Zika Virus: What We Need To Know

Epidemiology of Zika Virus Disease

Share this article

Zika virus disease (Zika) outbreaks are prompting worldwide attention because of a potential link to birth defects such as microcephaly, a birth disorder of the brain that results in babies being born with abnormally small heads. Microcephaly causes severe developmental issues and sometimes death.

What is Zika virus?

Zika is a disease caused by Zika virus, which is transmitted to people primarily through the bite of an infected Aedes species mosquito. The Zika virus is closely related to dengue, yellow fever, Japanese encephalitis, and West Nile virus.

What are the symptoms and diagnosis of Zika virus infection?

  • About one in five people infected with Zika virus becomes ill.
  • The most commonly reported symptoms of Zika virus are fever, rash, joint pain, or conjunctivitis (red eyes). Other common symptoms include muscle pain and headache. The incubation period (the time from exposure to symptoms) for Zika virus disease is not known, but is likely to be a few days to a week.
  • People usually don’t get sick enough to go to the hospital, and they very rarely die of Zika virus.
  • Zika virus usually remains in the blood of an infected person for about a week, but it can be found longer in some people.
  • Zika virus diagnosis can only be confirmed by laboratory testing for the presence of Zika virus RNA in the blood or other body fluids, such as urine or saliva.
  • Figure 1 (below) summarizes the clinical symptoms of Zika virus disease.

Figure 1. 


Source: CDC, 2016

How is Zika virus spread?

Although Zika virus is primarily transmitted through the bite of infected mosquitoes, there are several other modes of transmission. The modes include:

  • Mother-to-child transmission during pregnancy or during birth
  • Blood transfusion
  • Sexual transmission
  • Laboratory exposure
  • Organ or tissue transplantation.

Where is the Zika virus now?

According to the Centers for Disease Control and Prevention (CDC) and the World Health Organization, the current outbreaks of Zika virus are occurring in many countries as shown in Figure 2 below. In May 2015, the Pan American Health Organization issued an alert regarding the first confirmed Zika virus infections in Brazil.

Figure 2. 


Source: CDC, 2016

The CDC reported that although local transmission of the virus has not been documented in the continental United States, Zika virus infections have been reported among travelers visiting or returning to the United States. As of February 10, 2016, 52 travel-associated Zika virus disease cases were reported in the United States, and 1 travel-associated and 9 locally acquired cases were identified in the U.S. territories. See Figure 3 below.

Figure 3. 


Source: CDC, 2016

What treatments exist for Zika virus infection?

There is no vaccine to prevent or specific medicine to treat Zika virus infections. The infected person should seek medical care and advice.

Zika Virus in Pregnancy 

Does Zika virus infection in pregnant women cause birth defects?

The current data suggest that pregnant women can be infected with Zika virus in any trimester. There have been multiple reports of a neurologic birth defect (microcephaly) and other poor pregnancy outcomes in babies of mothers who were infected with Zika virus while pregnant.

In 2015, Brazil national health authorities reported potential neurological and autoimmune complications of Zika virus disease. In addition, the local health authorities have observed an increase in babies born with microcephaly in northeast Brazil.

What are the recommendations for pregnant women?

Health care providers should make the following recommendations regarding the Zika virus:

  • Pregnant women (in any trimester):
    • Counsel pregnant women to consider postponing travel to any area where Zika virus transmission is ongoing.
    • If pregnant women must travel to one of these areas, advise them to strictly follow steps to prevent mosquito bites during the trip.
    • If a woman has a male partner who lives in or has traveled to an area where Zika virus is spreading, advise her to either abstain from sex or use condoms consistently and correctly for the duration of the pregnancy.
  • Women who are trying to become pregnant:
    • Advise women to talk to a health care provider about their plans to become pregnant and the risk for Zika virus infection.
    • Advise women and their male partners to strictly follow steps to prevent mosquito bites during a trip to an area with ongoing Zika virus transmission.

What is the clinical guidance for testing for Zika virus during pregnancy?

Figure 4 (below) shows the testing guideline for a pregnant woman with a history of travel to an area with ongoing Zika virus transmission.

Figure 4. 


Source: CDC, 2016

Figure 5 (below) shows the testing guideline for a pregnant woman residing in an area with ongoing Zika virus transmission, with or without clinical illness consistent with Zika virus disease.

Figure 5.


Source: CDC, 2016

If a mother had Zika virus infection during pregnancy, should she breastfeed her infant?

Based on available evidence, the benefits of breastfeeding infants outweigh any theoretical risk related to Zika virus infection.

How treat pregnant women with diagnoses of Zika virus disease?

