The new flu
Swine flu virus called a threat of a new pandemic
Svetlana Yastrebova, N+1
Since 2016, domestic pigs in China have been dominated by the influenza virus, the genome of which combines the characteristics of the H1N1 swine flu virus strains that caused the 2009 pandemic, and the North American reassortant strain (combining the genes of several virus varieties at once), according to the Proceedings of the National Academy of Sciences (Sun et al., Prevent Eurasian avian-like H1N1 swine influenza virus with 2009 pandemic viral genes facilitating human infection). Laboratory studies have shown that it very easily colonizes the epithelial cells of the human respiratory tract, and more than 10 percent of pig farm workers have antibodies to it. All this indicates that the new swine flu virus (its strain was named G4 EA H1N1) may cause a new pandemic.
In 2009-2010, there was a pandemic of influenza caused by the A/H1N1 virus, strain H1N1pdm2009. The first cases of the disease were recorded in the USA and In Mexico in April 2009, and then within a few months the infection spread around the world. According to the US Centers for Disease Control and Prevention, 151700-575400 people died as a result in the first year of the virus circulation.
A/H1N1 turned out to be particularly contagious and dangerous, since it appeared as a result of reassortment — mixing the genetic material of several viruses. A/H1N1 is a "cross between" influenza viruses that infect pigs (that's why the flu was called swine), birds and humans. When this happens, a new virus often gains the ability to infect those species that were previously immune to it. Therefore, it is worth studying which viruses infect animals with which a person often comes into contact — agricultural, domestic pets, those who often become prey to hunters, and so on. It is their pathogens that are most likely to become human due to reassortment, too.
Therefore, researchers from several scientific institutions in China, led by Jinhua Liu from the Chinese Agricultural University, checked which influenza viruses circulated among pigs on Chinese farms in the 10 most "piggy" provinces in 2011-2018, and determined how their occurrence changed over the years. To do this, scientists took nasal swabs from animals killed for meat (29918 samples), and also made homogenate from the lungs of pigs with pronounced signs of respiratory infection (1016 samples). Viruses were detected by polymerase chain reaction: we looked primarily at the genes of hemagglutinins (H in the name of the influenza virus) and neuraminidases (N in the name of the influenza virus). Their sequences were compared with those already known for other strains.
The genome of one of the 179 virus varieties found, the closest in structure of the H and N genes to the H1N1pdm2009 strain, was sequenced completely. Cultures of human tracheal epithelial cells were used to test how easily it binds to various versions of the sialoglycoprotein SAa2,6Gal — one of the key molecules for infection with influenza viruses. In addition, the authors analyzed data from immunological tests of 338 employees of 15 pig farms, during which in 2016-2018 the presence of antibodies to certain strains of influenza viruses was detected. They were compared with the results of similar tests of 230 people not involved in animal husbandry.
It turned out that in 2016, a new strain of the H1N1 influenza virus, which the authors called G4 EA H1N1, began to spread rapidly among Chinese pigs, and since then it has been more common than others. Apparently, G4 EA H1N1 appeared as a result of reassortment of Eurasian and American A/H1N1 strains. In experiments with cell cultures, it preferably bound to the "human" version of the sialoglycoprotein SAa2,6Gal. An additional series of experiments on ferrets (these animals are very often used to evaluate vaccines and medicines against influenza) showed that G4 EA H1N1 is easily transmitted from one animal to another.
In pig farm workers, antibodies to the virus were detected in 10.4 percent of cases, in people not related to agriculture, in 4.4 percent of cases. The effect persisted even after the possible cross-reactivity with H1N1pdm2009 was taken into account (that is, the variant when the antibodies were to the strain that caused the pandemic in 2009, and not to the new virus). All this (proximity to humans, a large proportion of people with antibodies to the strain, the ease of its binding to the desired glycoprotein and transmission from one individual to another) indicates that G4 EA H1N1 may cause a new pandemic in the coming years. Therefore, the authors point to the need to begin periodic inspections of pig farm workers, as well as pigs themselves, for infections associated with influenza viruses as soon as possible.
In 2016, American scientists found out that the severity of the flu caused by a certain strain of the virus can be estimated by the patient's year of birth. It depends on what types of virus a person encountered in childhood, and such information can be obtained by knowing their prevalence in a particular season. Influenza viruses within the same group have similar neuraminidase glycoproteins, and if the immune system has already encountered neuraminidases of a particular group, it will most likely be easier for it to fight off viruses with glycoproteins from the same group.
Portal "Eternal youth" http://vechnayamolodost.ru