What you need to know about Zika virus

John Ross, MD, FIDSA
John Ross, MD, FIDSA, Contributing Editor

Follow me at @JohnRossMD

Last week, the government of El Salvador gave what might be the strangest public health advice of all time: don’t get pregnant for the next two years. Officials in Colombia, Ecuador, and Jamaica have also warned women to avoid pregnancy, although only for the next several months.

The reason for these unusual recommendations? An outbreak of Zika virus, currently raging in 21 countries in the Americas and the Caribbean, as well as the U.S. Virgin Islands, the Commonwealth of Puerto Rico, Samoa, and Cape Verde.

Until recently, Zika was an obscure virus, confined to equatorial Africa and Asia, and known only to specialists in tropical medicine. It was discovered in 1947, when scientists studying yellow fever in the Zika Forest of Uganda stumbled on a previously unknown virus in a feverish rhesus monkey. In 1958, it was shown that Zika is primarily spread by the bite of the Aedes mosquito. (Zika can also be sexually transmitted.)

The current Zika pandemic began in 2007, when the virus mysteriously appeared in Yap, a remote island in the Pacific Ocean. By 2013, Zika had spread to French Polynesia, an archipelago 5,000 miles away. Over the following year, it spread throughout much of Polynesia, including Easter Island. In early 2015, doctors identified Zika as the cause of an outbreak in the Brazilian state of Bahia. Zika might have arrived in Brazil during the 2014 World Cup, or during the 2014 world championships of Polynesian outrigger canoe racing, which took place in Rio de Janeiro. By now, as many as 1.5 million Brazilians have been infected with Zika.

To date, no new cases of Zika virus have occurred in the United States (although cases have occurred in travelers returning from countries where Zika is endemic). However, according to the World Health Organization, Zika virus is likely to spread to every country in the Americas, except Canada and Chile, which lack Aedes mosquitoes.

Human infection with Zika virus

The vast majority of people with Zika virus are not very sick. In fact, most have no symptoms at all. In the outbreak on Yap, 77% of those with antibodies against Zika in their blood samples (indicating infection with the virus) were never ill.

In those who do get symptoms, the most common finding is an itchy red rash. Fever, headache, joint and muscle pains, and inflamed eyes are also frequent. People typically recover in 2 to 7 days, and death is rare.

If infection with Zika virus is usually mild, why all the fuss? Unfortunately, the virus has two uncommon but severe complications that make it a menace to public health. The Zika outbreak in French Polynesia was associated with a twenty-fold increased risk of Guillain-Barré syndrome. This is an autoimmune disease, often triggered by infections, in which the immune system attacks the myelin lining of nerve cells, resulting in widespread weakness and paralysis. Weakness and paralysis spread from the legs upward. Two-thirds of patients lose the ability to walk, and 25% need to be put on a mechanical ventilator because of weakness of the respiratory muscles. Although most people make a partial or full recovery, 20% are still unable to walk at 6 months after diagnosis.

The other condition linked to Zika virus is microcephaly, a birth defect in which a developing baby’s brain fails to grow to its usual size. Almost 4,000 Brazilian infants with microcephaly have been born since the start of the Zika epidemic, which is about 20 times the expected number. In Paraiba, one of the areas hardest hit by Zika, officials reported microcephaly in one out of every 100 newborns, a rate which is 100 times higher than usual. Hearing and vision problems have also been reported in newborns exposed to Zika in the womb.

Protecting yourself against Zika and other mosquito-borne viruses

Zika infection is not harmful in the overwhelming majority of people. Although the association with Guillain-Barré syndrome is troubling, this is still a rare complication. Epidemics of Zika virus seem to increase the rate of Guillain-Barré syndrome from one out of 100,000 people per year to one out of 5,000 people per year.

As there is currently no vaccine or treatment for Zika, the Centers for Disease Control recommend that pregnant women consider postponing travel to countries where active Zika transmission is ongoing (updated travel advisories may be found here).

