The Zika Epidemic
*Global map of the predicted distribution of Aedes aegypti, one of the types of mosquitoes that spread Zika. Credit: Elife Sciences.org
Although humans fear attacks by sharks, lions and snakes, on average human deaths from these creatures account for 10,000 to 50,000 deaths annually. The tiny mosquito, by contrast, accounts for 475,000 deaths a year, primarily through malaria.
Mosquitoes, specifically Aedes aegypti and Aedes albopictus, also carry a variety of viruses of the genus Flaviviridae that include dengue, yellow fever, West Nile, and Zika viruses, among about 70 others. Originally confined to Africa and Asia, these mosquitoes have now spread to tropical and subtropical areas throughout the globe, including regions in the United States.
In recent years, accompanying the spread of the mosquitoes, there have been alarming outbreaks of dengue fever in Singapore, Indonesia, Japan, and Hawaii -- places where dengue, while a public health issue for many years in Asia, was previously not a major threat. In addition, and more troubling, there was an outbreak of Zika infection in Brazil in late 2015, accompanied by a remarkable increase in the incidence of microcephaly, a severe deformation of the skull in newborn children accompanied by possible mental retardation, vision problems, and Guillan-Barre Syndrome paralysis. In Brazil alone there was an increase of microcephaly cases to about 4,000 by year end. There are now reports of Zika transmission to humans in a number of other countries in Central- and South America and the Caribbean, and of Zika-infected travelers carrying Zika to the U.S. and Europe. There also have been reports of sexual transmission of Zika in the United States and elsewhere, an occurrence unknown to other flaviviruses, and a concern that Zika may reside in an infected person, unrecognized, for many years.
The Pan American Health Organization predicts that active Zika virus transmission will eventually spread to every country in the Western Hemisphere where the Aedes aegypti mosquito is found, excluding only Canada and continental Chile.