Two steps away from the super virus
Scientists: avian flu will turn into a "super virus" in just two mutations
Avian influenza H7N9 will turn into a super-contagious virus capable of killing people and causing large-scale epidemics after acquiring only two mutations, scientists say in an article published in the journal PLoS Pathogens (de Vries et al., Three mutations switch H7N9 influenza to human-type receptor specificity).
"We did not create these viruses and did not check whether they could be transmitted by airborne droplets in the presence of those mutations that we discovered. It is possible that these mutations, which change how the virus interacts with the receptors of human cells, will be enough for them to acquire such an ability, but it is also possible that other mutations will be required for this," said James Poulson from the Scripps Institute in La Jolla (in the press-the release of Influenza Virus Can Overcome Potentially Crippling Mutations – VM).
Outbreaks of avian (H5N1) and swine (H3N2) influenza in the late 2000s caused serious concerns among virologists and doctors who claimed the threat of an influenza pandemic similar in scale to the Spanish flu pandemic in 1918, which claimed millions of lives. However, as long as these viruses cannot spread by the traditional airborne droplet route and be transmitted from person to person, there is no threat of a pandemic. These types of flu are infected only by those people who are in close contact with birds or pigs.
In the spring of 2013, there were outbreaks of infection in southern China caused by a previously unknown strain of H7N9 avian influenza. During the first half of the year, more than 130 people were infected with it, about a third of whom died from exhaustion or complications. In March of this year, Chinese scientists discovered that this virus can sometimes be transmitted from person to person, which forced doctors to pay close attention to it.
Poulson and his colleagues analyzed new samples of H7N9 obtained from hospitals in Hong Kong and other cities in southeastern China, and found that the virus had mutated and acquired several new changes in the structure of the shell. This forced scientists to re-analyze how close the new H7N9 strains are to becoming a "super virus".
The fact is that back in 2011, well-known virologists Yoshihiro Kawaoka and Ron Fouche showed, experimenting on ferrets, that most of the varieties of "bird flu" (in fact, they studied only one strain, H5N1 – VM) can learn to spread through the air and kill a large number of people by acquiring only three mutations. These experiments caused a wide public outcry and scientists were actually banned from conducting experiments to "improve" the flu virus in the United States and European countries.
Nature, as the analysis of Poulson and his colleagues showed, does not take into account such prohibitions and does not stand still – now H7N9 is no longer three, but two steps away from becoming a "supervirus", having acquired a mutation that allows it to attach to the walls of human cells.
To complete the transformation, the avian influenza virus needs only two changes in one of its shell proteins, hemagglutinin, which it uses to attach to special "tails" on the cell surface and penetrate inside it.
Figure from the article in PLoS Pathogens – VM.
As scientists emphasize, they came to such conclusions during experiments on fragments of the virus shell, and not after experiments on mammals, which does not allow us to be 100% sure that these two mutations are really enough to create a "super virus".
For further study of this virus, according to Poulson and his colleagues, experiments on experimental animals are needed, currently banned in the United States due to fears that the results of such experiments will help terrorists develop biological weapons. Scientists hope that this problem can be solved in other countries where there are no such prohibitions, for example, in China or in other Asian countries.
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21.06.2017