Zika Virus Information

Public Health Ontario has some very good, up to date information on the Zika Virus.  Part of the post is copied here:  The original article and more information is available at Public Health Ontario website


What is Zika virus?

Zika virus is a mosquito-borne virus discovered in 1947 in the Zika Forest of Uganda. Zika virus is a flavivirus closely related to other mosquito-borne viruses such as dengue and West Nile virus.

What are the symptoms of Zika virus infection?

Following the bite of an infected mosquito, symptoms usually appear in 3–12 days, with patients displaying fever, joint and muscle pain, skin rash, conjunctivitis and headache. Zika virus infection is considered a mild illness that generally resolves within 2–7 days; 75–80% of people infected with Zika virus do not display symptoms.

Public health officials are currently investigating an increase in the number of children born with microcephaly (incomplete brain development) as well as the occurrence of Guillain-Barré syndrome in connection with the Zika virus outbreak. Researchers have yet to establish a direct causal relationship between Zika virus infection and microcephaly or Guillain-Barré syndrome.

How can Zika virus infection be treated?

There is no antiviral treatment for Zika virus infection. Treatment options are supportive, including antipyretics (medications to control fever), fluids to prevent dehydration and rest. For additional treatment information see the Committee to Advise on Tropical Medicine and Travel (CATMAT) Canadian Recommendations on the Prevention and Treatment of Zika Virus.

How is Zika virus transmitted?

Zika virus infection is primarily a mosquito-borne disease transmitted by Aedes aegypti and potentially Aedes albopictus mosquitos, which can also transmit dengue fever and chikungunya virus infections. These mosquitoes are not native to Ontario; see the Centre for Disease Prevention and Control for information on the approximate distribution of Aedes aegypti and Aedes albopictus in the United States. It is important to emphasize that to date local transmission of Zika virus infection has not been documented in the continental United States where these two Aedes species are found.

In some cases, transmission may occur from a pregnant mother to her fetus, through blood transfusion or through sexual contact. Further study is required to better understand these potential modes of transmission. Recent reports from Brazil of Zika virus being found in saliva and urine require further study to determine whether these can be sources of transmission.

Where is Zika virus found in the Americas?

Given the evolving understanding of Zika virus transmission in the Americas, readers are urged to refer the Pan American Health Organization (PAHO) map of Zika Virus Activity in the Americas for the latest list of affected countries.

What is the risk of Zika virus infection to Ontarians?

Travel-related transmission: Ontarians travelling to countries where Zika virus is circulating are at risk of infection. The level of risk depends on the time of year they are travelling, the extent of transmission taking place in their destination areas, the degree to which mosquito control measures are being implemented, and the compliance with personal protective measures against mosquito bites.

Local transmission: Based on current information, local transmission through mosquitoes in Ontario is exceedingly unlikely because Aedes aegypti and Aedes albopictus mosquitoes are not native to Ontario and the province’s Aedes species are not known to transmit Zika virus. The potential for local transmission via sexual contact in Ontario is not well-known.

How can Zika virus infection be prevented?

There is no vaccine or immunoprophylaxis (preventive immune treatment) to protect against Zika virus infection. Travellers to affected countries should assess the risks of transmission at their destinations, should try and determine if mosquito control measures are being implemented (if they are staying at a resort  or hotel), and are advised to practice appropriate personal protection measures against mosquito bites during the day and night. Personal protection measures include:

• Covering up by wearing light-coloured pants, long-sleeved shirts and hats.

• Using insect repellant on exposed skin.

• Protecting living areas from mosquito entry.

• Using netting if entry into living quarters cannot be prevented.

See the Committee to Advise on Tropical Medicine and Travel (CATMAT) Canadian Recommendations on the Prevention and Treatment of Zika Virus  and their Statement on Personal Protective Measures to Prevent Arthropod Bites for more detailed information, especially related to approved insect repellants.

CATMAT also recommends that men who have travelled to an area with widespread transmission of Zika virus should use condoms with any partner who is or could become pregnant for two months after their return.


Are there travel advisories for areas affected by Zika virus?

On January 15, 2016, the Public Health Agency of Canada issued a Public Health Notice and a Travel Health Notice concerning Zika virus as confirmed travel-related cases of Zika virus infection from Central and South America have been identified in Canada.

All travellers to affected areas should protect themselves by taking protective measures to avoid mosquito bites. For pregnant women and those considering becoming pregnant, the Committee to Advise on Tropical Medicine and Travel (CATMAT) recommends discussing travel plans with their health care provider and to consider postponing travel to areas in the Americas affected by the Zika virus outbreak. In addition, because the outbreak is expanding and reporting may not be complete or up-to-date, pregnant women may consider postponing travel to affected areas with known Zika virus-transmission, even if cases have not been reported. If travel cannot be avoided, strict personal protective measures should be used.


Who should be tested for Zika virus (ZIKV)?

According to the Committee to Advise on Tropical Medicine and Travel (CATMAT), “testing for ZIKV infection should be considered in the diagnosis of any ill traveller with compatible epidemiologic and clinical history, when symptom onset is within three days after arrival in, to 14 days after departing from, a country where ZIKV transmission is ongoing or widespread. Testing for other similar viral infections and for malaria should also be done as appropriate. Testing is generally not warranted for returned travellers whose clinically compatible illness has resolved, or for those who have travelled and remain asymptomatic, because of the currently limited availability of laboratory testing and uncertain benefit of such testing.”

What kind of diagnostic tests are used for Zika virus?

There are two main types of diagnostic tests for Zika virus: molecular testing (PCR, which detects the genetic material of the virus) and serological testing (which detects antibodies against the virus).

