: A, B, C and D. Groups A and B viruses circulate in the human population as seasonal diseases.

However, only type A viruses have caused pandemics in the entire history of observations. For example, the so-called Spanish flu pandemic, which claimed about 50 million human lives at the beginning of the 20th century, was caused by the H1N1 subtype virus.

As explained in an interview with RT by the head of the laboratory of bionanotechnology, microbiology and virology of the Faculty of Natural Sciences of Novosibirsk State University, Doctor of Biological Sciences, Corresponding Member of the Russian Academy of Sciences Professor Sergey Netesov, in fact, all influenza viruses are bird viruses, and only sometimes they “jump over” on people, adapt and become pathogenic for them.

“To date, strains and sub-variants of two influenza virus subtypes, H1N1 and H3N2, have established themselves in the human population and are already circulating independently of birds.

It happens that sometimes other subtypes / subtypes of the influenza virus also “jump” to people.

But this does not mean that an epidemic will certainly arise among people, each case must be considered separately, ”the scientist explained.

As for the virus subtype H3N8, it was discovered several decades ago in migratory waterfowl, which are the natural reservoir for all influenza viruses.

The virus also infects domestic animals such as horses and dogs.

In 2004, the attention of scientists was attracted by an outbreak of a then unknown respiratory disease in dogs in the United States - the disease initially spread among greyhounds.

As it was possible to establish, its causative agent was the influenza A (H3N8) virus, it was transmitted to dogs from horses.

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Most affected dogs had mild symptoms, such as cough and mild fever.

The animals later recovered.

But some of the dogs died: death occurred instantly, accompanied by severe bleeding in the lungs and pleural cavity.

“A histological study showed the presence (in dead dogs. -

) of tracheitis, bronchitis, bronchiolitis and purulent bronchopneumonia caused by significant erosion of epithelial cells and penetration of neutrophils,” says a scientific article published in 2008 by a group of American scientists in the journal Emerging Infectious Diseases

According to experts, the mortality rate among dogs as a result of infection with H3N8 ranged from 5% to 8%.

The outbreak of H3N8 in dogs caused such an outcry that representatives of the US Centers for Disease Control and Prevention (CDC) held a special press conference in September 2005, during which they tried to clarify the situation.

The researchers said at the time that there was no reason to panic, since in decades of observing H3N8, the virus had never been transmitted to humans.

“I also wanted to point out the fact that the virus ... is unstable in the laboratory and potentially resistant in humans to antiviral drugs,” said then Dr. Ruben Donis, who represented the CDC.

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In 2009, the USDA announced that it had approved the first H3N8 vaccine for animals.

However, a specific vaccine against H3N8 has not yet been developed for humans.

"Recombination of parts of the virus"

The H3N8 flu was brought up again in 2011 when scientists discovered that the virus was killing seals.

More than 160 animals have been found dead or dying on the northeast coast of the United States.

The researchers determined that the cause of their death was the H3N8 virus.

A group of American scientists studied the pathogen isolated from seals.

In particular, it was decided to test whether seasonal influenza vaccination could somehow help in the case of H3N8.

As a result of the study, it became clear that there is no herd immunity to H3N8 avian influenza even among people vaccinated against the seasonal H3 virus.

“The transmissibility (transmissible diseases - human diseases caused by parasites, viruses and bacteria, and diseases transmitted by vectors. -

) of the H3N8 influenza carried by the seal, combined with the apparent lack of immunity, raise concerns regarding these strains,” the article says, published as a result of a study in the journal Nature Communications in 2014.

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Another cause for concern was the fact that the virus has long gone beyond the bird population and is spreading among mammals.

According to Professor Ian Lipkin of Columbia University, seals acted as intermediaries: their cells have receptors for both avian flu and mammalian flu.

“That is, it turns out that this is a carrier in which such a virus can adapt, evolve and become more “mammalian” in its phenotype and more capable of causing disease in mammals ... That's when you need to seriously worry that it can be transmitted to humans, ” — said the scientist in 2012 in the comments of the BBC.

Today, experts urge not to panic over the news of the first case of human transmission of the virus, but remind that the potential threat to humans remains.

As Sergei Netesov noted, the case of human infection with H3N8 is still unique and is being carefully studied in China.

“The chance of it becoming a new human pathogen is low.

If only because it has been found among birds for a long time, and this case in humans is the first, ”said the professor.

In turn, Corresponding Member of the Russian Academy of Sciences, Professor and Chief Researcher of the Institute of Molecular Biology of the Russian Academy of Sciences Pyotr Chumakov holds a slightly different point of view.

According to him, the key question that Chinese experts should find an answer to in the near future is whether the virus has begun to be transmitted from person to person.

“If in this case it was possible to localize the disease, then this could be an alarming bell, but not a disaster.

It will be much worse if the virus has the ability to spread among people, because the bird flu is characterized by a very high lethality, and humanity still does not have immunity to it, ”the specialist emphasized.

The scientist explained that the insidiousness of influenza viruses lies in the way they mutate.

“Unlike the coronavirus, which changes links in its DNA, the flu is different.

Its genome consists of several fragments, viruses exchange them, and as a result, new strains arise,” Chumakov explained.

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The professor recalled that the bird flu virus has been a concern of the scientific community for the past fifteen years.

“One way or another, but in the end this virus will gain the ability to spread from person to person.

It is already capable of infecting a person, which means that one or two steps remain before it spreads among people, ”Chumakov said.

However, if necessary, the creation of a vaccine against bird flu will not cause any problems, the expert is sure.

“Now there is a huge industry that creates flu vaccines.

Every year, a variant of a cure is created for a newly emerging and circulating strain.

Most likely, it will not be very difficult to make a vaccine against bird flu, ”concluded Chumakov.