Zika landed in Brazil 2 years before it was detected

They used samples taken Zika cases across Brazil and looked for mutations in the genetic sequence. For infants and children who contract Zika through mosquitoes, the disease typically is mild just as it is for adults, and treatment involves supportive care, according to the CDC.

It is unlikely that the disease would spread in the United States as fast as it has in Latin American because of the widespread availability of air-conditioning, helping people stay indoors longer in the summer, the report's authors say. The small differences between each sample allowed the scientists to construct Zika's family tree and estimate when their common ancestor arrived in Brazil. The similarity of these indicates that the disease was most likely introduced by one person, but dates this to sometime in 2013.

"Since January 2016, 27 cases have been routinely tested for Chikungunya virus, dengue fever and Zika virus". No mosquitoes carrying to virus have been found in Southern Nevada.

That's a good thing since Aedes aegypti kills more people than any other vector species on earth, Krummenacher said Wednesday.

The virus has since spread to 34 countries or territories. Some northeastern Brazilian towns such as Pernambuco and Paraiba have more than 10 cases of microcephaly per 10,000 births.

While scientists are working to understand the virus, its transmission, and the effect on those infected, researchers at Florida State University believe they have made an important breakthrough.

Symptoms usually appear following an incubation period of three to 12 days after the bite of an infected mosquito, lasting between four to seven days, and are self-limiting. By comparison, Brazil reported the country's first Zika case in May 2015.

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Brazil had thought athletes or spectators brought the virus with them during the 2014 World Cup Soccer tournament.

"The genome sequences can tell us where the outbreak has come from... and how it's been spreading", says Oliver Pybus, an evolutionary biologist at the University of Oxford, who led the study.

"However, the modeling of other Zika outbreaks, and also the highly-related Dengue outbreaks, suggest that this is not unusual", Hibberd said.

Cases of Zika have reached epidemic levels in that country, most of South America, throughout Central America, parts of Mexico and much of the Caribbean.

First discovered in Uganda in 1947, the Zika virus wasn't thought to pose major health risks until past year, when it became clear that it posed potentially devastating threats to pregnant women. An assessment of that data suggests that suspected microcephaly cases are "best predicted by Zika virus incidence during week 17 of pregnancy, on average, or week 14 for suspected severe microcephaly cases", the researchers wrote.

Investigators are trying to determine if there is a link between the virus and an increase in birth defects, the Health District said. And a pregnant woman from Switzerland who got married in the Dominican Republic - which shares an island with Haiti - in August 2013, gave birth to a boy with microcephaly, normally a very rare condition.