The Facts

Zika virus infection is a mosquito-borne viral infection. It is spread by the Aedes species of mosquito, most commonly Aedes aegypti and Aedes albopictus. Aedes mosquitoes also transmit dengue and chikungunya viruses. A mosquito becomes infected when it feeds on the blood of a person infected with the Zika virus. The mosquito is then capable of spreading the virus to other people through its bites.

The Zika virus can cause microcephaly in babies born to women who were infected while pregnant. Microcephaly is a rare birth defect in which the baby's head is smaller than expected, which can be related to problems with brain development. Other possible negative pregnancy outcomes include hearing problems and impaired growth in the newborn.

Zika virus infections have been reported since the 1950s in parts of Africa and Asia, and in the Pacific islands in 2007. In 2015, the Zika virus spread to Central and South America. Aedes species of mosquitos that are known to transmit the Zika virus are not suited to the Canadian climate, so Canadians are very unlikely to contract the infection at home, but cases have been reported of people returning to Canada with Zika infection after travelling to areas where there are Aedes mosquitos and active viral transmission.

Causes

Zika virus infection is spread mainly through bites by Aedes mosquitoes. These mosquitos usually bite during the day. Once a person is infected through mosquito bites, the Zika virus can be found in their blood for a few days, or longer in some people. The virus can then be transmitted to other people when another mosquito bites the infected person.

Less commonly, the Zika virus can be spread through other means, such as sexual contact with an infected person, or through contaminated blood sources such as blood transfusions and laboratory exposure.

Symptoms and Complications

Only about 20% of persons infected with Zika virus experience symptoms, and the symptoms are usually mild. The symptoms last about 2 to 7 days and include:

  • fever
  • headache
  • lack of energy
  • muscle and joint pain
  • physical weakness
  • rash
  • red eye

Hospitalization or death from Zika virus infection is rare. Most people recover without complications, but there have been reported cases of neurological complications such as Guillain-Barré syndrome, an autoimmune disease that can cause muscle weakness and paralysis. The Zika virus can cause microcephaly and other birth defects in babies born to women who were infected while pregnant. Microcephaly is a rare birth defect in which the baby's head is smaller than expected, which can be related to problems with brain development.

Making the Diagnosis

It is important to seek medical attention if you develop symptoms after returning from a region where the Zika virus is being spread. Since the typical symptoms of Zika virus infection can also be due to a number of other causes, Zika virus infection may be misdiagnosed as other conditions such as dengue, yellow fever, chikungunya, or other infections that cause fever and rash. Your doctor may make a preliminary diagnosis of Zika virus infection based on your symptoms and places and dates of travel. Then your doctor can diagnose the virus based on laboratory test results from a blood sample in the first week in the infection.

Treatment and Prevention

There is no specific treatment for Zika virus infection. The symptoms of the infection may be treated – for example, your doctor or pharmacist may recommend taking acetaminophen for fever and headache, as well as rest and fluids to help you recover. Avoid using medications such as ASA (Aspirin®) and other non-steroidal anti-inflammatory drugs (NSAIDs, such as ibuprofen or naproxen) until dengue has been ruled out. Dengue is an infection that causes similar symptoms and is also spread through mosquitos.

Since there is currently no vaccine or treatment for Zika virus infection, it is important to keep from getting bitten by mosquitoes when you're travelling to areas affected by the Zika virus. The following suggestions can help you avoid mosquito bites:

  • Wear light-coloured, long-sleeved, loose-fitting, tucked-in shirts with long pants and a hat.
  • Wear shoes or boots, not sandals.
  • Use mosquito nets over beds and cribs.

If you are pregnant, or planning to become pregnant, avoid travelling to affected areas. If you can't avoid travelling, talk to health care providers about the risk associated with Zika virus infection and birth defects. If you are pregnant and your partner has lived in or travelled to affected areas, talk to your health care provider. They may recommend steps to prevent getting the Zika virus through sex such as using a condom or refraining from sex while you are pregnant.


*All medications have both common (generic) and brand names. The brand name is what a specific manufacturer calls the product (e.g., Tylenol®). The common name is the medical name for the medication (e.g., acetaminophen). A medication may have many brand names, but only one common name. This article lists medications by their common names. For information on a given medication, check our Drug Information database. For more information on brand names, speak with your doctor or pharmacist.