All the information below is evolving continuously as the science around this current version of Zika virus (Zv) is a work in progress. So, be attentive to updates on information pertaining to,

  1. Human-to-human Zv transmissibility, especially regarding the length of time an individual may carry and pass the virus, though not sick.
  2. Geographic locales at risk for Zv with respect to relevant mosquito population, time of year, and reported cases originated there.
  3. Guidelines for monitoring during and after pregnancy for possible Zv effects on a fetus/newborn.

We are committed to providing accurate information as well as ideas that may help minimize Zv risk even before the science has been conclusive. You should recheck our content here periodically for update, as well as

One thing is clear and will not change. Mosquito bite avoidance in risk areas and forethought and pro-action regarding intimate contact with anyone possibly carrying Zv are undisputed priorities.

DISEASE: A viral infection,

  1. 1 in 5 infected w/ virus become ill; 80% asymptomatic
  2. Symptoms: fever, rash, joint pain, conjunctivitis (red eyes); muscle aches, headache.
  3. Incubation time from exposure to symptoms unknown: likely a few days to 2 weeks.
  4. Illness usually mild: several days to a week duration.
  5. Virus is actively in the blood while the person is ill or asymptomatically infected, and then for 10 weeks or more after (latest knowledge); virus in semen up to 9 weeks post onset of infection.Zika virus (Zv) persists in the placenta for an unknown number of months after maternal infection; it may persist in the brain of even grossly normal-appearing fetuses, even after birth, for an unclear amount of time.
  6. Hospitalization uncommon and death rare.
  7. Microcephaly (head cirucumference > 2 standard deviations below the mean) and fetal neurological damage (including blindness, retardation, and motor dysfunction) occur with increased frequency and severity in ZD-infected pregnant women; microcephaly estimated currently at 1%.
  8. Association with Guillaine-Barre’ Syndrome.
  9. CZS occurs mainly during 1st and 2nd pregnancy trimesters, but can even in the 3rd. Overall rate = 11%
  • CZS occurred in 15% when infection was in 1st trimester.
  • Zv-associated brain abnormalities can occur without microcephaly.


1. Same mosquitoes (daytime feeders, white-striped legs) that cause dengue and chikungunya: illness similar.

  • Aedes aegypti: Mainly S. California, South Texas, Florida (but, at least 30 U.S. states)
  • Aedes albopictus:As far north as New York

2. Body fluids: exposure by intimate sexual contact (vaginally or rectally) with or transfused blood from Zika virus (ZV) infected person.The virus is detectable in breast milk, but transmission has not been reported by that route.

3. Virus has been detected in sperm, urine, and saliva, but it is unknown if the latter two can transmit infectious virus.

4. Mosquitoes that transmit Zv do not live above 6,500 feet (2,000 meters) above sea level.

NOTE: 1. To be at risk for current ZD, you would have had to have been mosquito-exposed in a geographic area with active ZD within the past 2 weeks or have had intimate contact with body fluids of someone who had been in an area with active ZD.

2. If you travel through a Zika-active country, you should maintain mosquito repellents on your skin and clothes (see below, under “Prevention”) while there and for 2 weeks after leaving the Zika zone to prevent passing the virus to the home country mosquito population (since there is an high percentage of Zika infections without symptoms).


  1. American Samoa, Cape Verde, Africa; SE Asia (before current explosive outbreaks*)
  2. Barbados, Bolivia, Brazil, Colombia, Costa Rica, Curacao, Dominican Republic, Ecuador, El Salvador, French Guiana, Guadeloupe, Guatemala, Guyana, Haiti, Honduras, Martinique, Mexico, Nicaragua, Panama, Paraguay, Puerto Rico, Saint Martin, Suriname, U.S. Virgin Islands, Venezuela (check the website for updated information on ZD activity areas)

*May be because this is a novel virus in these “new” areas; in old ZD areas, much of population may be immune from virus prevalence established long ago.

Zika Next Door: Mexico

ZD is present throughout Mexico, except for areas above 6,500 feet (2,000 meters) elevation which is essentially a strip of mountains starting just below New Mexico and curving eastward down the very center of the country ending near the southern border. So, all coastal areas, including Cabo San Lucas Peninsula and the Yucatan Peninsula (Cancun, Cozumel) are risk areas. The ZD mosquitoes do not live above 6,500 feet (2,000 meters). However, in those elevated areas, ZD can still be contracted through sex. Many frequent tourist areas in Mexico are above the mosquito zone.


1. Antibody testing (see item 5 under “Pregnancy”):blood

2. RT-PCR test for viral genetic material (done at CDC):blood, urine, saliva (routinely up to 14 days after symptom onset or possible exposure).

