Zika virus, first identified in 1947 in Uganda, had been thought to produce a rare and mild disease until it suddenly emerged in Brazil in 2015 and spread explosively through South America, Central America, and the Caribbean. The virus arrived in the United States in the summer of 2016. Zika virus is transmitted primarily by mosquitoes that thrive in tropical climates and urban areas. The virus can cause Zika virus disease. Zika virus can cause a serious birth defect known as microcephaly. Zika virus can also cause a neurologic condition in adults known as Guillain-Barre syndrome that results in muscle weakness or even paralysis in the worst cases. Two types of Aedes mosquitoes are capable of transmitting Zika virus – Aedes aegypti and Aedes albopictus. Aedes aegypti thought to be present only in 12 states in southern coastal areas of the United States, Aedes aegypti has now been found in about 30 states.
In Brazil, an explosive epidemic of a condition known as microcephaly has been correlated with the outbreak of Zika virus. Microcephaly can be caused by a number of genetic and environmental factors, including Down syndrome and fetal exposure to a variety of toxins. However, the number of microcephaly cases in Brazil since the Zika virus outbreak began is about twenty times higher than normally would be expected. It is estimated that approximately 500,000 cases of Zika virus infection have occurred in Brazil, although exact numbers are not known because of the difficulty in keeping track of the large number of cases and the fact that many infections go unnoticed. After Brazil, Columbia has been the most affected country with around 20,000 estimated cases. As of Oct. 26, 2016, there have been 139 laboratory confirmed cases acquired locally in FloridaZika Virus in the United States
As of Oct. 26, 2016, Zika virus infection has been acquired by nearly 4,000 people in the United States as a result of travel to areas where Zika virus infected mosquitoes are present. Travel-associated cases have been reported in all states except Alaska. The greatest number of cases is in New York and Florida with around 1,600 cases between them, followed by California and Texas. Of these cases, 33 were sexually transmitted. Approximately 950 pregnant women have laboratory evidence of Zika virus infection, and there have been more than 20 cases of birth defects or pregnancy losses tied to Zika infection.