Ebola mutates

Could a new mutation of the Ebola virus make it more dangerous?

Evgenia Efimova, Vesti

The scale of the Ebola epidemic, which began in 2013 and engulfed West Africa, still remains, in a sense, a mystery to scientists. For the simple reason that more than 600 people have never fallen ill in previous Ebola outbreaks. But during the last epidemic in Liberia, Sierra Leone and Guinea, there were already more than 28,000 cases before it was brought under control.

In part, the large number of infected people is explained by the fact that the virus appeared in large cities, which made it more difficult to eradicate it than in more isolated rural areas (where it originated earlier). Of course, the weak health infrastructure of the countries, as well as other environmental factors also played a role.

But two documents have recently appeared that may somewhat clarify the reason for such a large-scale spread of fever. They show that just three months after Ebola "gained momentum" and has already begun to become a full-scale epidemic, the virus itself has undergone mutation. In turn, this made the virus "more suitable for humans" than, as is assumed, for its original host – one of the bat species.

"The virus has never been transmitted so often from person to person before, so there were a lot of mutations," says evolutionary geneticist Pardis Sabeti from Harvard University. Sabeti is a co-author of one of the articles.

The researcher emphasizes that her team has only "indirect data" about the time of mutation and the outbreak of the epidemic. Meanwhile, Sabeti's research team and another independent team that published a second scientific paper on the same topic have accumulated "convincing evidence." The latter, according to scientists, for the first time signal that the mutation of the virus has made it more contagious to human cells.

The results of the study increase the likelihood that the mutation directly affected the increase in the number of cases of transmission of the virus, and consequently, the aggravation of the situation as a whole. "We should neither panic nor calm ourselves down. But any possibility that any of the mutations could lead to serious consequences should be considered," says Sabeti.

Virologists feared from the very beginning that a large number of infected people could give the virus "strength" to adapt to humans. Ebola, avian influenza and other diseases that were originally characteristic only of animals, if deadly to humans, are not very effective in spreading (the contagiousness and lethality of the virus cannot go hand in hand in the case of one strain, which, of course, is good for humanity).

However, many experts at the beginning of the epidemic in West Africa have already warned: the more people become infected with the pathogen, the more likely it will evolve and become easier to spread among people.

It seems that's exactly what happened. The epidemic began in Guinea and then spread to Sierra Leone, when there were only about 100 cases. During this period, the virus acquired a mutation called A82V, which is responsible for the surface of the main protein that binds to the victim's cells. The researchers analyzed the genetic code of almost 2,000 samples of the Ebola virus to make such a conclusion.

Jeremy Luban from the University of Massachusetts, in an interview with the BBC, reports that "mutations make the virus more contagious." "The mutation appeared at the beginning of the epidemic, about three or four months after it started," he says.

According to experts, this is the first major epidemic in which the genes of a pathogen have been studied almost in real time as the disease spreads. The analysis also showed that the A82V mutation was preserved in subsequent viral particles. And the appearance of this mutation coincided with the intensification of the epidemic, as soon as the virus later manifested itself with renewed vigor in Guinea.

So, both research groups report at once that the A82V mutation allowed the Ebola virus to infect cells of humans and other primates four times more effectively than the unchanged virus.

However, the connection between mutations and the subsequent intensification of the epidemic may also be a common coincidence. Researchers cannot officially prove that mutations have increased the evolutionary fitness of the virus without testing on experimental animals. However, in the future they want to test their hypothesis in a high-pressure laboratory.

But Luban believes that all the evidence already collected indicates that the mutation contributed to the aggravation of the epidemic.

The mutation could also make the virus more dangerous, experts say. Luban's research team analyzed 200 cases for which viral genes and data on the course of the disease itself were known. People with A82V had a large amount of the virus in their blood and were almost three times more likely to die.

But the good news in this whole story is that the A82V mutation disappeared when the epidemic ended.

However, according to scientist Jonathan Ball from the University of Nottingham, since the A82V mutation appeared at the very beginning of the epidemic, this means that it or similar ones with similar dangerous properties may occur next time. In this regard, it is necessary to calculate all the risks in advance and respond quickly to any cases of the disease.

Both scientific papers are published in the scientific publication Cell (first and second).

We should add that it was recently reported that Russia and Guinea announced the start of trials of an Ebola vaccine.

Portal "Eternal youth" http://vechnayamolodost.ru 07.11.2016