Zika Virus

What is Zika Virus?

Zika virus infection is caused by a virus which is spread by the bite of an infected mosquito. The illness is typically mild and lasts only a few days. The most common symptoms of Zika virus disease are fever, rash, joint pain, and conjunctivitis (red eyes). The illness is usually mild with symptoms lasting from several days to a week. Severe disease requiring hospitalization is uncommon although there have been increasing reports of a causal link to more severe complications, such as microcephaly, Guillain-Barre syndrome, and other autoimmune and neurological disorders.

Outbreaks of Zika virus disease have been recorded in Africa, the Americas, Asia and the Pacific. Zika virus disease outbreaks were reported for the first time from the Pacific in 2007 and 2013 (Yap and French Polynesia, respectively), and in 2015 Zika virus was reported for the first time in a number of countries in Central and South America, as well as in Mexico and parts of the Caribbean.

In May 2015, the Pan American Health Organization (PAHO) issued an alert regarding the first confirmed Zika virus infection in Brazil. There has recently been a significant increase in number of babies born with birth defects (congenital malformations), such as infants born with an abnormally small head and microcephaly (an underdeveloped brain). The Ministry of Health of Brazil recently identified a possible relationship between Zika virus infection and the increase in the number of microcephaly cases. An investigation to better understand the relationship between the virus infection and increased risk for microcephaly is ongoing.

It is strongly recommended that pregnant women and those considering becoming pregnant discuss their travel plans with a travel medicine specialist or another knowledgeable health care provider to assess their risk. They may wish to consider postponing travel to areas where the Zika virus is circulating in the Americas.  If travel cannot be postponed then strict mosquito bite prevention measures should be followed to protect themselves against bites.

There is no vaccine or medication that protects against Zika virus infection. The Public Health Agency of Canada recommends that all travellers protect themselves from mosquito bites when travelling to areas where the virus is circulating.


Prevention of Zika Virus

Prevention

  • No vaccine exists to prevent Zika virus disease.
  • Prevent Zika by avoiding mosquito bites (see below).
  • Mosquitoes that spread Zika virus bite mostly during the daytime.
  • Mosquitoes that spread Zika virus also spread dengue and chikungunya viruses.

When traveling to countries where this virus or other viruses spread by mosquitoes are found, take the following preventive steps:

  • Use insect repellents
    • When used as directed, insect repellents are safe and effective for everyone, including pregnant and nursing women.
    • Most insect repellents can be used on children. Do not use products containing oil of lemon eucalyptus in children under the age of three years.
    • Repellents containing DEET and picaridin are  first choice topical repellents providing long lasting protection.
    • If you use both sunscreen and insect repellent, apply the sunscreen first and then the repellent.
    • Do not spray insect repellent on the skin under your clothing.
    • Treat clothing with permethrin or purchase permethrin-treated clothing.
    • Always follow the label instructions when using insect repellent or sunscreen.
  • When weather permits, wear long-sleeved shirts and long pants.
  • Use air conditioning or window/door screens to keep mosquitoes outside. If you are not able to protect yourself from mosquitoes inside your home or hotel, sleep under a mosquito bed net.
  • Help reduce the number of mosquitoes inside and outside your home or hotel room by emptying standing water from containers such as flowerpots or buckets.

Transmission of Zika Virus

Through mosquito bites

Zika virus is transmitted to people primarily through the bite of an infected Aedes species mosquito. These are the same mosquitoes that spread dengue and chikungunya viruses.

  • These mosquitoes typically lay eggs in and near standing water in things like buckets, bowls, animal dishes, flower pots and vases. They are aggressive daytime biters, prefer to bite people, and live indoors and outdoors near people.
  • Mosquitoes become infected when they feed on a person already infected with the virus. Infected mosquitoes can then spread the virus to other people through bites.

Rarely, from mother to child

  • A mother already infected with Zika virus near the time of delivery can pass on the virus to her newborn around the time of birth, but this is rare.
  • It is possible that Zika virus could be passed from mother to fetus during pregnancy. This mode of transmission is being investigated.
  • To date, there are no reports of infants getting Zika virus through breastfeeding. Because of the benefits of breastfeeding, mothers are encouraged to breastfeed even in areas where this virus is found.

Possibly through infected blood or sexual contact

  • Zika virus can be sexually transmitted from a man to his sex partners.  The duration of persistence of infectious Zika virus in semen remains unknown.  Sexual transmission of Zika virus from infected women to their sex partners has not been reported.

