How to Prevent the Zika Virus

While many people infected with Zika virus will not show symptoms or will only have mild illness, the transmission from mother to child during pregnancy can be serious and lead to a rare birth defect known as microcephaly. Currently, there is neither a vaccine nor any specific treatment for this virus, so preventing Zika infection in the first place is the only true means of protection.

The main mode of transmission is a bite from a Zika-carrying mosquito, so wearing insect repellant, covering up, and taking other steps to stay bite-free when you are living in or traveling to an endemic area is crucial.

Another key Zika prevention step: Using condoms (or abstaining from sex) if a partner has been in a high-risk area of the world. Zika can pass from one person to another through semen, vaginal fluids, and saliva, so it's possible for someone to get the virus without ever having been bitten by an infected mosquito themself.

Preventing Mosquito Bites

The Zika virus is primarily spread by the Aedes aegypti mosquito, a strain prevalent in tropical and subtropical regions across the globe. This mosquito is recognized by white markings on its legs and another on its back in the shape of a lyre (a U-shaped harp).

Mosquitoes that spread Zika bite during the day and night.

The Aedes aegypti mosquito can be found in most equatorial countries but is associated with large-scale infestations in South America, Central America, and the Caribbean, Central and East Africa, India, Southeast Asia, and northern Australia.

In the United States, the mosquito is most commonly seen on the Gulf Coast running from Texas to Florida, although there are no current reported transmissions of the virus in the entire U.S.

If you are in an area where there is a risk of mosquito-borne transmission, there are several things you can do to prevent bites:

• Use an insect repellent. Mosquito repellent options include those made with DEET (minimum 10% concentration), picaridin (also known as icaridin or KBR 3023), and lemon eucalyptus oil.
• Wear protective clothing. This includes wearing long sleeves, long pants, socks, and shoes. Pant legs can be tucked into boots or socks for added protection.
• Sleep under a mosquito net. Repellent-infused netting is available through specialty retailers.
• Get rid of standing water. Mosquitoes can breed in even small amounts of water around the house. This includes flower vases and blocked gutters.
• Place mosquito dunks in your yard. These larvicide-containing cakes kill mosquito larvae before they can grow into adults. They are safe for people and pets, and available in many yard supply stores and online. When there is an outbreak, your local health department may even provide them for free.
• Keep mosquitoes from getting inside. Close windows and vents, and only keep doors and windows open if they are fitted with screens.

Preventing Exposure to Zika Through Sex

Zika can be passed from one person to another through vaginal, anal, or oral sex.

According to the CDC, there is evidence of female/male and male/male sexual transmission; while female/female transmission hasn't been reported, it is possible from a biological perspective.

If you or your partner reside in or have just returned from an area where Zika is endemic, there are several things you both can do. This is important regardless of whether or not you or your partner are showing symptoms (most commonly, infected people won't have any symptoms, so it is possible to have the virus but feel fine):

• Use condoms. The CDC currently recommends using condoms for at least eight weeks following the return of your partner if asymptomatic and at least six months if symptomatic. Short of abstinence, this is the best all-around form of protection from Zika.
• Use insect repellent. This should be used by both you and your partner for at least three weeks following their return. Doing so may prevent human-mosquito-human transmission.
• Use dental dams during oral sex. Dental dams should be used for oral-penile sex, oral-vaginal sex, or oral-anal sex. If you don't have a dental dam, you can make one.
• Avoid sharing sex toys. You should also use condoms on sex toys and disinfect the toy between uses.

If you or your partner develop Zika symptoms, testing should be sought from the municipal or state health department.

If Planning to Conceive

If you are trying to conceive and you or your partner have been in an area where Zika is a concern, you may want to stop until a doctor tells you otherwise. The amount of time the virus remains in bodily fluids varies, but it can stay the longest in semen.

During this time, if the virus is passed to a pregnant woman, it's possible that her baby may develop an abnormally small head and brain (microcephaly).

According to research published by the CDC in 2018, of 1,450 children whose mothers had been infected with Zika during pregnancy, no less than 6% of them had microcephaly.

Neither preconception testing for Zika nor the testing of an asymptomatic partner is currently advised by the CDC.

Preventing Blood Exposure

While there have been several cases in Brazil where the Zika virus has been passed through a blood transfusion, the risk is considered low. While research is ongoing, the current evidence suggests that the virus is less able to persist in blood and will likely clear within 13 days.

In an effort to further reduce the risk of transmission, guidelines implemented by the U.S. Food and Drug Administration (FDA) recommend routinely screening blood donations and removing any that test positive for the Zika virus.

If this doesn't offer you enough assurance, you can make an autologous donation in which you donate blood for yourself before surgery or a planned medical procedure. Autologous donations require a doctor's prescription. Contact your provider to find out if you are eligible to make such a donation.

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Vaccine Development

Although no Zika vaccine is currently available, there are several undergoing various phases of clinical research.

The three types of vaccines currently under investigation are broadly categorized as live-attenuated vaccines (using weakened live viruses that cannot cause disease), inactivated vaccines (using killed viruses), and vectored vaccines (which use a modified harmless virus to carry an antigen, DNA, or RNA to target cells).

Among the Zika vaccine candidates showing the greatest promise as of 2020, which are in various phases:

• VRC5283, developed in coordination with the National Institute of Allergy and Infectious Diseases (NIAID), which uses a modified Japanese encephalitis virus to deliver DNA to target cells to induce a Zika-specific antibody response
• GLS-5700, being developed by Invovio Pharmaceuticals, which is taking a similar approach to VRC5283
• mRNA-1325, being developed by Moderna Therapeutics, which is built on a messenger RNA platform similar to the one used to develop Moderna's COVID-19 vaccine
• rZIKV/D4Δ30-713, a live attenuated vaccine also developed under the auspices of NIAID
• ChAdOx1 Zika, a live attenuated vaccine being developed by the University of Oxford
• ZPIV, an inactivated, whole-killed Zika vaccine being developed under the auspices of NIAID
• TAK-426, being developed by Takeda Pharmaceuticals, another inactivated, whole-killed Zika vaccine
• VLA160, an inactivated, whole-killed vaccine developed by Valneva GmbH that includes an aluminum-based adjuvant to stimulate a more robust immune response

Generally speaking, only when a vaccine candidate enters Phase 3 clinical trials will researchers have a clearer idea as to whether it will provide the desired level of immune protection and safety in a broad sector of the population.