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is the study of the distribution and determinants of disease in a population. Public health epidemiologists monitor the health and illness of a population, investigate the factors that affect the community's health, and recommend interventions to reduce the risk of disease. Epidemiology is practiced in health departments daily and involves principles of surveillance, investigation, laboratory testing, data management and communication.

Zika Virus in Central and South America


Zika-affected areas
Recent travel notices

Current Situation
In May 2015, the World Health Organization reported the first local transmission of Zika virus in the Western Hemisphere with cases identified in Brazil. As of January 15, 2016, local transmission had been identified in at least 14 countries or territories in the Americas, including Puerto Rico.

During the current outbreak, Zika virus infections have been confirmed in several infants with microcephaly (abnormal smallness of the head, associated with incomplete brain development) and in fetal losses in women infected during pregnancy. Exactly how Zika virus infection is associated with pregnancy outcomes is not known; additional studies are planned to learn more about the risks of Zika virus infection during pregnancy. 

Zika virus infection should be considered in patients with new onset of fever, maculopapular rash, arthralgia or conjunctivitis who had recent travel to areas with ongoing Zika transmission in the two weeks before illness started. Clinical disease is usually mild.

What is Zika virus infection?
Zika virus infection is a viral disease spread to people through bites of infected mosquitoes. Mosquitoes become infected by feeding on infected persons. Zika virus is transmitted primarily by Aedes aegypti (Yellow fever mosquito). Aedes albopictus (Asian tiger mosquito) can also spread the virus.

Who gets Zika virus infection?
Anyone traveling to an area where Zika virus is found can become infected. Infections have been reported in travelers returning to the U.S. from affected areas. Those who do not travel to affected areas are not currently at risk of becoming infected because local spread in the continental U.S. has not been reported.

How is Zika virus spread?
Zika virus is mainly spread in a person-to-mosquito-to-person cycle. An infected mosquito bites a person. The person infected by the mosquito will have Zika virus in their blood, especially in the first week of illness. Another mosquito bites that infected person, becomes infected and can then bite another person. People who are infected but who are not sick may still pass the virus on to mosquitoes that bite them. Zika virus can also spread from mother to baby during pregnancy or during the time of birth. 

What are the symptoms of Zika virus infections?
About 80% of people who are infected do not become sick. For the 20% who do become sick, the most common symptoms include fever, rash, joint pain, and conjunctivitis (red eyes). The illness is usually mild and the symptoms typically last several days to a week.

How soon do symptoms occur?
Symptoms usually start 3-7 days after being bitten by an infected mosquito. 

How dangerous is Zika virus infection?
During the 2015–2016 outbreak of Zika virus infection in Brazil, a large increase in the number of babies born with a congenital birth defect called microcephaly was observed. Microcephaly describes a baby or child with a smaller than normal brain and head. Studies are being done to see if the increase in reports of babies with microcephaly is because of an infection with Zika virus. Other causes are also being investigated. In other past Zika virus outbreaks, there have been reports of neurologic syndromes, such as Guillain-Barre Syndrome, in a small number of patients.

What special precautions should pregnant women take to prevent Zika virus?
The role of Zika virus infections during pregnancy is being studied. Out of an abundance of caution, the Centers for Disease Control and Prevention (CDC) advise that pregnant women avoid traveling to countries with ongoing Zika virus infections. If pregnant women need to travel to a country with Zika virus, it is recommended they take the following steps to avoid mosquito bites:

  • Choose an EPA-registered insect repellant and use according to the product label.  Use the repellent day and night because the mosquito species that transmit Zika virus are daytime biters that will also enter buildings and bite at night
  • Use permethrin-treated clothing
  • Cover exposed skin by wearing long sleeves, pants, and hats
  • Sleep indoors in rooms screened windows or air-conditioning, o or use a bed net if you sleep in an room that is exposed to the outdoors

What is the treatment for Zika virus infection?
There is no specific treatment for Zika virus infection. Healthcare providers primarily provide supportive care to relieve symptoms. This may include rest, fluids, and use of over-the-counter medicine.

How can a Zika virus infection be prevented?
There is no vaccine to prevent Zika virus infection. Infections can be prevented by avoiding mosquito bites. This includes wearing long-sleeved shirts, long pants and socks, using insect repellent or permethrin-treated clothing (especially during the daytime when mosquitos are active), using air conditioning or window/door screens to keep mosquitos outside, and eliminating standing water from containers in yards (including bird baths, flower pots, buckets) to stop mosquito breeding.

What should I do if I think I have Zika virus infection?
If you have symptoms of Zika virus infection and have been to an affected area in the past two weeks, contact your healthcare provider.

Where can I get more information?
For additional information, please visit the CDC website You may also call the Health Department. If you have questions about mosquito control programs, you may also contact the Virginia Mosquito Control Association

Contact Information

Communicable Disease Fax Line
(804) 862-6294

Emergency After-Hours Call Number

District Epidemiologist
Louise Lockett, MPH
(804) 862-8986
Tuberculosis Nurse
Angelia Brennan, RN
(804) 862-8901
Communicable Disease Nurse
Catherine Bailey, RN
(804) 862-7617
STI Intervention Specialist
Linda Lewis
(804) 862-8923
CD/TB Outreach
Charmin Davis
(804) 862-8902
STI Intervention Specialist
Sterling Stewart
(804) 862-8927

Resources for Health Care Professionals

Communicable Disease Quarterly Report

Report Communicable Disease

Request for Data

Online Resources

Office of Epidemiology
Home page for VDH’s Office of Epidemiology.  It will connect you with the Divisions of Surveillance and Investigation, Disease Prevention, Environmental Epidemiology, Immunization and Radiological Health.

Disease Regulation Information
Contains the complete regulations for disease reporting and control for Virginia.  You will also find the reportable disease list, conditions reportable by laboratories, outbreak reporting requirements and the reporting form (Epi-1). 

Disease Fact Sheets
Contains all of VDH's disease fact sheets. From head lice to whooping cough to West Nile Virus, this is the first stop for quick, reliable disease information. Fact sheets are also available here in Spanish.

Communicable Disease Chart for Schools
Direct link to the PDF.  Make sure to review the footnotes at the bottom of this document.  Last revised November 1st, 2011.  More information can be found in the VDOE School Health Guidelines (located at the bottom of the page).

Nursing Facility Regulations
Contains a line list of guidelines from VDH’s Office of Licensure and Certification.  The Rules and Regulations for the Licensure of Nursing Facilities in Virginia can be found here.

VDSS Assisted Living Facility Regulations
Contains information on regulations, Code of Virginia, application process, guidelines, forms, training and more.

Successful Strategies for Infection Prevention & ControlThis toolkit contains infection prevention presentations, resources, and tools that have been adapted for the assisted living facility (ALF) and nursing home (NH) setting whenever possible. Much of the tools like infection prevention guidance, fact sheets and surveillance logs, however, are generally applicable to other settings.

EPA Registered Disinfectants
Contains listings of EPA registered antimicrobial products that are effective against HIV, Hepatitis B and C, Norovirus, MRSA and more.

FDA Bad Bug Book
Provides basic facts regarding foodborne pathogens and natural toxins

CDC Health Alert Network
Provides recent and archived health alerts, advisories, updates and informational messages regarding vital health information.

Last Updated: 10-04-2016

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