Zika Virus and International Travel: Who Is at Risk and How to Prevent It?
The Zika virus was first identified in monkeys in Uganda in the 1940s. A few years later, it was found to infect humans. For more than five decades after it was discovered, the Zika virus caused only sporadic outbreaks of illness in Africa, Asia, the Americas, and the Pacific Islands.
However, large outbreaks of Zika virus disease occurred in Yap Island (Micronesia) in 2007, French Polynesia in 2013, and Brazil in 2015, making it a significant public health concern.
Canadians travelling internationally to areas where Zika virus transmission is present are at risk of contracting the infection. Pregnant women are at particularly high risk because the infection can cause serious complications in the developing baby.
There is no vaccine to prevent Zika infection and no specific treatment is available for this disease. This is why knowing the risks, understanding how the infection is transmitted, and taking preventive measures are crucial for protecting your health.
What is the Zika Virus? How Does It Spread?
The Zika virus is a mosquito-borne virus that spreads from person to person through the bite of an Aedes mosquito. These mosquitos are present in tropical and subtropical regions of the world and are active both during the day and night, with peak activity in the morning and late afternoon.
The mosquitos breed by laying eggs in standing or stagnant water, such as buckets, bowls, vases, flowerpots, and animal dishes. A mosquito becomes infected when it feeds on the blood of an infected human. The infected mosquito then spreads the Zika virus to other people that it bites subsequently.
In the majority of people, the virus does not cause any symptoms at all. Some people experience mild illness with symptoms first appearing between 3 and 12 days after the infection and lasting a few days.
Zika symptoms typically include fever, muscle aches, itching, pink eye (conjunctivitis), and skin rash. The symptoms are similar to those caused by other viral infections such as dengue and chikungunya as well as parasitic infections such as malaria.
As a result, it can be difficult to determine the cause of fever-like illness in travellers who have returned from areas with mosquitos and where these diseases are known to be present. In some adults and older children, Zika virus causes post-infection complications such as Guillain-Barre syndrome, a rare neurologic disorder in which the immune system attacks the nerves.
The most common way for Zika virus to spread is through mosquito bites. It can also spread from:
• a pregnant woman to her developing baby
• an infected person to their sexual partner
• an infected person through blood or sperm donation
Zika virus can be found in the semen of infected males for several months. It has also been documented in saliva and tears, and household transmission has been reported, although the mechanism is not known.
The virus is present in breast milk, but the recommendation is for lactating mothers to continue breastfeeding because the risk of viral transmission is outweighed by the benefits.
Zika Virus Prevention and Treatment for International Travellers
There is no specific treatment for Zika virus. People with symptoms should get some rest, drink plenty of fluids, and treat fever and pain with medications.
It is worth remembering that NSAIDs (non-steroidal anti-inflammatory drugs) such as aspirin, Motrin, Advil, and Aleve can cause bleeding complications in people with dengue infection, and these medications should not be used until dengue has been ruled out.
A preventive vaccine for Zika virus has not yet been approved for use, although several clinical trials are underway. Therefore, Zika preventive measures are paramount and are the only way to avoid serious complications. Sexual transmission can be prevented by using condoms or abstaining from sex.
Recommendations for Canadians travelling to Zika-endemic areas vary according to the traveller type and country. All travellers should prevent mosquito bites during and after travel.
The following measures may be useful:
• Cover up with light-colored, long-sleeved shirts, long pants, shoes, and hat.
• Use insect repellants (DEET 20-30% or icaridin 20% for adults and icaridin 20% for children between 6 months and 12 years old). Physical barriers are preferable for infants under 6 months old, but DEET 10% or icaridin 10% may be used if necessary.
• Stay in well-screened, enclosed, air-conditioned areas.
• Use mosquito nets on the bed and on children’s cribs and strollers.
• Apply permethrin insecticide to travel gear and clothing.
The risk of Zika virus infection is higher when:
• Visiting an area with high levels of reported Zika activity.
• Spending time at elevations less than 2,000 m (the mosquito population is substantially less at higher elevations, thereby reducing risk).
• Travelling for longer periods of time to a Zika endemic area.
• Spending time outdoors (well-screened air-conditioned areas such as airports and hotel rooms are relatively safe).
• Spending time in a densely populated area (isolated areas have fewer people to sustain transmission).
Pregnant Women Need Special Precautions to Prevent Zika Virus
Zika virus infection during pregnancy increases the risk of serious harm to the developing baby. The infection is associated with birth defects in the unborn baby, including microcephaly (smaller than normal head and underdeveloped brain), severe neurologic abnormalities, and fetal death.
Therefore, additional recommendations for pregnant women, men and women planning a pregnancy, and men with a pregnant partner are as follows:
Pregnant Women: Expectant mothers are advised to avoid travel to countries with a current Zika outbreak. For travel to countries with a past reported outbreak, pregnant women should discuss Zika prevention and sexual exposure with a healthcare provider. During travel to countries where mosquitos are present (but no Zika has been reported), pregnant women should take mosquito bite preventive measures. In countries where there are no mosquitos, no precautions are necessary.
Men and Women Planning a Pregnancy: Women who could become pregnant during or after travel to a Zika virus transmission area should discuss prevention with a healthcare provider. The recommendation is to prevent mosquito bites and sexual exposure to Zika during and after travel. If a male partner is also travelling to a Zika country, it is advisable to use condoms or avoid sex and wait two to three months after returning before becoming pregnant.
Men with a Pregnant Partner: Men who travel to Zika virus transmission areas with current or past outbreaks should take mosquito bite prevention measures during travel and use condoms or abstain from sex for the duration of the pregnancy.
Top Countries Where Zika Virus is Present
Zika virus is a concern in the Caribbean, Central America and Mexico, South America, South Asia and Southeast Asia, the Pacific Islands, and West, Central, and East Africa.
For international travellers from Canada, the majority of Zika infections are acquired in the Caribbean and South and Central America.
Before travelling to areas where Zika virus is present, talk to your local travel clinic about precautions and preventive measures. This is especially important for pregnant women, women who could become pregnant during or shortly after travel, and men with pregnant partners.
History of Zika Virus
The Zika virus was first discovered in 1947 in a rhesus monkey in the Zika Forest of Uganda. The virus was named after the forest where it was first identified.
For several decades after its discovery, Zika virus was considered to be a relatively minor public health concern, with occasional outbreaks occurring in Africa and Asia. The first reported outbreak of Zika virus in humans occurred in the Pacific island nation of Yap in 2007.
In 2015, a large and rapidly spreading outbreak of Zika virus occurred in Brazil and quickly spread to other countries in South and Central America and the Caribbean. This outbreak was linked to a significant increase in the number of cases of microcephaly, a birth defect characterized by an abnormally small head and brain, in newborn babies.
In response to the rapidly spreading outbreak, the World Health Organization declared the Zika virus to be a public health emergency of international concern in 2016. This declaration led to increased efforts to control the mosquitoes that transmit the virus and to develop new treatments and vaccines.
Since the initial outbreak in Brazil, the Zika virus has continued to spread to other countries, with sporadic outbreaks occurring in different parts of the world. Despite ongoing efforts to control the spread of the virus, it continues to pose a significant public health challenge, especially in developing countries with limited resources for controlling mosquitoes and treating infected individuals.