Mosquitoes are more than a warm-weather nuisance—they can carry and transmit several dangerous viruses. While Canada is not typically a high-risk region for mosquito-borne diseases, the increasing frequency of international travel raises the potential for these viruses to spread.
This article provides healthcare professionals with the knowledge and tools to recognize and treat common mosquito-borne viruses in Canada to support better patient outcomes.
Understanding Mosquito-Borne Viruses
How Mosquito-borne Viruses Spread
Mosquito-borne viruses are primarily transmitted through the bites of infected mosquitoes. These insects pick up viruses from feeding on the blood of an infected host and then pass the virus on to animals or humans. The transmission process can be swift, making it crucial to understand how these viruses spread to prevent outbreaks.
Why Awareness is Crucial
While Canada has a relatively low incidence of mosquito-borne diseases compared to tropical regions, the risk is increasing due to global travel and climate change. More Canadians are travelling to countries where these diseases are endemic, and warmer temperatures are extending mosquito breeding season. Rising temperatures accelerate mosquito development, biting rates, and the incubation of the disease within a mosquito, meaning that in the coming years, Canadians could face an increased risk of mosquito-borne diseases.
Who is Most at Risk?
Travellers, outdoor workers, and people staying near mosquito breeding sites are at higher risk. Healthcare professionals must be vigilant in recognizing symptoms and providing timely care. Recognizing symptoms early can significantly reduce complications.
Prevention Measures
Patients travelling to regions with a known prevalence of mosquito-borne illnesses should be advised to:
- Use insect repellent containing DEET.
- Wear long, light-coloured, loose-fitting clothing.
- Avoid being outdoors during peak biting periods (between dusk and dawn).
- Sleep in air-conditioned rooms with windows closed when possible.
If sleeping outdoors or in an unenclosed building, use mosquito netting tucked under the mattress.
Mosquito-Borne Viruses To Watch For in Canada
1. Chikungunya
Chikungunya is a viral disease transmitted by Aedes mosquitoes. Though still somewhat rare in Canada, since the spring of 2014, there has been a substantial increase in travel-related chikungunya cases diagnosed across the country. Chikungunya is rarely fatal.
Most prevalent in:
Africa, Asia, tropical parts of the Americas and the Caribbean and Pacific islands.
Symptoms and Clinical Presentation
Chikungunya virus is characterized by sudden onset of fever and severe joint pain, particularly in the hands and feet, which can linger for months. Other symptoms may include headache, muscle pain, joint swelling, and rash on the trunk and limbs. These symptoms usually appear within 3-7 days after being bitten by an infected mosquito.
Diagnosis and Treatment
Diagnosis is usually made through serological tests. There is no specific antiviral treatment; management focuses on relieving symptoms with pain relief medications and supportive care.
Available vaccine? None currently available in Canada, though several are in various stages of clinical investigation.
Learn more about Chikungunya symptoms and management strategies with this accredited course, Chikungunya Essentials: A Guide to Prevention and Management.
2. Dengue
Dengue is another virus mainly transmitted by Aedes mosquitoes. While not endemic to Canada, it is a concern for travellers, with approximately 200-300 cases of dengue diagnosed in Canada each year.
Most prevalent in:
Regions of Africa, Central and South America, the Caribbean, the Eastern Mediterranean, South and Southeast Asia, and Oceania.
Symptoms and Clinical Presentation
Dengue virus symptoms typically include high fever, often accompanied by severe headache, pain behind the eyes, joint and muscle pain, rash, and mild bleeding (e.g., nose or gum bleed). Dengue can progress to severe dengue, which can be fatal.
Diagnosis and Treatment
Diagnosis involves serological tests and PCR. There is no specific treatment, but early intervention with fluid replacement and pain relief can prevent severe complications.
Available vaccine? None currently available in Canada.
3. Malaria
Malaria is not a virus, but a parasitic infection transmitted by infected mosquitoes. Canada sees an average of 488 travel-related cases per year across the country. Malaria can be fatal if not treated urgently and aggressively.
Most prevalent in:
Sub-Saharan Africa, but also found in parts of Oceania, Central and South America, and Southeast Asia.
