Zika Virus, Where Does It Come From?

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Source : NEWSCOM/SIPA

Everything started back in the 40s. A research team in Uganda, lead by Alexander Haddow, was studying the yellow fever virus near Entebbe. In April 1950, the team isolates a new virus from a monkey used as a test animal in the Ziika forest.

The first human clinical case was described in 1954 in Nigeria. Then, in 1956, an experiment was conducted on a volunteer who got infected with the Zika virus through bites of infected mosquitoes. The subject developed a weak fever with a mild skin rash. The symptoms disappeared within a week. No more doubt, the Zika virus can infect human being via a mosquito bite.

The Zika virus was isolated in numerous species of Aedes mosquitoes in Africa and Malaysia. In 2007, the virus was identified in Micronesia, in what was the first large scale epidemic. Since then, the Zika virus has been considered as an emerging virus.

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Aedes aegypti Mosquitoes

During 2013, an outbreak was raging in French Polynesia. The virus rapidly spread  and was confirmed in the five archipelagos of French Polynesia which count roughly 270,000 inhabitants. Between October 2013 and March 2014, the number of infected persons is estimated at 28,000 individuals. 73 cases of Guillain-Barré syndrome were described during this epidemic. The Guillain-Barré syndrome is a rare affection that can cause muscle weakness and even paralysis. Sporadic cases of Zika virus disease were described throughout Oceania.

In Brazil, at the start of 2015, an increasing number of patients presenting symptoms similar to the Dengue virus disease were observed. This increase stroke the attention of Brazilian Public Health authorities. An infectious disease specialist evaluated some patients and laboratory results confirmed that the virus was not the Dengue nor the Chikunguya virus. In March 2015, the Zika virus was confirmed by the Carlos Chagas Institute. It was the first time that Zika virus disease was contracted in the Americas.

The virus strain isolated in Brazil is somewhat close to the Asian strains with similarities to the virus isolated in Oceania a few years ago. Some experts believe that the virus was imported into Brazil during the World Championship of pirogue (va’a) that was held in Brazil in August 2014. Four Oceanian countries where the virus is circulating were present at the Championship. To this day, it was estimated that about 1.5 million cases of Zika virus disease occurred in Brazil, which makes it the biggest Zika virus outbreak ever recorded. It is now spreading to other countries where the Aedes mosquitoes are present. The Zika virus is suspected to be linked to microcephaly touching the fœtus of infected mothers. According to the Brazil Health Minister, 4,783 suspects cases of microcephaly were described so far (February 2016). Active research is  ongoing to find if and how can the Zika virus be related to birth defects.

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