A 4-month-old baby born with microcephaly is held by his mother in front of their house in Olinda
(Copyright Reuters 2017)
CHICAGO – A single genetic change that occurred in 2013 can explain how Zika acquired the possibility of attacks of fetal nerve cells, causing a severe congenital anomaly in babies whose mothers were during pregnancy infected, Chinese and AMERICAN researchers reported on Thursday.
Scientists have proposed many theories about why Zika, a mosquito-borne virus that was associated with only mild symptoms, since the discovery in 1947, all of a sudden could be associated with thousands of cases of birth defect known as microcephaly, as it was in Brazil in 2015.
That outbreak prompted the World Health Organization to declare Zika a public health crisis in 2016, and a scientific quest to determine whether Zika may cause microcephaly, a condition that is characterized by small size of the head.
A number of teams have already traced the virus circulating in Brazil and elsewhere in South America to a strain of Zika was quite in circulation in Southeast Asia for decades.
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In the new study, published in Science, Yuan Ling from the Chinese Academy of Sciences and colleagues compared the genetic changes in the samples of the South American virus isolated in 2010 in Cambodia.
They made seven sample viruses, each with a genetic difference between the Cambodian strain, and these have been tested in the brains of fetal mice. Although the viruses caused a certain degree of damage in all, which are infected with a virus that has a single mutation in a structural protein called prM developed severe microcephaly. That tension also proved to be more lethal to fetal brain cells.
The team estimates that the genetic change occurred in May 2013, just before the outbreak of the French Polynesian Zika in that the first cases of microcephaly and the Guillain-Barré, a rare neurological disorder, were noted.
“Our findings offer an explanation for the unexpected, the causal relationship of Zika to microcephaly, and will help to understand how Zika has evolved from an innocent mosquito-borne virus of an innate pathogen with a global impact,” Yuan and colleagues wrote.
A study author, Dr. Pei-Shi Yong of the University of Texas Medical Branch in Galveston, Texas, said other changes also led to the explosive epidemic, as he and others reported in May in the journal Nature that improved Zika the ability to infect Aedes aegypti mosquitoes that have the virus.
In November last year, WHO pronounced Zika no longer an international emergency, but stressed that the virus found in at least 60 countries, the spread of where mosquitoes Zika.