PCR detects the presence of Zika virus genetic material in a blood or urine specimen. During the first 10 days after the onset of symptoms, Zika virus infection can often be diagnosed by PCR detection of the virus in blood or urine.

Serological testing detects the presence of antibodies in blood that a person’s immune system has produced in response to being exposed to the Zika virus. In individuals who develop symptoms, antibodies to Zika virus begin to develop several days after they first become unwell, and will be present for months to years. Therefore, serological test results may indicate if a person was previously exposed to Zika virus, even after symptoms are no longer present. One limitation of serology testing for Zika virus is that these tests may cross react with other viruses in the same family (Flaviviruses), such as dengue virus.  For this reason, serological confirmation of a diagnosis of Zika virus infection requires both acute and convalescent samples from an individual, with confirmation of a four-fold or greater rise in antibodies specific to Zika virus in the convalescent sample.

Is diagnostic testing for Zika virus available in Ontario?

Public Health Ontario’s Laboratory forwards all Ontario specimens that meet criteria for Zika virus testing to the National Microbiology Laboratory (NML) while concurrently doing serological testing of these specimens for chikungunya and dengue, two viruses that can cause illness similar to Zika virus (if dengue genetic material or chikungunya virus genetic material or antibody is detected in a  sample from a non-pregnant patient then Zika virus testing may not be performed).

The NML in Winnipeg has the capacity to do molecular and serological (antibody) testing for Zika virus and offers testing support to provinces and territories. NML will do molecular testing for viral genetic material (PCR) and serological testing for Zika virus for samples collected in Ontario. The type of testing performed is determined by a patient’s individual clinical and travel history. Antibody testing is being performed on all patients.  Zika virus PCR testing is performed on patient samples collected within 10 days of symptom onset. Testing of asymptomatic pregnant patients will be by serology only.

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

Currently, testing for pregnant women who have travelled to one of the affected countries is recommended in the following situations:

• Pregnant women presenting with acute signs and symptoms compatible with Zika virus.

• Additionally, testing should be considered for pregnant women whose fetus is suspected of having a congenital anomaly (with history of travel to affected areas at any point during or immediately before pregnancy).

• Following delivery, if their newborns have microcephaly or abnormal brain development based on ultrasound findings.

Testing may also be considered for asymptomatic pregnant women who were in a country of Zika transmission during pregnancy and never experienced symptoms of Zika virus infection. Such patients considering having testing should discuss the benefits and potential risks of undergoing this testing with their health care providers. The diagnostic tests for Zika virus were primarily developed for use on patients who have recovered from, or are acutely unwell with, Zika virus infection. The performance characteristics of these tests when used in asymptomatic people are not known at this time. If making use of laboratory testing in asymptomatic pregnant patients, results should be interpreted with caution.

What testing  is available for pregnant women with a travel history to (or arrival from) affected countries if they are not showing any signs or symptoms of the disease?

Currently, the NML will perform serological testing for Zika virus for pregnant women with potential Zika virus exposure who did not experience Zika-like symptoms at any time. Molecular testing (PCR) is not recommended on asymptomatic persons after potential exposure as viral genetic material is unlikely to be present in these patients.

What happens if the test result is positive?

Individuals who test positive for Zika virus will be managed by their individual health care provider. Treatment recommendations can be found in the Committee to Advise on Tropical Medicine and Travel (CATMAT) Canadian Recommendations on the Prevention and Treatment of Zika Virus.


According to the Committee to Advise on Tropical Medicine and Travel (CATMAT), “Health care providers should inquire about travel history among all pregnant women. Those who have travelled to a country with ongoing or widespread transmission of ZIKV should be evaluated. Screening of pregnant women should be discussed on a case-by-case basis between the woman and her health care provider. In these discussions, it is important to consider the problems with sensitivity and specificity of currently available diagnostic testing, overall test result interpretation, as well as the prolonged turnaround time of the available tests, which may be problematic in some cases. The decision to test should include consideration of how the results of the screening tests would be used to inform subsequent decisions.”

How should fetuses of women diagnosed with Zika virus infection be evaluated?

According to the Committee to Advise on Tropical Medicine and Travel (CATMAT), “Serial ultrasounds (every 3-4 weeks) are recommended in pregnant women with confirmed or suspected (if testing results are pending) ZIKV infection in pregnancy and for asymptomatic pregnant travellers returning from ZIKV affected areas, to help define risk and counsel the mother. Should central nervous system (CNS) calcifications or fetal microcephaly be noted at ultrasonography of the asymptomatic pregnant returned traveller, then specific ZIKV testing (along with other routine testing) should be undertaken to help define the likely cause of the anomaly.”

What should a woman do if she is trying to become pregnant and has just returned from a Zika-affected area?

As discussed in the Committee to Advise on Tropical Medicine and Travel (CATMAT) statement: “Based on current information on the incubation period and duration of viremia, and the unclear duration of viral persistence in tissues, women wishing to become pregnant should wait at least two months after their return from an affected area before trying to conceive.”

What should men returning from a Zika-affected area do if they have a partner who is trying to become pregnant?

As discussed in the Committee to Advise on Tropical Medicine and Travel (CATMAT) statement: “There is some evidence that ZIKV can persist in semen for more than two weeks, although the true frequency and duration of viral shedding in genital secretions is not known, as a precaution, men who have travelled to an area with widespread transmission of ZIKV should use condoms with any partner who is or could become pregnant for two months after their return.

Until more is known, and based on our experience with other viral infections where shedding in semen may be very prolonged, it is reasonable to consider the use of condoms for the duration of the pregnancy.”