Over 60% of the victims of Ebola died in West Africa in 2014, contracted the virus thanks to a mysterious group of "super vectors" of Ebola, whose population is only 3% of the total number of infected, according to a paper published in the journal PNAS
"Now we understand that the role of the infection super-vector is very much underestimated. All calculations on the scale of the epidemic were based on hospital data, but in fact people died at home, played a more prominent role in the epidemic spreading than its victims in hospitals. We were able to unravel the chain of transmission of the infection and to go to a few large super-vectors," said Benjamin Dalziel from Oregon State University in Corvallis (USA).
According to the latest WHO data, in three West African States since February 2014, 24 people contracted Ebola fever, 9, 6 thousand died. In Liberia, from Ebola died more than 4 thousand people. In March 2015, the number of victims of Ebola exceeded the threshold of 9 thousand people. Beginning from the middle of-2015, the number of new infections decreased significantly. That suggests that the epidemic has gone on recession.
Dalziel, and his colleagues found that approximately 60% of the deaths from Ebola fever during this epidemic could have been prevented if scientists knew about the existence of the so-called "super- carries " – a special group of patients that had contracted a lot of other people because of a set of circumstances, their social status or local customs that contributed to the spread of infection.
Examples of such "super-carries" has already been in the past: for example, during the SARS outbreak in China in 2003, one of the doctors who contracted SARS transmit the disease to dozens of their relatives at a wedding and was the original cause of its spreading to 34 other countries. Even more well-known but nearly forgotten example is Typhoid Mary, a healthy carrier of typhoid fever, had infected about 50 people before she was figured out and isolated.
In the case of Ebola, the number of such people, as scientists note, would be measured not by units but by tens or even hundreds. Analyzing the data that was collected by the representatives of the International Red Cross in rural areas of Liberia and Sierra Leone at the burial of victims of Ebola, scientists have noticed a big bias in favor of primary infection – among the first victims of Ebola who died in the villages almost simultaneously, was in most cases significantly higher than the number of secondary infections.
Such peculiarity, as the researchers note, can be explained by the fact that the first victims of Ebola has contracted it from a common vector of infection, which acts, judging by the lack of visible differences in the course of primary infection in different villages in the same way.
So far the only clue about their identity is the age of these "super-carries". Dalziel and his colleagues’ calculations suggest that most of them are either children or the elderly. According to scientists, such Ebola victims could involuntarily contribute to its spreading, as their relatives and friends could take care of them, and the disease could develop in their body much faster.
The role of this mysterious group of people, representatives of which biologists expect to find, only grew, and it remained extremely high even after the epidemic has peaked and went into decline due to the measures undertaken by African Governments, WHO and the medical volunteers. This means that the measures were aimed in the wrong direction – it was necessary to deal with "super-carriers" and not isolated cases of the infection which they caused and which fell into the hospital.
As scientists noted, this mode virus spread cannot be explained only by the fact that burial rituals in these West African countries contributed to the massive infection with fever. The search of other factors that drove the Ebola epidemic is extremely important, since their timely detection in the past has helped to save tens of thousands of lives carried out by similar "super-carriers".