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Zika Virus Risk-Based Preparedness and Response Guidance for States

State Actions to Consider as Risks Increase for Locally Acquired Cases of Zika
*Does not include guidance specific to U.S. territories

Purpose: This document is intended to guide state public health leaders on actions to consider (first hours - days) upon laboratory confirmation of the first locally acquired (transmitted by the bite of a local vector) case of Zika virus infection in their state. This document may serve as a support tool for states to consider a phased response to Zika virus. It is organized according to actions previously described in the Centers for Disease Control and Prevention’s Public Health Response Plan for Areas at Risk for Local Zika Virus Transmission and High Volume of Travel Associated Cases. 


  • Zika is transmitted to people mainly through the bite of infected Aedes aegypti mosquitoes or through sexual transmission or maternal-fetal transmission.
  • A vaccine or treatment for Zika virus infection is not currently available.
  • Guidance and recommendations will change as more is learned about Zika virus.


  • Zika virus infection in pregnant women is associated with birth defects and adverse pregnancy outcomes, and the evidence for a causal link is growing. Pregnant women represent a highly vulnerable population with special needs. 
  • In areas of active mosquito spread of Zika, there is a risk of transmission through the blood supply.
  • Texas, Florida, and Hawaii are likely to be the US states with the highest risk of experiencing local transmission of Zika virus by mosquitoes, based on prior experience with similar viruses. However, additional states are assumed to be at some risk due to the presence of Aedes aegypti mosquitoes [PDF - 2 pages].
  • Aedes albopictus mosquitoes are more widely distributed in the continental United States and Hawaii and have been proven competent vectors for Zika virus transmission. This vector may also contribute to limited local transmission of Zika virus.

State Risk Assessments:

  1. All states need to provide public information, particularly to pregnant women, and to assess returning travelers who may have contracted Zika virus infection.
  2. States with known Aedes aegypti mosquitoes need to intensively monitor for cases in returning travelers and prepare to find and stop clusters of Zika before they become widespread.
  3. States with Aedes albopictus mosquitos need to presume transmission is possible and be ready to prevent, detect and respond to cases and possible clusters of Zika infection.

Guidelines for a Phased Response to Zika Virus 

The objective of a phased, risk-based response using Zika virus surveillance data is to implement public health interventions appropriate to the level of Zika virus risk in a community, county, or state (see table below). An effective arboviral illness surveillance program and diagnostic testing algorithm that includes testing for Zika virus infection must be in place to recommend a phased response. Effective public health actions depend on interpreting the best available surveillance data and initiating prompt and aggressive intervention when necessary.

Risk category Definition Recommended activities and responses
Preparation Vector present or possible in the state

Response Actions
- The governing officials should appoint a senior representative to coordinate Zika response efforts.
- Pre-identify an incident manager.
- Secure surveillance and control resources necessary to enable emergency response if needed.
- Ensure coordination with state public health officials so vector control and human surveillance activities can be linked.
-Review state and local mosquito control programs and assess capacity and capability.
-Review (or, develop as needed) the state vector-borne disease preparedness and response plan, and tailor as appropriate for Zika.
- Review plans with relevant response partners, identify gaps in preparedness, and develop a plan for improvement.
-Prepare a communication campaign for pregnant women, travelers, healthcare providers, and the public to raise awareness of Zika virus. Include messaging on the risk for sexual transmission, and steps persons can take to prevent it.
- Update scripts for state call centers to include Zika messaging.
-Enhance surveillance for travel-associated Zika cases and possible sexual transmission from travel cases.
- Reach out to clinicians in the state and provide guidance for management and testing of possible cases.
- Review state and commercial laboratory capacity to rapidly test specimens for Zika virus.
-Plan preparedness and mitigation activities to reduce the likelihood of transmission from mosquitoes, including: reduction of habitat/potential breeding sites, initiate community clean-up efforts, initiate public information campaigns encouraging yard clean up, use of insecticides, encouraging placement of window screens etc.
- Review (and as necessary, conduct) mosquito surveillance activities to assess whether historic maps of Aedes aegypti and Aedes albopictus distribution are accurate.
Pregnant Women Outreach
- Plan enhanced surveillance for suspected Zika virus infections, including for pregnant women through OB/GYN clinics, etc).
-Identify resources that could be used for interventions for pregnant women (products to develop Zika Prevention Kits for pregnant women, resources for communications campaigns, etc).
- Prepare a registry to collect information on Zika cases during pregnancy that could be used for future monitoring and follow-up of birth outcomes. This will be used to report cases to the National Zika Birth Registry.
Blood Safety
- Reach out to local blood collection centers, and consult with them on blood safety contingency plans.


