2020 is destined to be an extraordinary year, the impact of African swine fever has not yet gone far, the new crown of pneumonia began to spread again. Recently, a paper published in the Proceedings of the National Academy of Sciences referred to a new type of swine flu virus, causing global concern, for a time, “a new swine flu virus may trigger a pandemic” the idea spread.
Clearly, many people are still worried about the 2009 outbreak of the H1N1 influenza virus, which the paper calls similar to the 2009 H1N1 virus, raising fears of another pandemic.
Is this flu virus really so powerful? Has the virus spread among pigs? Is it a big impact on the pig industry? Will there be a human heirloom? …… Too many questions need to be answered.
“Hybrid” of three different viruses
For many years, Liu Jinhua, a co-author of the paper and a professor at the School of Animal Medicine at China Agricultural University, has been working on animal flu.
Since 2011, Liu Jinhua’s team has collected pig swabs from pig farms and slaughterhouses in more than 10 provinces and cities across the country. In 2018, 30,934 copies were collected and 179 strains of swine flu were isolated, most of them G4 genotype Eurasian avian H1N1 influenza virus (hereinafter referred to as G4 virus). The G4 virus is the new swine flu virus that has attracted much attention.
“Mutation and recombination are the most basic characteristics of influenza viruses. Because each influenza virus contains eight gene fragments, the eight fragments are independent and, when infected with a cell together, it is easy to exchange gene fragments and recombine several new virus particles. Liu Jinhua told China Science Daily.
“The G4 virus is of concern because it is a ‘hybrid’ of three known viruses, combining the Eurasian avian influenza virus, the Influenza A(H1N1) virus and another swine influenza virus.” Liu Jinhua said.
“This is very similar to the 2009 outbreak of influenza A(H1N1) virus in countries such as Mexico, the United States and Canada, and also has ‘hybrid’ characteristics. The human, pig and poultry genomes, which were circulating in 2009, were combined to form a pandemic. Yang Zhanqiu, a professor at the Institute of Medical Virology at Wuhan University’s School of Basic Medicine, told China Science Daily.
According to Liu Jinhua’s team, the G4 virus is not an emerging influenza virus, first detected in samples in 2013, and the number of swine infections with G4 virus esnited rapidly in 2016, which has become “mainstream” in the swine flu virus.
However, he stressed that the team sampled data before 2018. After the occurrence of African swine fever in 2018, the impact on China’s aquaculture industry has been great, the production model of the whole pig industry has changed dramatically, many large farms began to attach great importance to biosecurity, the current situation is not the same as before 2018.
“Pig-to-man” to “human-to-man” is not easy
Swine flu is a respiratory disease in pigs. But why does a disease belonging to a pig have anything to do with it?
“In fact, people, chickens, pigs, etc. can be infected with influenza viruses, and because of the influenza virus’s strong ‘social’ ability, the influenza virus eschews between these species and creates new viruses. And once the swine flu virus and the human influenza virus recombination, it can be infected with the possibility of human. Yang Zhanqiu explained.
According to the contents of the paper, Liu Jinhua’s team conducted serum testing on pig farmers, and the seropositive rate was about 10.4%. “However, this does not mean that these positive samples were infected with the G4 virus, because the tests were affected by other interference factors, such as the subject having been vaccinated or having had influenza A(H1N1), and the testing of antibodies would also be positive, which is difficult to rule out.” Liu Jinhua said.
The above data only show that the G4 virus may have infected humans, but the results based on serological surveys do not indicate that the G4 virus has become endemic between pigs and people. Yang Zhanqiu pointed out that the most effective way is to have virology evidence.
Unfortunately, because influenza stays in humans for a short time, when the onset of the disease for nasal swabs and throat swabs to separate into the virus, once missed the onset stage, it is difficult to isolate the virus, so no effective virological evidence is currently available.
In turn, the researchers used ferrets, commonly used in human influenza viruses, as a breakthrough in exploring infection and transmission paths.
The results show that the G4 virus is highly pathogenic and transmitted in ferrets.
“Although we don’t have any human-to-human cases, combined with the ferret model and the high genetic similarity within the G4 virus and the 2009 outbreak of influenza virus, the possibility of a G4 virus pandemic is present and we should pay enough attention.” Liu Jinhua said.
According to Peng Daxin, a professor at Yangzhou University’s School of Veterinary Medicine, the paper makes sense, and the G4 virus deserves attention, but there is no need to panic at all. Although information suggests that the G4 virus does have all the characteristics of an infected person, it does not necessarily lead to effective transmission in the human body.
“In fact, most swine flu viruses don’t spread in humans. Not a virus after recombination will appear to adapt to human virus, need to go through a series of ‘screening’ and ‘mutation’, recombinant virus does have an infection risk, but to the real infection there is a certain probability, not the risk immediately into the actual situation, recombinant virus to adapt to the human body is not easy. Peng Daxin told China Science Daily.
Just as the previous “hot” H5 subtype of highly pathogenic avian influenza virus has been predicted around the world as the next pandemic. Despite concerns about the rise and fall, there have been a small number of cases of infection, but ultimately failed to become the “main character” of human influenza.
Strengthen monitoring and research and development of vaccine “two-handed grasp”
Because of the outbreak of new crown pneumonia, the global economy has been significantly affected, if there is another large-scale infectious disease at this time, will make the situation even more serious, making people’s lives worse. “Breaking down” the source of the G4 virus’s spread has become a priority.
Because the influenza virus is not resistant to heat, so influenza usually occurs in the winter and spring festival, is not the influenza virus epidemic season, Yang Zhanqiu believes that we still have time to do a good job of response.
“Systematic surveillance of swine flu viruses should be strengthened and virological investigations should be done, which is essential for early warning and the prevention of the next potential pandemic. Next, we will continue to pay attention to the virus mutation, prevention of the disease before it occurs. Liu Jinhua said.
In addition, Peng Daxin suggested that a reserve for vaccine candidates for the virus should be established.
“The current use of reverse genetic technology to develop influenza virus vaccine is a very mature technology, screening to the right vaccine candidate strain can quickly develop targeted vaccines. Once the G4 virus is detected in the population, effective vaccines can be quickly provided to kill the virus in the cradle. For G4 virus infection in pigs, the same method can be used to upgrade the vaccine for swine flu prevention and control. “
There’s nothing wrong with preventing a person with a G4 virus, but experts say there’s no need to worry about a person with A4 virus infection.
“The death rate from the 2009 outbreak of influenza A(H1N1) was not very high, at around 1%. The G4 virus only acts on the upper respiratory tract and does not invade the lungs, and the fatality rate is very low, and the current level of new coronary pneumonia is not a level. Yang Zhanqiu said.
As for the pig industry, Mr Pang thinks it will have little impact. “In the pig industry, influenza is not a major disease of concern, compared with african swine fever and other major, high-risk infectious diseases, influenza is a ‘small role’, its morbidity and mortality rate is not high. Healthy pigs have a certain resistance to this type of influenza virus, and human infection with influenza virus, relying on their own resistance can be ‘responded to’, in the absence of other pathogen infections, often one-off. “
Despite the potential for an influenza pandemic, the surveillance network of influenza in our country is well established. “The flu has its own regularity and doesn’t suddenly appear like the new coronavirus, catching humans off guard.” Yang Zhanqiu said.