London, Ont. reports first human case of West Nile virus for 2023

The Middlesex-London Health Unit has reported the first locally acquired human case of West Nile virus (WNV) for the summer of 2023.

According to Public Health Ontario, there have been five probable and confirmed human cases of WNV in Ontario, as well as 222 positive mosquito pools.

“Five mosquito traps have already been identified as WNV-positive in Middlesex-London. This human case emphasises the need for everyone in our community to take precautions,” said Dr. Joanne Kearon, associate medical officer of health with the Middlesex-London Health Unit.

However, 80 per cent of people who become infected with WNV do not get sick, and those who do usually experience mild symptoms. The virus also can only be transmitted to humans by mosquitoes, so human to human transmission is not a risk.

“People who do have symptoms, it’s usually a little bit of muscle aches and a fever, sometimes a rash,” Kearon said. “However, about 1 per cent of people can become quite seriously ill with meningitis or encephalitis, and so become confused, lose their consciousness, have seizures, and end up hospitalised.”

The MLHU says it will continue to conduct surveys and deply control efforts throughout the region. It is also reminding London-Middlesex residents that WNV is still present in the community.

“Some of our tips include staying away from areas where there’s large concentrations of mosquitoes, particularly at dusk and dawn when they’re most active,” Kearon said.

“Using an insect repellent that is shown to be effective, such as with DEET, and wearing long sleeved light coloured clothing can reduce the risk.”

Other steps people can to protect themselves include:

• Ensuring standing water on your property is cleared.
• Regularly rotating water in standing bird baths.
• Covering openings in rain barrels.
• Properly closing and opening backyard swimming pools.