Pregnant women going to countries with Zika activity are recommended to protect themselves against mosquito bites by

  • wearing long-sleeved shirts and long pants
  • staying in lodgings with screened-in windows and air conditioning
  • consider using an insecticide-treated mosquito net when napping, as Aedes mosquitoes often bite in the daytime
  • using permethrin-treated clothing and gear (permethrin is probably safe in pregnancy, although data on first-trimester exposure are scanty)
  • using EPA–registered insect repellents; according to the CDC, insect repellents containing DEET, picaridin, and IR3535 are safe for pregnant women when used as directed
  • using protection against mosquitoes throughout the day, and both outdoors and indoors, as Aedes mosquitoes are often found inside.

Although there is currently no Zika transmission in the United States, this may change with the arrival of summer. An American Zika outbreak would likely be on a much smaller scale than the one in Brazil. Greater access to window screens, air conditioners, and insecticide spraying in the United States would probably limit human contact with Aedes mosquitoes.

If there is local transmission of Zika (or dengue or chikungunya, which are also spread by Aedes mosquitoes), in addition to the measures listed above, you should take the following steps to control mosquitoes:

  • Get rid of rain barrels, bird baths, tires, tins, and other sources of standing water. Mosquitoes like to breed in stagnant water.
  • Dump out any water that collects in your garbage cans, and turn pails upside down so they don’t collect water.
  • Inside your home, change water in flower vases every other day, and dump out excess water from flower pot plates. Aedes mosquitoes will breed in your house, if given the chance.
  • Don’t buy a bug zapper. Studies have shown that these do not reduce mosquito bites, and may actually increase mosquito populations by killing off beneficial insects that prey on mosquitoes. And don’t bother with an ultrasound device, as they don’t work either.


  1. John

    Hi there me and my partner are going to mexico in may for the first time, even tho my partner is not pregnant we were thinking of trying for a family in about 2-3 years just wondering if anyone knows how true this is that I heard that the zika virus cam stay in a women’s body or a man’s for upto 3 years? Is this true as I really do not want to cancel my holiday!

    Many thanks

  2. pendi

    in order to avoid mosquito bites, use mosquito nets while sleeping

  3. Kate

    Is there any evidence of women having been infected with the Zika virus and then becoming pregnant years later and having babies with microcephaly? In other words, once a woman has Zika is there always a chance she can have a child with microcephaly even months/ years later after exposure?

    • Paco aragonés lopez

      Tienes que estar en periodo febril, para qué tu cuerpo registre carga suficiente de virus para ser infeccioso, aunque tu cuerpo eliminé carga de virus, cualquier otra picadura de esta misma cepa o de otras diferentes, podría hacer que vuelvas a ser infecciosa y con ello hacerle daño al feto.

  4. Gaurav

    This thing is Getting Serious !

  5. Ed

    My wife and I were in Cartgena Colombia around the time of the zika outbreak there last October. We didn’t know about zika at the time and did not get sick beyond some flu I had. We have been trying to conceive since. Now I am feeling anxious reading all this, especially stuff about zika being in semen for an indeterminate time.. should we get tested ASAP? Or stop trying to conceive?

  6. Stephanie

    I’m taking my family to Tulum Mexico in March. Kids range in age from 17 – 22. My concern is that the Zika virus may lay dormant in the system for years and impact future pregnancies when the kids are ready to have families. Is there any evidence that this may be true. Is there concern in the health field that we don’t know enough about the disease yet to provide a definitive answer?

  7. Carol

    I plan to attend an international conference in Brazil. I am not child-bearing age, but i work in a place pregnant moms visit. Can you tell me if i am infected with the Zika Virus whether i would be a risk to others upon my return. And can you tell me how long the virus remains communicable via mosquito bites after one is infected?

    • Schwartz

      Unless you live in an area where the aedes mosquito is prevelant, you should not worry since the virus is spread by this specific type of mosquito. It’s also important to note that the zika virus leaves your bloodstream after approximately 10 days.

