Hot sunny days have been few and far between this summer, but despite this Squamish residents are still getting outdoors.
Summer is also a time when mosquitoes are more active. Unfortunately, mosquito bites are a common occurrence when enjoying summer activities.
Occasionally a mosquito bite can have far more serious consequences than an itchy spot. Mosquitoes can help to spread a range of viral diseases.
The best known mosquito-borne disease in North America is West Nile Virus (WNV), which is transmitted between infected mosquitoes and birds. Occasionally, infected mosquitoes transmit WNV to humans and horses.
Most people infected with WNV show no symptoms at all. However, in some cases infection with the virus can result in fever, fatigue and even encephalitis (inflammation of the brain).
In 2003, more than 200 people died from WNV in the United States, as reported to the Centres for Disease Control and Prevention.
Despite the fact that WNV is capable of causing severe illness and death, it is a very simple infectious agent that relies on outside factors to help it replicate and spread.
Like all viruses, it needs to use a host to replicate. WNV is also incapable of moving from host to host by itself and this is where the mosquitoes play their part.
Infected mosquitoes carry the virus in their salivary glands. The virus is transmitted to susceptible birds via mosquito bite. The virus enters the bird's cells, where it uses the cellular machinery to replicate and release new virus particles into the blood stream. When another mosquito bites the infected bird and takes a blood meal, it can be infected, thus continuing the cycle of transmission.
Humans and horses are incidental, or dead-end, hosts for WNV. Both species are able to be infected but neither produces levels of virus in their blood that are high enough to infect a mosquito.
WNV was introduced into North America in 1999 and since then has spread across the States and into Canada. According to the B.C. Centre for Disease Control (BCCDC), the virus was first detected in B.C. in mosquitoes and humans in the Okanagan in 2009. The first bird to test positive was recorded in August 2010.
The BCCDC has a comprehensive surveillance program for West Nile Virus that includes testing mosquitoes, horses, humans and birds for the virus year round. So far this year the news is good - since June 1, no tests have returned positive for WNV in British Columbia.
The spread of WNV relies on many factors, including distribution of mosquito species, bird migration, temperature and rainfall. It will take several years of surveillance to determine whether the virus has become established in Interior B.C.
While mosquitoes in Squamish are unlikely to carry any diseases, it is good practice to avoid being bitten. If you are travelling to the States or further abroad, do a little research to see if there are any mosquito-borne diseases you should be aware of. A little planning can help avoid both itchy bites and illness on your vacation.