Mosquito Season
(Aedes aegypti or Aedes albopictus mosquito seasonal biting activity)

Continued Preparation, plus
Response Actions
Organize regular meetings between the pre-identified Incident Manager and state vector preparedness and response partners to discuss plans and progress.
- Initiate a communications campaign, with primary messaging focusing on awareness, personal protection against mosquitoes, and residential source reduction.
- Deploy messages encouraging travelers returning from areas with Zika transmission to take precautions upon return (actively take steps to prevent mosquito bites for at least 3 weeks) to reduce the risk of spread to local mosquito populations.
-Rapidly follow up on suspected cases through laboratory testing. Take a complete patient history; establish lack of travel, no transfusion or tissue transplantation, no sexual exposure to a traveler. Assess patient’s geographic area of risk for exposure (i.e., Where were they likely exposed? Home? Other place?)
-When travel-associated cases or cases among their sexual contacts are identified, counsel them to take precautions to avoid exposure to local mosquito populations (stay indoors in screened, air-conditioned rooms, use of personal repellents, consider mosquito reduction activities around home).
-Encourage healthcare providers to immediately reports results for any positive or equivocal cases.

-Explore focused community interventions to disrupt breeding grounds, such as tire collections and waste removal in at-risk areas. Leverage partnerships with local governments and non-profits for support.

Confirmed Local Transmission by Mosquitoes
(single case, or cases clustered in a single household/community in a county or jurisdiction)

Response as in category 1 plus: 
Response Actions:
- Activate the state incident management structure. 
- Determine if there is a need for assistance from a CDC field team (e.g., Epi Aid or rapid response team) to provide on the ground technical, risk communication, vector control and/ or logistical support.
- As appropriate, issue press release/media statement and intensify visible activities in the county to increase attention to Zika virus transmission risk and personal protection measures (flyers, community leaders, social media).
-Monitor local news stories and social media postings to determine if information is accurate, identify messaging gaps, and make adjustments to communications as needed. 
- Intensify surveillance for human cases in a 150-yard radius (or other boundary, as deemed appropriate) around home or other likely sites of exposure). Consider conducting household and door-to-door surveillance for clinically compatible cases.
- Recommend cases stay in air-conditioned/screened accommodations and use personal precautions to reduce mosquito bites.
- Enhance local surveillance for human cases (consider local clinician outreach, syndromic surveillance in nearby hospitals, etc).
- If not previously done, conduct a rapid insecticide resistance study for local mosquito populations.
- Conduct intensified larval and adult mosquito control in a 150-yard radius (or other boundary, as deemed appropriate) around case-patient home, including residential habitat reduction (trash cleanup, etc.) and outdoor space spraying. Although likely not needed in most areas, in areas where A/C and screens aren’t widely available, consider offering homeowners Indoor Residual Spraying (IRS).
Pregnant Women:
- Deploy targeted communications, surveillance, and monitoring programs for pregnant women in the county/jurisdiction.
- Deploy the registry of Zika cases during pregnancy for monitoring and follow-up of birth outcomes.
Blood Safety
- Notify local blood collection agencies for awareness.
- Review CDC toolkit for investigation of transfusion-transmitted infection.

3 Widespread Local Transmission by Mosquitoes
(multiple locations within a county/jurisdiction)

Response as in category 2 plus: 
Response Actions
- Determine the geographic boundaries that will be used for aggressive response efforts (county/jurisdiction, health department coverage area, zip code, etc).
- County/jurisdiction designated as an area of “active Zika transmission”. 
-State should notify CDC (770-488-7100).
-Incident Manager should provide regular situation updates to keep public and partners informed of evolving situation.
- Intensify county-wide (or jurisdiction-wide) outreach (newspaper, radio, social media, call centers).
- Intensify county-wide (or jurisdiction-wide) surveillance for human cases (consider clinician outreach, syndromic surveillance in hospitals, etc.).
- Intensify and expand vector control efforts. Control plans should be tailored to local needs, but might include ground application, aerial spraying, or a combination of the two, and should include both adult and larval mosquito control methods, repeating applications as necessary to achieve adequate control.
-For areas where A/C and screens aren’t widely available, consider adding Indoor Residual Spraying (IRS) to vulnerable homes.
- Monitor effectiveness of vector control efforts through mosquito trapping surveillance.
Pregnant Women
-Advise pregnant women to consider postponing travel to the county/jurisdiction.
- Advise men in the county/jurisdiction to use condoms or abstain from sexual contact with pregnant women.
- Implement intervention plans for high risk populations (pregnant women). Options to consider include mosquito-proofing homes through installation of screens and provision of air-conditioning if necessary, as well as household vector control, and distribution of Zika Prevention Kits (ZPK’s).  
- Initiate testing of asymptomatic pregnant women.
- Consider retrospective enhanced surveillance in health facilities to establish the earliest known date of local human infection for future counseling/ testing of asymptomatic pregnant women.
Blood Safety
- Blood centers with collections in county/jurisdiction should follow FDA guidance for an area of active transmission, including outsourcing blood if laboratory screening or pathogen reduction is unavailable.
-Blood centers in other areas and states should follow FDA guidance for deferring blood donations for people who have a recent travel history to this county/jurisdiction.

4 Local Transmission by Mosquitoes in Multiple Counties

Response as in category 3, plus:
- Expand response activities regionally or state-wide.