No specific antiviral treatment is available for Zika virus disease. In a pregnant woman with laboratory evidence of Zika virus in serum or amniotic fluid, serial ultrasounds should be considered to monitor fetal anatomy and growth every 3–4 weeks. Referral to a maternal/fetal medicine or infectious disease specialist with expertise in pregnancy management is recommended.

How can pregnant women protect themselves against Zika virus?

The best way to prevent Zika virus is to prevent mosquito bites.

  • Wear long-sleeved shirts and long pants.
  • Stay in places with air conditioning or that use window and door screens to keep mosquitoes outside.
  • Use U.S. Environmental Protection Agency (EPA)-registered insect repellents (bug spray). Always follow the instructions on the label and reapply every few hours.
  • Eliminate mosquito breeding sites, such as containers with standing water.
  • In Figure 6 below, CDC summarizes the information for pregnant women regarding Zika virus.

Figure 6.


Source: CDC, 2016

Can pregnant and breastfeeding women use insect repellent? 

Yes. Use EPA-registered insect repellents. When used as directed, these insect repellents are proven safe and effective even for pregnant and breastfeeding women.

Preventing Zika Virus

What can people do to prevent becoming infected with Zika virus?

There is no vaccine to prevent or medicine to treat Zika virus. The best way to prevent disease spread by mosquitoes is to adhere to the CDC recommendations below:

  • Wear long-sleeved shirts and long pants.
  • Stay in places with air conditioning or that use window and door screens to keep mosquitoes outside.
  • Sleep under a mosquito bed net if temperature-controlled or screened rooms are not available or if sleeping outdoors.
  • Use EPA-registered insect repellents. When used as directed, insect repellents are proven safe and effective even for pregnant and breastfeeding women.

Check out the following link to find out more about Zika virus: https://www.washingtonpost.com/news/to-your-health/wp/2016/01/21/zika-virus-faq-more-than-a-million-infected-globally-a-dozen-in-the-united-states/


Hennessey M, Fischer M, Staples JE. Zika virus spreads to new areas—region of the Americas, May 2015–January 2016. MMWR Morb Mortal Wkly Rep 2016;65:55–58. doi: http://dx.doi.org/10.15585/mmwr.mm6503e1. Retrieved from: http://www.cdc.gov/mmwr/volumes/65/wr/mm6503e1.htm?s_cid=mm6503e1.htm_w

Jamieson D. 10 Questions about Zika: The CDC answers. (2016.) Retrieved from: http://www.medscape.com/viewarticle/859014_2

Oduyebo T, Petersen EE, Rasmussen SA, et al. Update: Interim guidelines for health care providers caring for pregnant women and women of reproductive age with possible Zika virus exposure—United States, 2016. MMWR Morb Mortal Wkly Rep 2016; 65:122–127. doi: http://dx.doi.org/10.15585/mmwr.mm6505e2. Retrieved from: http://www.cdc.gov/mmwr/volumes/65/wr/mm6505e2.htm?s_cid=mm6505e2.htm_w

Petersen EE, Staples JE, Meaney-Delman, D, et al. Interim guidelines for pregnant women during a Zika virus outbreak—United States, 2016. MMWR Morb Mortal Wkly Rep 2016;65:30–33. doi: http://dx.doi.org/10.15585/mmwr.mm6502e1. Retrieved from: http://www.cdc.gov/mmwr/volumes/65/wr/mm6502e1.htm?s_cid=mm6502e1_w

Schuler-Faccini L, Ribeiro EM, Feitosa IM, et al. Possible association between Zika virus infection and microcephaly—Brazil, 2015. MMWR Morb Mortal Wkly Rep 2016;65:59–62. doi: http://dx.doi.org/10.15585/mmwr.mm6503e2. Retrieved from: http://www.cdc.gov/mmwr/volumes/65/wr/mm6503e2.htm?s_cid=mm6503e2.htm_w

Staples JE, Dziuban EJ, Fischer M, et al. Interim guidelines for the evaluation and testing of infants with possible congenital Zika virus infection—United States, 2016. MMWR Morb Mortal Wkly Rep 2016;65:63–67. doi: http://dx.doi.org/10.15585/mmwr.mm6503e3. Retrieved from: http://www.cdc.gov/mmwr/volumes/65/wr/mm6503e3.htm?s_cid=mm6503e3.htm_w

U.S. Centers for Disease Control and Prevention. Zika virus. (February 21, 2016.) Retrieved from: http://www.cdc.gov/zika/

World Health Organization. Zika virus, fact sheet. (February 2016.) Retrieved from: http://www.who.int/mediacentre/factsheets/zika/en/

Subscribe to our mailing list

* indicates required
What are you interested in?

Leave a Comment