  8. Dorine

    I understand the risk is primarily to fetuses and there is a slight increase, in Gullain-Barre Syndrome. Currently there is not a large reported outbreak in Belize, but my 13 year old daughter is traveling there for 10 days in June. I’m having difficulty finding information regarding Zika risks to healthy teenagers. Does anyone have any concrete date regarding this? Thanks

  9. sydney

    Can the zika virus kill you?

  10. Lynn

    My fiancé and I booked out honeymoon in riveria maya the first week of sept. We plan on trying to conceive early oct. Should we not even go to Mexico and cancel out honeymoon???

    • Shannon Burrs

      I don’t want to alarm you, but I just returned from the riviera maya and I was bit by a Mosquito the first night and a few times after that. I am now on this website due to rashes that have appeared on my body. I am not pregnant yet still concerned.

    • JG

      I was also in the Mayan Riviera in February. We were bit by many mosquitos and my husband came home with flu like symptoms. I inadvertently conceived during that trip yet the CDC will not approve the testing for my husband because they said it was not a high risk area and his symptoms are gone. To be honest I would probably go somewhere else if you can. I am a nervous wreck now and my husband and I can’t even be intimate.

  11. Jill


    I am supposed to go to Orlando Florida in 2 weeks. I am 24 weeks pregnant. I have two conflicting doctor opinions. One has advised me not to go because of all the uncertainties of the virus and another that has said it would be fine to go because I am not traveling out of the country to one of the effected areas. Which one should I listen too? Is this a major concern in Florida?

    • Megan

      I’m 24 weeks pregnant and was just planning a trip to South Carolina, my mom called to tell me not to go. I looked it up and there are Zika carrying mosquitos in SC, although no outbreak cases amongst humans. I’m not going to go, not willing to risk it.

    • Sara

      I’m reading this late, you’ve probably made your decision. Just wanted to let you know there are cases of zika in polk county, which is within an hour’s drive to Orlando. Best of luck to you& your family!

  12. Sharon

    Hi, I had the zika virus in December. After 5 days I was already ok. Do I still have the virus on me? Am I contagious?

  13. Austin Diagnostic Clinic

    insect repellents is a must on your everyday use almost like lotion.

  14. Danielle

    My family traveled to Dominican January 14 for 5 days. 2 days after we got home my 7 yr old son had a fever with muscle aches and a very bad headache, lethargy. We went to doc and left with diagnosis viral. Supportive tx. Next day horrible rash. Appeared as macular papular at first and turned to vesicles. Also in his mouth. Had a np friend look at him and though it was staph secondary to virus. Next day rash worsening called doc and advised to go to er. Er providers seemed stumped. Actually said they were stumped. Several examined him. Then said probably coxsacki disseminated. Just real bad case. Should I worry that it was zika? Very similar symptoms. Should I be concerned with long term issues? Should I worry about guillian barre? Could it reappear as something else (Like shingles).
    Thank you,

  15. Ann Y

    I have MS, so my immune system is already attacking the myelin lining of my nerves. If I contract Zika, does this make me more vulnerable to developing Guillain-Barre syndrome?

  16. Cute diva

    Is it safe to eat fruits from Mexico ?does it have anything to do with zica virus?

    • Daniel

      Infection by food would be an absolut disaster, don´t worry it doesn´t have anything to do. I can tell you this because I´m from Colombia and unfortunately I was infected.

  17. caro

    my husband and i were on our honeymoon in brazil in december. i got the flu (or that’s what we thought it was) when we got back, but otherwise neither of us have been sick. could we still be carrying the virus? we are trying to conceive, so i wouldn’t want to if we may have the virus, but just don’t have the symptoms. thank you.

  18. Mary

    Can the zika virus lay dormant then reactivate- is there any evidence of viral latency?

    • Eduardo Costa

      Hi, Mary.

