MOSCOW, December 1, Tatyana Pichugina In the UK, the first human infection with an influenza virus circulating among pigs was detected. Authorities are trying to find the source. In 2009, swine flu claimed almost 290 thousand lives.
What is known about the new swine flu
Recently, the British Health Protection Agency reported that in the north of Yorkshire, a patient with cold symptoms was diagnosed with the A(H1N2)v virus. The pathogen is not related to any of the flu strains spreading this winter. Pigs have related lines. This variant was assigned to clade 1b.1.1.
«Typically, a new virus arises when a pathogen jumps from animals to humans, or two strains recombine. Such pathogens have difficulty replicating, but there is always the possibility that they will adapt and become more infectious,» the British Science Media Center quotes John Edmunds, a professor at the Center for Mathematical Modeling. Infectious Diseases at the London School of Hygiene and Tropical Medicine.
Since 2005, only 50 cases of A(H1N2)v infection have been reported. In 2022 there were seven, including in the Netherlands. Only one person was hospitalized; the rest were mildly ill. The British patient has also already recovered.
“This is good news — the virus turned out to be not very pathogenic. However, it is important to know the age, health status of the patient, whether he belongs to some risk group for severe infection, whether he is susceptible to complications due to the flu. Or is he practically healthy and has recovered naturally,” — explains Andrew Kachpole from the research organization hVIVO.
The expert urged not to panic. According to him, such pathogens do not live long in humans.
“Concerns will arise if the persistence of transmission of the virus from person to person is established with certainty in a population that has not previously encountered it and has no immunity to it. There are no prerequisites for this yet,” Kachpole emphasized.
What the influenza A virus is capable of
The new strain was identified as a result of systematic monitoring. Scientists are now checking the chain of infections.
«All close contacts will be tested. If anyone has cold symptoms or tests positive, they will remain under medical supervision,» the British Health Protection Agency said in a statement.
Those with symptoms are advised not to have contact with others, especially those who are elderly or have health problems.
Experts note that influenza viruses are well controlled.
“Joint monitoring among humans and animals makes it possible to detect these types of infections. Without this, we would only learn about new viruses from severe cases or widespread disease,” says Kachpole.
“The fact that the virus was discovered in monitoring may indicate that it has been spreading in the population for some time. Contact tracing needs to be done,” adds Professor Edmunds.
According to Ed Hutchinson of the University of Glasgow, viruses are highly dependent on their hosts and rarely adapt. The causative agent of influenza type A differs precisely in that it infects different groups of animals, but even it replicates with difficulty. Typically, a virus that has passed from a pig to a person does not move on. Virologists call this a secondary infection.
“The type A influenza virus has special mechanisms for transferring to other biological species. In addition, human and animal strains can cross in one organism and produce hybrid offspring adapted for development in humans. Our immunity from previous influenza diseases or vaccinations does not recognize it «That's why it's important to track secondary infections,» Hutchinson says.
Is there a danger
In 2009, there was a swine flu pandemic in the world. 284 thousand people died.
The epidemic was caused by influenza A virus subtype H1N1(pdm09). Its genome included sections from the genomes of pathogens previously found in pigs, birds and humans. The name «swine flu» is no longer used for it. This strain has become seasonal and constantly circulates among people.
So, according to the National Influenza Center (St. Petersburg), in 2022-2023 more than two thousand genomes of influenza viruses were sequenced. Of these, 1723 belong to the H1N1(pdm09) subtype. For example, this week in Russia only seven cases were detected in four cities. In other countries of the world, 27.8 percent are caused by this subtype.
But the strain identified in the UK is unrelated to it. It belongs to the H1N2 subtype, which occurs only sporadically in humans. Scientists consider it unlikely that this pathogen will cause an epidemic.