Ottawa Public Health confirms second human case of West Nile virus in city this year

In this Sept. 8, 2010, file photo, a mosquito is held up for inspection at a research institute in Portland, Maine. (AP Photo/Pat Wellenbach, File)

Ottawa Public Health is reporting a second person has contracted West Nile virus in the city this year and raising the alarm over a confirmed case of eastern equine encephalitis virus (EEEV) in a horse.

OPH confirmed the first case of West Nile virus in a person in July.

“Both diseases spread to humans through mosquito bites,” the health unit said in a statement.

There were no confirmed cases of West Nile Virus transmitted to humans in Ottawa and 54 in Ontario last year.

OPH's West Nile virus mosquito trapping and lab testing program has confirmed 14 positive mosquito pools, a "notable" increase over recent years.

Most people will not develop any symptoms if infected, but about 20 per cent may experience flu-like symptoms, including fever, headache, muscle aches and, possibly, a rash.

The risk of more serious illness occurs in less than one per cent of infections, but increases with age, with older adults, the elderly and people with weakened immune systems being most at risk.

The health unit is reiterating calls for residents to protect themselves from mosquitoes after a horse in Ottawa recently tested positive for both EEEV, also known as Triple-E virus, and West Nile virus. Another horse tested positive for EEEV in Lanark County last month.

EEEV is normally transmitted between wild birds and mosquitoes but can occasionally infect horses and, rarely, humans through infected mosquitoes’ bites. Humans do not get infected through horses or other humans.

"Whereas mosquitoes that carry West Nile virus are most commonly found around homes in urbanized areas, the mosquitoes that carry EEEV are usually found close to swampy hardwood forests. Horses can be protected by a vaccine against EEEV but there is no vaccine for humans," OPH said in a news release.

Human infections with EEEV have been rare in Ontario. Historically there have been three human cases of EEEV in Ontario, the most recent reported in 2022.

There have been no human transmissions of EEEV reported.

"Although rare, the disease is of concern because, like West Nile virus, it can cause a serious neurological disease and even death. Anyone who lives, works, or participates in outdoor activities in or around wooded swampy areas where the virus is active can be at risk," OPH said. 

The health unit is advising residents to take precautions to protect themselves from mosquito bites and prevent mosquito breeding, using the following tips:

• Applying a Health Canada-approved mosquito repellent containing DEET or icaridin to exposed skin and clothing
• Protecting yourself, especially between dusk and dawn, when mosquitoes are most active, and any time you are near shady, bushy, or wooded areas
• Wearing light-coloured, tightly woven, loose-fitting clothing, such as long pants, a long-sleeved shirt, shoes and socks, to protect exposed skin
• Making sure all windows and doors in your home have screens that are in good condition
• Removing, or emptying once per week, standing-water sites around your home, such as bird baths, toys, flower-pot saucers, swimming-pool covers, old tires, wheelbarrows, buckets, and cans
• Keeping all openings to rain barrels covered with screen mesh at all times