What We Know about Zika

After Birth

Babies and children can be infected with Zika.

  • The primary way that babies and children get Zika is through bites of two types of mosquitoes. Information on safely preventing mosquito bites can be found below or at CDC’s Avoid Mosquito Bites page.
  • Zika virus has been found in breast milk, and there have been several reports of Zika virus infection in babies from breastfeeding.1,2,3 However, there have been no reports of health problems in babies resulting from breast milk from a mother with Zika virus infection. Because current evidence suggests that the benefits of breastfeeding outweigh the risk of Zika virus spreading through breast milk, CDC continues to encourage mothers to breastfeed, even in areas with risk of Zika. CDC continues to study Zika virus and breast milk and will update recommendations as new information becomes available.
  • Common symptoms of Zika are fever, rash, joint pain, and red eyes. Symptoms usually go away within a few days to one week. Many people infected with Zika don’t have symptoms.
  • There is no vaccine or medicine for Zika. For more information about treatment and prevention.

During Pregnancy

Birth defects, including microcephaly, and other problems have been reported in babies born to women infected with Zika during pregnancy.

  • Zika virus can be passed from a woman to her fetus during pregnancy or around the time of birth. We are studying how Zika virus affects pregnancies.
  • Since May 2015, Brazil has had a large increase in cases of Zika. During this outbreak, Brazilian officials reported an increase in the number of babies born with microcephaly, a condition in which a baby’s head is smaller than expected when compared to babies of the same sex and age, in areas affected by Zika. Recently, CDC concluded that Zika virus infection during pregnancy is a cause of microcephaly and other severe fetal brain defects.
  • Pregnancy loss and other pregnancy problems have been reported in women infected with Zika during pregnancy. Zika has been linked with other birth defects, including eye defects, hearing loss, and impaired growth.
  • Some babies infected with Zika before birth may not be born with microcephaly but later experience slowed head growth and develop microcephaly after birth.
  • Not all babies whose mothers had Zika during pregnancy are born with health problems. Researchers are working to better understand how common it is that having Zika during pregnancy causes problems.
  • Infection with Zika virus at later times, including around the time of birth or in early childhood, has not been linked to microcephaly.
  • A pregnant woman can pass Zika virus to her fetus during pregnancy. Zika is a cause of microcephaly and other severe fetal brain defects. We are studying the full range of other potential health problems that Zika virus infection during pregnancy may cause.
  • A pregnant woman already infected with Zika virus can pass the virus to her fetus during the pregnancy or around the time of birth.
What Parents Can Do

Prevent mosquito bites.

  • Dress your child in clothing that covers arms and legs.
  • Cover crib, stroller, and baby carrier with mosquito netting.
  • Use insect repellent as directed.
  • Do not use insect repellent on babies under 2 months old.
  • Do not use products containing oil of lemon eucalyptus or para-menthane-diol on children younger than 3 years old.
  • In children older than 2 months, do not apply insect repellent onto a child’s hands, eyes, mouth, or to irritated or broken skin.
  • Never spray insect repellent directly on a child’s face. Instead, spray it on your hands and then apply sparingly, taking care to avoid the eyes and mouth.

Control mosquitoes inside and outside your home.

If your child has symptoms, take him or her to see a doctor or other healthcare provider.

  • For children with Zika symptoms of fever, rash, joint pain, or red eyes who have traveled to or lived in an area with risk of Zika, contact your child’s healthcare provider and describe where you have traveled.
  • Fever (≥100.4° F) in a baby less than 2 months old always requires evaluation by a medical professional. If your baby is less than 2 months old and has a fever, call your healthcare provider or get medical care.
Just for Kids

Microcephaly happens for many reasons, and many times the cause is unknown.

  • Genetic conditions, certain infections, and toxins can cause microcephaly. If your child has microcephaly, his or her doctor or other healthcare provider will look for the underlying reason. However, for about half of children with microcephaly, the underlying cause is never discovered.
  • If you have a child with microcephaly, it is unlikely that it had to do with Zika if you did not travel to an area with risk of Zika during pregnancy.
  • Although head size reflects brain size, head size does not always predict short- or long-term health effects. While some children with microcephaly can have seizures, vision or hearing problems, and developmental disabilities, others do not have health problems.

What We Don’t Know about Zika

  • We do not know how often Zika is passed from a woman to her fetus during pregnancy or around the time of birth.
  • We do not know whether the timing of the woman’s Zika virus infection during pregnancy, or the severity of a woman’s symptoms, affect her pregnancy.
  • We do not know the long-term health outcomes for infants and children with Zika virus infection.

What CDC Is Doing to Learn More

  • Developing laboratory tests to diagnose Zika as quickly as possible.
  • Conducting research on the link between Zika and microcephaly and other developmental delays.
  • Identifying new areas with risk of Zika and updating the US Zika Pregnancy Registry daily to improve our understanding of the how Zika affects mothers and their children.
  • Testing different mosquito species to find out whether they carry Zika.
  • Providing advice to US travelers returning from areas with risk of Zika; and, supporting US states and territories already affected by Zika.
  • Preparing states and Americans with prevention actions in advance of mosquito season.


  1. Blohm GM, Lednicky JA, Márquez M, et. al. Evidence for Mother-to-Child Transmission of Zika Virus Through Breast MilkExternal. Clinical Infectious Diseases. In Press.
  2. Gregory CJ, Oduyebo T, Brault AC, et. al. Modes of Transmission of Zika VirusExternal. The Journal of Infectious Diseases.
  3. Colt S, Garcia-Casal MN, Peña-Rosas JP, et. al. Transmission of Zika virus through breast milk and other breastfeeding-related bodily fluids: A systematic reviewExternal. PLOS Neglected Tropical Diseases.