      Professor Amilcar Tanuri believes that yes, the Zika virus can reactivate. In fact, Prof. Tanuri thinks that this is the only explanation to the serious viral complications both on adults (Guillain-Barré) and fetuses (microcephaly). In any case, I could not find any other research that corroborates Dr. Tanuri’s theory. By the way, this Dr. Amilcar Tanuri worked as Research Fellow in the CDC Atlant, and also as consultant for the WHO. Therefore, it seems that his opinions are well received by the medical community.

  19. Leah

    I just got back from Cayo Coco, Cuba with my partner, and do not believe I’ve got any mosquito bites as I was diligent with spraying bug repellent on my skin and clothes. He did get a couple bites however. We have been trying to conceive for a while now. Should I be tested for Zika? Should he be tested? Any recommendations? So far no symptoms but we just returned today.

  20. Teia

    I am 29 weeks pregnant , so I would like to know if I was to get the zika virus does it still effect my baby development ?

    • Maggie


      Your baby should not be at risk unless you have:

      -Traveled to a Zika infected region during the time of your pregnant.
      -Bitten by a mosquito from an infected region (Americas and Latin America region)
      – Received vaccines while pregnant (microcephaly risk)

      -All of the Zika virus cases in the United States are a result of that individual traveling to a Zika infected region.
      -Although it’s not confirmed, there is a link between getting infected through sexual activity if that person has Zika virus.

    • Maggie

      As far as the Zika virus affecting your baby’s development if you get it, there is always a risk. Not all cases of pregnant women who were exposed to Zika virus had a baby born with congenital birth defects. The WHO, CDC, and PAHO are not entirely sure there is a causation between the two. It wouldn’t hurt to follow the guidelines, though, just to be safe. I’m sure your baby is just fine, don’t fret too much.

  21. JS207


    Are there increased risks associated with Zika virus infection for patients on immunosuppressive medications for autoimmune diseases or post-transplantation?


  22. Marlene

    We traveled to Panama in the beginning of December. We found out on the trip that my daughter was 4 weeks pregnant. This was before all the information about Zika hit the news. She contacted her doctor and told her of the trip. The doctors did not know what to do at the time. Last week she got a call saying that they could test her for the virus in March. I am reading that the virus is only active for a week. Should she take the test for the virus ?
    Any advise on what we need to do?
    What is the likelihood of being infected? I have a cousin who lives in Panama and said very few cases have been reported. Can you offer any advise.

  23. Paula

    In 2013 I developed a rash that started on my face and spread to my trunk, arms and legs. I had started a new inhaler for asthma and I thought this was the culprit. I was treated for presumable Stevens Johnson Syndrome. I had a low grade fever, profound fatigue and ached all over. I developed extreme, excruciating pain in my arms and legs and required re-hospitalization. This all occurred over a 2 week period. I was eventually diagnosed with GBS, AMSAN variant.

    I have not traveled to South America but my boyfriend returned to the USA after living in Brazil several years ago. Is it possible that he could be a carrier and infected me or just coincidental that I contracted GBS? He has no history of Zika to his knowledge.

  24. Mark

    I am a 25 y.o. male planning to do a medical mission in Guatemala next month. I wanted to know if this virus can remain dormant in one’s system. Essentially, if infected, will it affect my ability to have children in the future. I do have unprotected sex with my girlfriend; however, we are not trying to have a baby currently. Is it worth the risk of doing this mission given the uncertain long term ramifications of this virus.

  25. Valerie

    Is the increased incidence of microcephaly limited to Brazil or is it occurring elsewhere as well. Brazil has huge populations of impoverished people in megacities who lack basic sanitation infrastructure. I wonder if its microcephaly rates may be the result of interaction between the virus and exposure to toxic waste, untreated sewage, and or contaminated water, rather than solely to Vika. Should that be the case, other populations might be at considerably less risk for the devastating birth defect.

  26. Joy

    I’m a 50 year old mom, planning to take my 17 year old daughter to Punta Mita this May. Is it safe for us to travel? We have to book travel now. Have no idea what to do. Are there any places in the Caribbean to travel in May?

