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What you need to know about the Zika virus: New information on sexual transmission

February 04, 2016
Zika Mosquito

News of the Zika virus has exploded internationally, specifically in the past several weeks with the Centers for Disease Control and Prevention (CDC) issuing a warning to pregnant women visiting areas where the virus has spread, and how to protect themselves when having sex with someone who has returned from the many outbreak sites.

The CDC has now issued a travel alert that includes over 25 regions outside the U.S., where the Aedes aegypti mosquito (and possibly the Aedes albopictus) carries and transmits the virus. While both of these mosquitoes can be found in the South and other parts of the United States, no locally transmitted Zika cases had been reported until Feb. 2, when the CDC announced that the Zika virus had been sexually transmitted in Texas – the first known case of the virus being locally acquired in the continental United States in the current outbreak – by a women having sex with a man who had recently returned from Venezuela. For now, the CDC is recommending that men having sex after traveling to the outbreak areas use condoms, and that pregnant women should avoid contact with semen from men recently exposed to the virus. CDC officials say they will issue further guidelines soon.

There have also been isolated cases of the Zika virus being transmitted during blood transfusions, but none confirmed in this country. Cases reported in the U.S. involving returning travelers are expected to increase. And, according to the CDC, these imported cases could eventually result in local spread of the virus in some areas of the U.S.

Massachusetts state health officials confirmed one case of the Zika virus in the state on Jan. 28, and said additional cases are possible. The Massachusetts Department of Public Health (DPH) is working closely with the CDC to coordinate testing for symptomatic pregnant women who have recently traveled to countries with identified Zika transmission. Currently all evaluations are being handled by the CDC. 

Dr. Andrew Healy in Maternal Fetal Medicine at Baystate Medical Center offers answers to important questions about Zika virus you need to know.

Q. What is the Zika virus and how is it transmitted?

A. The Zika virus is a mosquito-borne illness – in the same family as yellow fever, dengue, and West Nile viruses – and it is spread through the bite of an Aedes mosquito. While it is generally believed that it cannot be transmitted from person to person, observational evidence in some small studies suggest those infected with Zika can pass the virus to others through sexual intercourse. That belief has now been documented in Texas, where the CDC has confirmed a case of Zika transmitted through sexual intercourse. While most people will have no symptoms, some may experience fever, joint and muscle pain, rash, headache, and conjunctivitis. There is no vaccine or medication to treat the virus, but reports say that researchers are working on both.

Q. Who is at risk and should people be concerned about traveling to Zika-affected areas?

A. Everyone is at risk for contracting the Zika virus by mosquito bite when traveling in the alert areas. However, people in general should not be concerned about traveling to Zika-affected areas, with the great exception of pregnant women or women who are trying to become pregnant. The virus has been associated with an alarming rise in the number of babies in Brazil being born with a birth defect known as microcephaly – where babies are born with small, underdeveloped skulls – and other poor pregnancy outcomes, as well as Guillain-Barre syndrome, which is characterized by paralysis caused by the immune system attacking the nervous system. If you are pregnant and have plans to travel to regions where the Zika virus has spread, contact your doctor beforehand. While a direct causal link between Zika virus and birth defects has not been established, and more research is needed, the large increase in cases of microcephaly was enough of a reason for the CDC to issue a travel alert.

Q. What should a woman do if she was pregnant while visiting one of the infected areas, or became pregnant shortly after?

A. The federal Centers for Disease Control and Prevention (CDC) has issued interim evaluation and treatment guidelines for infants born to mothers who traveled or lived in areas with Zika virus outbreaks during their pregnancy, as well as interim guidelines for U.S. healthcare providers caring for pregnant women who have traveled to the areas where Zika virus transmission is active. Pregnant women with a history of concerning symptoms such as fever, joint and muscle pain, rash, headache, and conjunctivitis during their trip or within two weeks of travel are candidates for testing. Patients with a history of travel to at-risk areas, but no history of symptoms, should be offered a serial fetal ultrasound to detect microcephaly and/or intracranial calcifications. Amniocentesis may be also be considered depending on the results. Pregnant women should contact their obstetric provider if they have a history of recent travel to at-risk areas.

Q. How can you prevent being infected with the Zika virus?

A. The best way to prevent being infected with the Zika virus is to avoid being bitten by a mosquito in the affected areas. Insect repellents, especially those containing DEET, should be used. Also, wear protective clothing like long-sleeved shirts and pants, and avoid freestanding water. The Aedes mosquito breeds and rests in small pools of water and moist environments around people’s homes such as in flower pots or animal drinking pans. Keep windows closed and use air-conditioning, if needed, in these areas. Clothing should also be treated with permethrin prior to travel.

Q. What countries are included in the current CDC advisory?

A. As of Feb. 2, countries and territories with Zika virus transmission included in the current CDC advisory are in the Caribbean – Barbados, Curacao, Dominican Republic, Guadeloupe, Haiti, Martinique, Puerto Rico, Saint Martin, and US Virgin Islands; in Central America – Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua, and Panama; Pacific Islands – American Samoa and Samoa; South America – Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Paraguay, Suriname, and Venezuela; as well as Cape Verde and Mexico.

For the latest CDC travel advisories visit: