Zika testing
Frequently asked questions answered
As of March 18, 2016, the Public Health Agency of Canada confirmed travel-related cases of Zika virus from Central and South America, and from the Caribbean. It said there is ongoing local transmission in many countries of South Asia, Western Pacific Islands, and South and Central America, including the Caribbean, and Mexico.
This is an ongoing and developing health story, so as I say below, it’s best to speak to a health-care provider for individual questions and concerns as the science and medicine is likely to change.
Pregnant women, and families planning a pregnancy are encouraged to seek personalized medical guidance before travelling and upon returning from an affected country.
Below are the current answers to the most frequently asked questions we are getting at Medcan.
Who should be tested?
Travellers who have developed symptoms resembling Zika infection (pink eye, fever, joint and muscle pain, skin rash and headache) within 72 hours after arrival in, or two weeks after departing from a country where Zika transmission is widespread should be considered for testing. Travellers who do not develop symptoms or whose symptoms have resolved, are not suggested to have testing as it is generally unnecessary because of the scarcity of testing and unproven benefit.
What kind of testing exists?
There are two types of tests.
(1) Molecular. During the initial 10 days post symptoms, polymerase chain reaction (PCR) testing can be used for detection of the genetic material of the virus in blood or urine.
(2) Serological. An individual’s immune system starts to produce antibodies in response to being exposed to the Zika virus and can be detected with a serological test through a blood sample. Antibodies develop in an individual who is symptomatic and can be detected for months to years. This means that a serological test may indicate if a person has been exposed to Zika virus even if symptoms have resolved. However, it is important to recognize that serological testing for the Zika virus is not specific, and may crossreact with other similar viruses. For this reason, serological confirmation may require multiple samples.
Is testing available in Ontario?
All samples collected by a health-care provider are sent to Public Health Ontario that meet the criteria for Zika virus testing are tested locally by the lab for PCR if collected within 10 days of illness. Samples are also tested for chikungunya and dengue, the two viruses similar to Zika. A sample is also sent to the National Microbiology Laboratory (NML) for serological testing depending on travel history and symptoms. Antibody (serological) testing is being performed on all patients and is the only testing available to asymptomatic pregnant women.
Should pregnant woman who travelled to an area with Zika be tested?
Public Health Ontario recommends testing for the following populations:
- Pregnant women with symptoms consistent with Zika virus
- Additional testing is recommended for women whose fetus is suspected of having a congenital anomally and have a history of travel to affected areas
- Following delivery, the newborn has abnormal brain development or microcephaly
Testing will be considered for pregnant women who do not have symptoms but did travel to a country with Zika virus transmission. These patients should consider testing only after discussing risks and benefits with their health-care provider.
The significance of performance of these tests when used in asymptomatic people is unknown at this time, these patients should interpret testing with caution.
Can pregnant women who do not have symptoms with a travel history to (or arrival from) affected countries be tested?
Pregnant women without symptoms and confirmed travel to affected areas can have serological testing through the NML.
What happens if the result is positive?
Patients who test positive should consult with their health-care provider.
What should I do if I am trying to become pregnant and visited an affected area?
Since this is a developing health issue it would be best to speak to your health-care provider as the information on how long the virus will remain in an individual’s system is evolving. Women who are looking to become pregnant may be an advised waiting period to abide by before trying to conceive (at the time of this posting, the recommended period was two months).
What should men do if their partner is trying to become pregnant?
There is some evidence that Zika can be transmitted in semen and therefore, men who have travelled to an affected area should also wait two months after return from a trip to conceive. It is also suggested to use condoms during pregnancy if the women is already pregnant and there has been recent travel to an affected area. Again, since this is a developing health issue, it is recommended to speak to your health-care provider for the most current recommendations.
Does Medcan do Zika testing?
After consultation with a Medcan physician, a blood sample can be obtained for testing if a patient meets the appropriate criteria. We will screen patients and fill out a Public Health Ontario form that is screened by the Public Health lab and sent to the National Microbiology Laboratory for further testing should a patient meet all the criteria for testing. The testing is not performed on-site at Medcan.
Resources
Public Health Ontario: Infectious Diseases, Zika Virus Infection (accessed: March 18, 2016).
Centers for Disease Control and Prevention, Areas with Zika Fact Sheet (accessed March 18, 2016).
World Health Organization, Zika Virus Fact Sheet (accessed March 18, 2016).