Symptoms and Clinical Presentation
Malaria presents with flu-like symptoms, including cyclic fevers, chills, sweats, headaches, nausea, vomiting, and body aches. Severe cases can lead to anemia, jaundice, and other life-threatening complications, including seizures, and respiratory and renal failure.
Diagnosis and Treatment
Malaria is diagnosed through blood smears and rapid diagnostic tests. Treatment involves antimalarial medications, with the specific drug regimen depending on the malaria parasite, resistance patterns, and severity of disease. When identified and treated early, almost all cases can be completely cured.
Available vaccine? None currently available in Canada, however there are anti-malarial drugs available. The drugs required vary depending on where patients are travelling. Patients must take anti-malarial drugs before, during, and after travel.
4. West Nile Virus
West Nile Virus is the most common mosquito-borne virus in Canada. It is primarily spread by Culex mosquitoes. The first human case of West Nile Virus infection in Canada was reported in Ontario in 2002. Since 2002, reported cases have varied from 50-1500 annually.
Most prevalent in:
Africa, Europe, the Middle East, North America and West Asia.
Symptoms and Clinical Presentation
West Nile Virus can present with a range of symptoms from mild to severe. Many infected patients will never know they had the disease. Mild cases may involve fever, headache, body aches, and occasionally a skin rash. Severe cases can lead to neurologic diseases such as encephalitis or meningitis, which can be life-threatening.
Diagnosis and Treatment
West Nile Virus is diagnosed through blood tests or cerebrospinal fluid analysis. Treatment is supportive, focusing on symptom management. Severe cases may require hospitalization.
Available vaccine? None currently available.
5. Yellow Fever
Yellow fever is a disease caused by a flavivirus. It gets its name from the yellowing of the skin and eyes that occurs when the virus attacks the liver.
Most prevalent in:
Tropical areas of Africa and South America.
Symptoms and Clinical Presentation
Symptoms of Yellow Fever can take 3 to 6 days to appear and usually include the sudden onset of fever, chills, headache, joint and muscle pain, loss of appetite, abdominal pain, back pain, nausea and vomiting, fatigue, weakness and dehydration. Most patients recover after this stage.
In severe cases, the disease can lead to shock, internal bleeding, jaundice and organ failure. This occurs in about 15 percent of patients, half of whom will die within 10-14 days.
Diagnosis and Treatment
Diagnosis involves serological tests. Treatment is supportive, focusing on symptom management and fever control. Severe cases may require hospitalization.
Available vaccine? Yes. Recommended for healthy persons 9 months of age and older.
6. Zika Virus
Zika virus is a mosquito-borne flavivirus primarily transmitted by Aedes mosquitoes. The virus can also spread through sexual contact and to a fetus during pregnancy. Cases peaked in Canada during the 2016 outbreak, with 468 cases reported.
Most prevalent in:
Tropical and subtropical areas of Africa, the Americas, Southern Asia, and the Western Pacific.
Symptoms and Clinical Presentation
Zika virus infection often results in mild symptoms such as fever, rash, conjunctivitis, muscle and joint pain, malaise, and headache. These symptoms typically last for 2-7 days. When Zika virus infects a pregnant woman, it can cause severe birth defects, including microcephaly.
Diagnostic Methods
Zika diagnosis involves RT-PCR to detect viral RNA in blood, urine, or saliva.
Since 2023, serology testing is no longer routinely recommended due to its lack of specificity for diagnosing recent infection.
Treatment Options
There is no specific treatment for Zika. Symptomatic relief includes rest, fluids, and medications like acetaminophen for pain and fever. Pregnant women require special care due to the risk of birth defects.
Available vaccine? None currently available.
+ + +
Mosquito-borne viruses present a growing challenge in Canada, especially with increased global travel and warming temperatures. Healthcare professionals play a pivotal role in the early detection and management of these diseases.
Stay informed—take this accredited course, Chikungunya Essentials: A Guide to Prevention and Management, available for physicians and pharmacists.
Not a member of MDBriefCase? Join for free today and access hundreds of interactive continuing medical education courses on a variety of health topics.