  • Saliva testing increases sensitivity of ZD detection
  • Urine testing increases the time-window of detectable virus: 50% positive at 8 days, 5% at 6 weeks.
  • Serum: 50% of patients have Zika RNA particles 2 weeks after symptom onset; 5% after 6 weeks.
  • Semen: 50% have Zika RNA 1 month after start of illness; 5% after 3 months-rarely after 6 months.
  • Turnaround time for Zv tests results averages 2-3 wks.

Insurers may not cover the costs of testing if there is no associated history of ZD illness and credible Zv exposure.

  • Urine AND Serum PCR (or NAT) tests should be done less than 14d of exposure; if neg, IgM needs to be done. Negative PCR does not R/O ZD.

3. 2-12 weeks after exposure should get IgM antibody test first; if positive, Zv PCR follows; if PCR negative, dengue IgM follows.

  • IgM appears 4d and usually lasts up to 12 wks (but can be longer) post-infxn. NEVERTHELESS, insurers and public health authorities will not agree to IgM being run sooner than 14d after illness onset or last Zv exposure.
  • IgM time to first negative

Median: 122 days (4 mo., 10 days)

Range: 8-210 days (7.5 mo.)

  • Zv IgM can cross-react with IgM of other flaviviruses,



Yellow Fever

West Nile

Japanese encephalitis

Vaccine-generated antibodies: Yellow fever, Japanese encephalitis

TREATMENT (no specific anti-viral medication)

  1. Rest, fluids
  2. Tylenol (acetaminophen or paracetamol) for discomfort, fever; NO aspirin or other ant-inflammatories until rule out dengue or bleeding tendencies.

PREVENTION (no vaccine)

  1. Wear long-sleeved shirts, pants
  2. Use air conditioning, window/ door screens, mosquito bed nets
  3. Empty standing water containers
  4. Repellants*: DEET (> 30%; 20%, if long-acting formulation), picardin (> 20%), IR3535, para-methane-diol products, or oil of lemon eucalyptus extract (> 30%) *If pregnant or breastfeeding, use an EPA-registered agent; DEET and picardin are safe with pregnancy.
  5. Permethrin applied to clothing (or buy pre-treated clothes)
  6. If have had ZD after credible exposure, continue mosquito barriers (Permethrin-treated clothes and insect repellents on exposed skin) for 1 week post-departure from the ZD areas to diminish potential virus spread from you to mosquitoes in your home locale, then to others; 60-80% of Zika Disease can be without symptoms, so you can have the virus in your blood up to a week after last exposure and have no idea of that.
  7. After exposure in a ZD-zone
    • Men should practice safe-sex for at least 6 months; duration of Zika virus in semen unknown.
    • Women should avoid becoming pregnant for at least 8 weeks.
    • Zika virus has been isolated from semen at least 2 weeks after infection onset.
    • Blood may be Zv negative while semen is positive.
    • Current pattern and duration of Zv shedding from genital-urinary tract of men is unknown.
  8. With sexual intercourse, practice barrier and other contraceptive measures while in ZD zones and for 8 weeks (women) or 6 months (men) after departure from them (or abstain).
  9. World Health Organization (WHO) currently strongly recommends pregnant or possibly pregnant women NOT TRAVEL to ZD countries.

ZD AND POTENTIAL/ACTUAL PREGNANCY: ZD infected pregnant women with increased frequency may birth newborns with microcephaly (disproportionately small heads), significant nervous system damage, or have other adverse outcomes of their pregnancies.

