Zika Cases in the United States

Background

• Prior to 2014, very few travel-associated cases of Zika were identified in the United States.
• In 2015 and 2016, large outbreaks of Zika virus occurred in the Americas, resulting in an increase in travel-associated cases in U.S. states, widespread transmission in Puerto Rico and the U.S. Virgin Islands, and limited local transmission in Florida and Texas.
• In 2017, the number of reported Zika cases in the United States started to decline.
• Since 2018, there have been no reports of Zika virus transmission by mosquitoes in the continental United States.
• Since 2019, there have been no confirmed Zika cases reported from U.S. territories.
• CDC is notified of cases by state and local health departments using standard case definitions.

Zika cases by year

The following table shows Zika cases* reported in the United States from 2015 through 2022 to ArboNET, a national surveillance system that tracks viruses spread by mosquitoes and ticks.

*Includes confirmed and probable disease cases

**Locally acquired cases reported from Florida and Texas in 2016 and 2017

†Includes cases acquired through other routes (e.g., sexual and laboratory transmission)

††Since 2019, all locally acquired cases of Zika in the U.S. territories were diagnosed by antibody testing. Since antibodies against Zika virus can persist for years after infection, serology cannot distinguish between a recent or past infection. Additionally, Zika and dengue virus antibodies cross-react, making it difficult to diagnose which virus is the cause of the current illness. Since 2019, there have been no confirmed Zika virus disease cases reported from U.S. territories.