    • John Ross

      I don’t think we can predict how much transmission there is going to be in any given area in a few months. The mosquito that carries Zika is apparently found in that part of Mexico.

      As stated above, the risks of infection with Zika in non-pregnant persons are low, with the major issue being an increased risk of Guillain-Barre syndrome, possibly as high as 1/5000.

      To put this in perspective, your annual risk of dying in a motor vehicle accident in the United States is 1/10,000.

  27. Jamie

    I swallowed a mosquito on accident recently and am worried about the virus as I’m 29 weeks pregnant. I live in the US but am still concerned. Everything I’ve read mentions bite transmissions only. Should I be worried?

    • John Ross

      I’m going to say no, because there is no evidence that mosquitoes in the US currently carry Zika. As well, Zika and other flaviviruses do not seem to spread by way of the gastrointestinal tract.

  28. Susan

    Is the virus transmitted in any other way (besides being bitten and now, through sexual intercourse). I ask because I’m going for a vacation to Cuba and my daughter (who is NOT going on the trip) is 4 months pregnant….I don’t want to put my unborn grandchild at any risk by contact with my daughter when I return. Thanks,

    • John Ross

      Hi Susan, Zika virus is spread through either mosquito bites or sex. It does not seem to spread through casual contact (i.e., just being around someone with Zika). There are reports of isolation of Zika from saliva, although this is not currently thought to be a probable means of transmission. Dengue virus, which is related to Zika and has been better studied, can also be found in saliva, but dengue doesn’t seem to spread through saliva. If you want to be on the safe side, you should avoid kissing your daughter for 3 weeks after you get back.

  29. Paul T.

    I am going to Mexico later this month. I have congestive heart failure, for which I take various medications including aspirin on a daily basis. If I contract the Zika virus, could it have any adverse impact on my current heart condition? Also, I have heard that you cannot take aspirin to treat the symptoms of Zika. Assuming I develop those Zika symptoms, does that mean that I must stop taking the aspirin that I already take for my heart condition?

    • John Ross

      Hi Paul, Zika virus does not seem to affect the heart directly, as far as we know right now. However, if you have heart issues and get any viral infection, such as flu, the fever and associated higher heart rates may stress the heart. On the other hand, I think your risk is pretty minimal. 80% of people eliminate Zika from their bodies without ever getting sick, and most people who do get sick are not very sick, and usually recover quickly. If you do go, I would recommend taking the measures mentioned here to avoid mosquito exposure. If you did happen to become ill, I would recommend moderate doses of acetaminophen to control fever and achiness.

  30. jim

    so does this virus kill you and if so is it rarely or is a high chance of dying?

    • kitty

      I just read there have been very rare cases of Guillain-Barre syndrome and one recent death associated with it, but it’s very rare. They say 80% of people have no symptoms. It’s mostly an issue for pregnant women as it seems to be associated with a serious birth defect.

  31. Melissa

    If the virus is only thought to remain in the body for up to 3 weeks, why are some countries/organizations recommending that women who are infected and want to become pregnant wait 2 years before doing so?

  32. Bob

    If infected how long is the virus active in the body? Forever? Or does it sort go dormant after the initial infection period with or without the initial symptoms sort of like chicken pox and shingles???

  33. Shaun

    Does the Zika virus stay in your system for life and how long should you wait to get pregnant if infected?

    • John Ross

      Zika only stays in blood for about a week. After the virus is cleared from the blood, it should be OK to get pregnant.

      Updated information on Zika and pregnancy can be found at:


    • Math

      We think the maximum incubation period is 12 days. Let’s say you get infected on the last day of a visit to Brazil. You might go 12 days from then until you start developing symptoms — or no symptoms but having the virus in your bloodstream that could infect the fetus. That period lasts about a week or a little longer.

      That would take you out close to three weeks. We’d expect the virus would be gone from your system by 21 days. Therefore, if you got pregnant later, it’s unlikely that you’d transmit the virus to your fetus.