  1. In any trimester of pregnancy, postpone travel to ZD areas (the younger the fetus, the worse).
  2. Sexually active women of childbearing age who are heading to ZD areas should,
    • Get a baseline Zika virus (Zv) test if living in or visiting an area where Zv is potentially in local mosquitos.*
    • Get a pregnancy test prior (and possibly after) travel.
    • Practice birth control 2 weeks pre-travel, during, and for 8 weeks after travel exposure (and have a pregnancy test upon return if usual menses are missed).
    • Strictly prevent mosquito bites (see “Prevention”)throughout “mosquito season”.
    • Consult with your gynecologist or an Infectious Diseases specialist.
    • Once pregnant, immediately get a baseline Zv test every month while pregnant.*
    • If the male partner has ongoing exposure to Zv by way of travel, sperm storage for insemination might be considered after the male and female have negative recent Zv tests and mosquito preventive measures are used up to the time of sperm donation.
    • Consider delaying pregnancy conception until off-season for mosquitos (Nov-April in southern Texas); goal is to have most of the 1st pregnancy trimester from Nov-March.
  3. Once the ZD virus is cleared from the blood, a fetus will not be infected (nor is there future risk with pregnancy).
  4. ZD testing should be done on any pregnant woman who has been in a Zika virus zone, between 2-12 weeks post-exposure; within 2 weeks of ZD-like illness.*
  5. There may be false-positive Zika antibody tests (cross-reactions with dengue, West Nile, and yellow fever viruses or yellow fever and Japanese encephalitis vaccines).*
  6. Since Zika virus has arrived in the U.S. and resides in our mosquitoes in the South, childbearing age, sexually active women  need to,
    • Practice strict mosquito bite avoidance (repellents) and arrange their homes for this.
    • Time pregnancy to maximally avoid mosquito season.
  7. While pregnant, if your sexual consort has been in a ZD zone country you should either abstain from sexual intercourse or practice “safe sex” measures for the entire pregnancy.
  8. Post-ZD Pregnancy Monitoring,
    • Ultrasound monitoring for fetal abnormalities; at least one after 28 wks’ gestation (microcephaly best assessed in 3rd trimester)
    • Amniocentesis: after 6 wks from exposure, but no sooner than 21 weeks’ gestation.
    • Newborn babies who are asymptomatic from ZD- confirmed mothers should be monitored for neurological, eye/vision, and hearing problems.
    • Every infant from a pregnancy with possible exposure to Zv should receive postnatal imaging and Zv testing (this was done in only 25% in a 2016-2017 study of Zv cases); consult with your OB-GYN physician on timing.
    • Pregnant women to be tested for Zv at outset and monthly until delivery.*
  9. Pregnancy Timing:
    • Women: Do not attempt pregnancy until at least 6 months post Zika illness symptoms or last risk of exposure (of either sexual partner).
    • Men: Use condoms or abstain from possibly conceiving a child at least 6 months from last Zika exposure.
  10. Zv Testing/ Pregnant Women With Possible Zv Exposure Pre-Conception,*
      • Zika PCR
      • Zv IgM and PCR at least every 3 mo’s
      • Zv PCR on any amniocentesis
      • Every 3 mo’s, counsel pregnant woman on Zv IgM/ PCR limitations.
      • Consider pre-conception IgM baseline.
        • Note: Zv RNA declines over time, so neg test does not R/O recent infxn.


    Based upon the following known facts, we can speculate on the likely implication for Zv in the near future in Texas,

        1. Zv is endemic in Brownsville, TX as of 12/15/16 (and has been along the northern border of Mexico since Dec.,2015).
        2. 80% of Zv infected people have no symptoms.
        3. Zv is transmitted by mosquitoes that are endemic throughout Texas and across the bottom 1/3 – 1/2 of the U.S.
        4. Zv persists in and is transmissible by semen for at least 6 months.
        5. Zv persists in maternal placentas for weeks-months.
        6. Zv can actively infect and persist in the brains of grossly normal-appearing fetuses, even after childbirth.

    *As of 7/24/17, The U.S. CDC is advising pregnant women who have been in a Zv risk area or who have had intimate contact with someone who has to not have ZV testing unless they have had illness consistent with Zv because the number of U.S. cases of Zv infection have been decreasing, which increases the chances of Zv IgM antibody being a false positive test.

    However, whether to continue to test pregnant women according to the above, prior guideline is entirely an individual matter of personal choice and should be discussed with a knowledgeable physician.

    Taking the above into account,

        1. Zv should spread throughout Texas in the upcoming mosquito seasons for at least 2-3 yrs, starting around April; this will likely occur much more rapidly than in 2016 when the virus first showed up as a locally orginated (not travel-related) infection in Miami, FL.
        2. Childbearing age, sexually active women will probably be advised,
          • To always require condom usage with sexual intercourse, unless attempting pregnancy.
          • To routinely use effective mosquito repellents on exposed skin and possibly treat outdoors clothing with permethrin throughout mosquito season, and throughout a pregnancy.
          • To undergo testing (along with their sexual partner) for Zv prior to attempting pregnancy and  monthly throughout pregnancy.
          • Abstain from sexual intercourse or use condoms throughout any pregnancy.
          • Monitor a fetus repeatedly over the course of a pregnancy for development of microcephaly and other abnormalities.
          • Confer with their gynecologist and other appropriate specialists, such as in Neonatology and Infectious Diseases, if a Zv test is positive.

    This may all change if effective vaccine becomes available, but unlikely for the 2017 warm season.



For more information on Zika Virus testing see our testing page.