If you have Zika, protect others from getting sick

  • During the first week of infection, Zika virus can be found in the blood and passed from an infected person to another mosquito through mosquito bites. An infected mosquito can then spread the virus to other people.
  • To help prevent others from getting sick, avoid mosquito bites during the first week of illness.
  • Sexual transmission is reduced by consistent and correct use of latex condoms. Avoid unprotected sexual activity for at least 6 months.

Symptoms of Zika Virus

  • About 1 in 5 people infected with Zika virus become ill (i.e., develop Zika).
  • The most common symptoms of Zika are fever, rash, joint pain, or conjunctivitis (red eyes). Other common symptoms include muscle pain and headache. The incubation period (the time from exposure to symptoms) for this virus disease is not known, but is likely to be a few days to a week.
  • The illness is usually mild with symptoms lasting for several days to a week.
  • Zika virus usually remains in the blood of an infected person for a few days but it can be found longer in some people.
  • Severe disease requiring hospitalization is uncommon.
  • Deaths are rare.

Diagnosis of Zika Virus

  • The symptoms of Zika are similar to those of dengue and chikungunya, diseases spread through the same mosquitoes that transmit Zika.
  • See your healthcare provider if you develop the symptoms described above and have visited an area where Zika is found.
  • If you have recently traveled, tell your healthcare provider when and where you traveled.
  • Your healthcare provider may order blood tests to look for Zika or other similar viruses like dengue or chikungunya.
  • Zika virus testing is not routinely recommended if you do not have symptoms, unless you are pregnant during or within 2 months of returning form travel to a Zika affected area.

Treatment of Zika Virus

  • No vaccine or medications are available to prevent or treat Zika infections.
  • Treat the symptoms:
    • Get plenty of rest
    • Drink fluids to prevent dehydration
    • Take medicines, such as acetaminophen or paracetamol, to relieve fever and pain
    • Do not take aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs), like ibuprofen and naproxen. Aspirin and NSAIDs should be avoided until dengue can be ruled out to reduce the risk of hemorrhage (bleeding). If you are taking medicine for another medical condition, talk to your healthcare provider before taking additional medication.

Zika Virus Infection and Pregnancy

I am pregnant. Should I travel to a country where cases of Zika have been reported?

No.  Pregnant women in any trimester should consider postponing travel to the areas where Zika virus transmission is ongoing. Pregnant women who do travel to one of these areas should talk to their doctor or other healthcare provider first and strictly follow steps to avoid mosquito bites during the trip.

Because specific areas where Zika virus transmission is ongoing are difficult to determine and likely to change over time, the Public Health Agency of Canada (PHAC) and US Centres for Disease Control (CDC) will update this travel notice as information becomes available. Check this website frequently for the most up-to-date recommendations.

Should a pregnant woman who traveled to an area with Zika virus be tested for the virus upon return?

Yes.  All pregnant women returning from a Zika affected area should be offered testing within 2 months of their return regardless of symptoms.  In addition, women, especially pregnant women, who have had unprotected sexual contact with a male partner who has travelled within 6 months to a Zika affected area should be offered testing.
Can a previous Zika virus infection cause someone who later becomes pregnant to have an infant with microcephaly?

We do not know the risk to the baby if a woman is infected with Zika virus while she is pregnant. However, Zika virus infection does not pose a risk of birth defects for future pregnancies. Zika virus usually remains in the blood of an infected person for about a week. The virus will not cause infections in a baby that is conceived after the virus is cleared from the blood.

How long should I wait before attempting to become pregnant after traveling to a country with this virus?

Women who have travelled to Zika-endemic areas should delay pregnancy for at least 6 months.  Men as travellers should delay attempts at conception for at least 6 months.   Couples who have both returned from Zika-endemic areas therefore, should wait 6 months before conception (based on expert opinion.  Studies are on-going).

Men should use condoms or not have sex (vaginal, anal, or oral) during the pregnancy.

Is it safe to use an insect repellent if I am pregnant or nursing?

Yes. Using an insect repellent is safe and effective. Pregnant women and women who are breastfeeding can and should choose Health Canada registered insect repellents and use it according to the product label.


Zika-affected Areas

Where has Zika virus been found?

  • For an up to date list of all countries and territories with active Zika virus transmission, please check the CDC list here.

More  information on Zika can be found on the following websites: