Genetics: the zika virus started to cause microcephaly only in 2013

© AP Photo / LM OteroКомары vector of zika virusGenetics: the zika virus started to cause microcephaly only in 2013© AP Photo / LM Otero

The zika virus was rather harmless for humans until 2013, when his DNA did not appear a single mutation and it has not acquired the ability to penetrate into the fetus and infect the stem cells of the brain, according to a paper published in the journal Science.

«Zika virus was first discovered in Uganda in 1947 and until recently it remained almost forgotten tropical wonder. Evolutionary analysis showed that in 2013, during an outbreak in French Polynesia, he has acquired a single mutation that made it more infectious to humans and hazardous to the fetus in the womb» — written by Jichen Xu (Zhiheng Xu) from the Institute of brain problems in Beijing (China) and his colleagues.

This virus is spread by mosquitoes, causing fever zika leads to the development of symptoms similar to dengue fever, scabies and joint pain. According to current who statistics, about four out of five infected adults not experiencing serious ailments, and in General, this fever rarely leads to death of the patient.

On the other hand, as shown by the monitoring of patients in Brazil, women who had had fever Zeke during pregnancy, often give birth to children with severe defects – microcephaly and other deformities of the skull and skeleton. For this reason, the government of El Salvador has urged women to postpone pregnancy for two years until the doctors can not cope with the virus.

In early March of last year, neuroscientists from the United States stated that the reason for the development of microcephaly in a child when infected pregnant women with the virus zika is that the particles of the pathogen deep into stem cells, «blank» the future of the nervous tissue, causing their mass death. In total, the zika virus has affected more than two thousand children born in the last two years in Brazil and other countries of the New world.

Xu and his colleagues wondered why Zeke virus, is widely distributed in tropical regions of Asia and Africa, has not caused such epidemics and tragic side effects before. To answer this question, scientists have deciphered and compared the genomes of different versions of the zika virus, which caused outbreaks of the same fever in different parts of Africa and Asia in the last two decades and tested their effects on newborn mice.

Much to the surprise of scientists, new and old strains of the virus affected rodents completely different way – the «new» version of the virus killed all the mice into their brains, while the old strain Physics destroyed only 16% of the animals.

Having such an unusual outcome, the scientists compared the genomes of viruses and found that such differences in activity of the virus was caused by a mutation only in a single «letter» DNA, named S139N. She changed jobs protein in which the pathogen attaches to the surface of infected cells, «teaching» him to penetrate the future neurons of the cerebral cortex.

This mutation, as scientists have discovered, for the first time appeared among the viruses isolated from patients infected with zika fever in French Polynesia in may 2013. From there the bearers, apparently, came to the territory of Brazil or other countries in South America, where a new, more contagious and deadly version of the virus began to rapidly spread, causing an epidemic of 2015.

Now the scientists plan to study other samples of the virus from other parts of Asia, Africa and America, which they hope will help them to map the spread of a dangerous version of fever zika and focus efforts to combat it in these regions.