What Are We Doing to Get Ready for Zika in the United States? Medscape Asks and the CDC Answers

CDC Division of Vector-Borne Diseases; CDC Division of Congenital Developmental Disorders

May 04, 2016

Editorial Collaboration

Medscape &

Medscape: Are we correct in assuming that as the weather in the continental United States warms up, we can expect to see local Zika transmission in any or all states? What predictions can you share with medical professionals about which states might be affected or the number of cases that can be expected?

Many areas in the United States have the type of mosquitoes that can become infected with and spread Zika, chikungunya, and dengue viruses. Recent outbreaks of chikungunya and dengue, which are spread by the same type of mosquito, in the continental United States have been relatively small and limited to a small area. CDC is not able to predict whether Zika virus will spread in the continental United States. However, areas with past outbreaks of chikungunya and dengue are considered at higher risk for Zika. These include US territories like Puerto Rico, the US Virgin Islands, and Guam. Local outbreaks have also been reported in parts of Hawaii, Florida, and Texas.

For Aedes aegypti or Aedes albopictus mosquitoes to cause an outbreak in the continental United States, all of the following must happen:

  • People infected with a virus (eg, Zika, dengue, or chikungunya) must enter the United States.

  • An Aedes aegypti or Aedes albopictus mosquito in the United States bites an infected person during the period of time when the virus is in the person's blood, typically only through the first week of infection.

  • The infected mosquito lives long enough for the virus to multiply and for the mosquito to bite another person.

  • To infect enough people and for mosquitoes to start an outbreak, the cycle would need to continue over time.

CDC has maps that show CDC's best estimate of the potential range of Aedes aegypti and Aedes albopictus in the United States. The maps are not meant to represent the risk for disease.

Medscape: What entities are responsible for mosquito control in the United States? Are there plans for any enhanced mosquito control measures in particular states?

Mosquito control in the United States

  • Mosquito control is licensed, prioritized, funded, implemented, and overseen at the local or state level.

  • The size of a mosquito control program can vary within a state (county to county or city to city). Programs can vary from the size of a neighborhood to multiple counties.

  • States with a high number of nuisance mosquitoes are more likely to prioritize funding for control programs. For example, in Florida, there is significant support for mosquito control programs in counties that have a high number of biting mosquitoes, not all of which will transmit disease.

  • Most states conduct some level of mosquito surveillance (testing mosquitoes for disease-causing viruses like West Nile, chikungunya, or dengue).