Published: Feb. 1, 2016
Dr. Misch

The Zika virus, discovered in 1947 in Africa, is related to the viruses that cause yellow fever, West Nile, dengue and chikunguna, and it is spread by bites of the mosquitos Aedes aegypti and, to a lesser extent, Aedes albopictus. In the past the virus was found principally in Africa, southeast Asia, and parts of the Pacific, but over the past several years and especially in the last 6-9 months it has grown “explosively” in the Americas. Brazil has been especially hard hit, and there is concern that the coming Olympics in Rio de Janeiro may cause further expansion of the virus’ territority.

Why is the outbreak of Zika virus serious?

For most people, the Zika virus presents little medical concern. Of healthy people who are infected, perhaps 80 percent have no symptoms. The remaining 20 percent may experience mild symptoms of headache, rash, red eyes and joint pain. As is the case with other viral infections, a rare complication is Guillain-Barre Syndrome, which may cause total paralysis.

The greatest concern is evidence suggesting that pregnant women infected with the virus, especially during the first trimestser, may give birth to children with microcephaly—abnormally small heads—with associated failure of normal brain development. While cause and effect has not been definitively proven, since November Brazil has reported 4,180 causes of babies born with microcephaly whereas in 2014, prior to the current outbreak, only 146 such babies were born. 

Currently, there is no treatment or cure for Zika virus infection, and it appears that an effective vaccine is at least three years away.

Will the Zika virus affect the United States?

Thus far there have been over 30 confirmed cases of Zika virus infection in the United States, but all have been related to travel outside the country. While it is likely that the virus will become localized in the United States before long, for a variety of reasons experts believe the virus will be restricted and that the U.S. will not experience the explosive spread seen elsewhere.

How can you protect yourself against the Zika virus?

The aedes aegypti mosquito is an aggressive biter that prefers daytime to dusk and indoors to outdoors. The key is basic mosquito protection that involves using an EPA-approved mosquito repellent over sunscreen, thick long pants and long-sleeved shirts, keeping screens on windows and doors, and sleeping in air-conditioned, screened rooms without open windows. These measures are also effective against the West Nile virus, which is a significant threat in Colorado in the summer months. 

The Centers for Disease Control and Prevention has issued travel advisories for women who are pregnant or are planning to become pregnant for many countries in South and Central America as well as Mexico, Puerto Rico, Saint Martin and the U.S. Virgin Islands. Pregnant women or those considering pregnancy should carefully consider travel plans.  For students and others, the upcoming spring and summer breaks, as well as travel abroad, may represent periods of increased risk.  Women planning to travel to the affected areas are urged to use effective birth control methods.  For more information on travel advisories, see below.

What else is being done to control the Zika virus?

While work continues on the development of a vaccine, health officials are implementing traditional mosquito control techniques such as spraying pesticides and emptying standing water receptacles. Local homeowners and others are encouraged to similarly eliminate standing water (e.g., in outdoor buckets, flowerpots and even very small sources of water) as well as remove outdoor trash to which the Zika virus is attracted. These measures will become more important in the summer months and if the virus spreads locally or nationally in this country.

Another approach being tested with some success is the introduction of genetically modified Aedes aegypti male mosquitos that inhibit viral spread by passing along a gene that makes male offspring die. Early field trials of this approach in Brazil have resulted in elimination of more than 90 percent of the targeted mosquitos.

Where can I get more information?

Additional information can be obtained through the Centers for Disease Control and Prevention (, CU-Boulder Study Abroad, International Student and Scholar Services and Wardenburg Health Services.

Donald A. Misch, M.D.
Senior Assistant Vice Chancellor for Health and Wellness, and Executive Director of Wardenburg Health Services