  34. Enlightening

    What else happened in Brazil recently? Oh, that’s right, they started a Tdap vaccine policy prior to the spike in microcephaly. Brazilian authorities investigating suspected Zika caused microcephaly aren’t finding Zika to be the cause. In one investigation they only found 6 possible infections out of 270 babies. That Tdap vaccineis more than likely causing the spike.

    • kitty

      It’s not just in Brazil, it’s all over the Tropical areas of other Latin American countries, Caribbean too, Africa as well. But let’s not the facts interfere with your opinions.

  35. Will

    I am supposed to be traveling to Guatemala for a mission trip with my school in March. We plan to be there for a week. How high is the risk that one of us gets the Zika virus? And how high is the risk for severe complications?

    • John Ross

      Hi Will, Severe complications with Zika are very uncommon. Most people that are exposed to it don’t even get sick. As you likely do not plan to get pregnant while there, or after your return, the major concern would be Guillain-Barre syndrome. This syndrome occurs in about 1/100,000 people per year, with common triggers being influenza, flu vaccine, Campylobacter infection (a common form of food poisoning), and cytomegalovirus (CMV). Very early information suggests that Zika epidemics may increase the risk of Guillain-Barre, from 5 to 20 times the number of usual cases.

      The CDC website has great information about the health risks of foreign travel. Their Guatemala section is here:


      Note that there are also risks of exposure to malaria and chikungunya in Guatemala, depending on what regions you visit.

    • Edgar Fischer

      I’m from Guatemala, we already have the first case confirmed, if you are planning to stay or travel to the coast or to some areas where temperature is high then you will increase the risk, however if you are staying at Guatemala city, Antigua Guatemala or Quetzaltenango then the risk will be low.

  36. David

    I’m on immunosuppressant medication (Imran) and Remicade for UC, do I have cause for concern? I live in Los Angeles, near the beach.

    • John Ross

      Hi David, More good questions! At present, the natural history of Zika virus in patients on immunosuppressive drugs is not known. There have been no reports of severe illness in immunosuppressed patients out of the millions infected in South America and Polynesia, although this could reflect underreporting and lower use of immunosuppressive drugs in those regions.

      The areas of highest risk for Zika transmission in the United States are Florida, Texas, and Hawaii, which have also seen small outbreaks of other viral infections transmitted by Aedes mosquitoes, such as dengue and chikungunya. Unfortunately, Aedes mosquitoes have recently been detected in California:


      For updated info on Zika in California, I would check out the excellent website of the California Department of Public Health:


  37. Souzie Holmes

    1. How long does the Zika virus remain in your blood?
    2. Does the virus remain in the blood indefinitely, which puts women at risk as and when they conceive?
    3. If Zika is sexually transmitted, will this result in transmitting the disease to the baby?

    • John Ross

      Hi Souzie, Great questions! Our knowledge of Zika is still incomplete, and we need much more information about infection in pregnancy in particular, but I’ll answer based on what we know so far.

      1. How long does the Zika virus remain in your blood?
      Not long. Zika seems to disappear from blood between 2-7 days after infection. In some patients, it may persist in urine and semen for longer (weeks); more research needs to be done on this (see http://wwwnc.cdc.gov/eid/article/21/2/pdfs/14-1363.pdf).

      2. Does the virus remain in the blood indefinitely, which puts women at risk as and when they conceive?
      No, there doesn’t seem to be a carrier state.

      3. If Zika is sexually transmitted, will this result in transmitting the disease to the baby?
      It could, but the vast majority of cases of Zika in pregnancy probably arise from Aedes mosquito bites. Zika infection in the first trimester seems to have the strongest link to microcephaly. If your question is whether Zika infection at the time of conception leads to fetal transmission, we don’t know enough to say, although my guess is that infection this early would be more likely to lead to failure to conceive or miscarriage.

      • Judy

        I’d feel much better if you had said, “no there isn’t a carrier state” rather than “no, there doesn’t seem to be a carrier state.” There are some drugs that seemed safe until it was found out they weren’t.