Zika: What You Need to Know—UPDATED

Jul 1, 2016

By Rohit Bhalla, DO, FACP
Chief, Section of Infectious Diseases
University Medical Center of Princeton

Zika, a mosquito-borne viral infection that has been linked to a serious birth defect of the brain, has been declared a public health emergency by the World Health Organization.

While most people infected with Zika virus will not develop any symptoms, the infection poses a significant concern to pregnant women, especially as it continues to spread.

The Centers for Disease Control and Prevention (CDC) recommended that pregnant women postpone travel to areas where Zika virus transmission is ongoing or, if they must travel to those regions, to take strict precautions.

Further, the CDC warned that the number of cases among travelers visiting—or returning to—the United States will likely increase. This could result in the local spread of the virus in states with warmer climates where mosquitos are prevalent.

What is Zika?

Zika is a virus spread primarily through the bite of an infected Aedes aegypti mosquito. These are the same mosquitos that spread dengue and chikungunya viruses. The CDC describes the mosquitos as aggressive daytime biters, though they also bite at night.

Where is Zika?

Outbreaks are occurring in many countries and territories. In the U.S., we have seen travel-associated cases but no local transmission of Zika virus disease within the 50 states. However, local mosquito-borne transmission has been reported in the commonwealth of Puerto Rico, the US Virgin Islands, and American Samoa.

Click on the graphic below to view the CDC's map of areas with active Zika transmission.


What are the symptoms of Zika?

About 1 in 5 people infected with Zika will get sick, according to the CDC. The most common symptoms are:

  • Fever
  • Rash
  • Joint pain
  • Conjunctivitis (red eyes)

Symptoms typically start two to seven days after being bitten by an infected mosquito. Often the symptoms are so mild that people might not even know they are infected.

If you develop symptoms of Zika, see your doctor and make sure to tell him or her if you have recently traveled.

How is Zika transmitted?

In simplest terms, a mosquito bites a person who is already sick. The mosquito gets infected. Infected mosquitos can then bite healthy people and spread the infection. More sick people equals more infected mosquitos equals more sick people.

Additionally, the virus can be transmitted from a pregnant mother to her baby during pregnancy or around the time of birth.

The CDC has also noted isolated cases of Zika being spread through blood transfusions and sexual contact.

What is the concern for pregnant women?

There is growing evidence of a link between Zika and microcephaly, a congenital condition associated with incomplete brain development. Babies with microcephaly are born with smaller-than-expected heads and are susceptible to a variety of physical and developmental issues that range from mild to severe.

Microcephaly is rare, but in Brazil alone, 3,500 cases occurred between October 2015 and January 2016. This is far above the expected number.

In addition to microcephaly, other poor outcomes have been associated with Zika infection during pregnancy. As a result, the CDC issued these recommendations for pregnant women:

  • Postpone travel to affected areas, if possible. Specific areas where Zika virus transmission is ongoing are likely to change over time. Visit for the most up-to-date travel information.
  • If you must travel to one of the Zika-affected areas, strictly follow precautions to avoid mosquito bites.
  • Seek testing for Zika virus if you return from a Zika-affected area and develop two or more symptoms within two weeks or if an ultrasound shows evidence of microcephaly or intracranial calcification in your baby.
  • Discuss your male sex partner's potential exposure and history of Zika-like illnesses with your doctor. Men who reside in or have traveled to an area of active Zika virus transmission should consistently and correctly use condoms during sex or abstain from sexual activity for the duration of the pregnancy.

Women who are trying to become pregnant should talk to their doctor before traveling to an area affected by Zika.

Can Zika cause Guillain-Barre syndrome (GBS)?

It is still unknown if Zika causes GBS, but Brazilian health officials have reported an increased number of people affected with the rare condition in which a person's immune system damages the nerve cells, causing muscle weakness and sometimes paralysis.

Most people recover from GBS, but some have permanent damage. In rare instances, GBS has resulted in death.

What can you do to prevent Zika infection?

There is no vaccine for the Zika virus. The best defense is to protect yourself against mosquito bites when traveling to areas affected by a Zika outbreak. The CDC recommends:

  • Wear long-sleeved shirts and long pants.
  • Stay in places with air conditioning or that use window and door screens to keep mosquitos outside.
  • Use insect repellants that are registered with the federal Environmental Protection Agency (EPA). All EPA-registered insect repellants are evaluated for safety and effectiveness. Follow all instructions and reapply as directed.
  • Treat clothing and gear with permethrin or buy permethrin-treated items, such as boots, pants, socks and tents.
  • Sleep under a mosquito bed net if you are sleeping outdoors.

If you are concerned you might have been exposed to the Zika virus and have any concerns about your health or the health of your baby, contact an infectious disease specialist.

To find a doctor with Princeton HealthCare System, call (888) 742-7496 or visit