For the first time this year, a mosquito caught in a city trap has tested positive for West Nile virus.

The trap, which was set in lower east Hamilton, tested positive on Aug. 5. Thirty traps are set weekly across the city from June until late fall to assess the risk levels for West Nile.

According to the city, 80 per cent of people who contract the virus have no symptoms. But older adults and people with weakened immune symptoms may get West Nile fever – and some could develop more severe illness including inflammation of the brain.

For any of those infections, if symptoms occur they typically show up from two days to two weeks after being bitten by an infected mosquito, the city says.

As part of prevention methods, the city treats catch basins and stagnant water on public land like ditches and ponds to kill mosquito larvae.

Public health is reminding resident to protect themselves from bites by using bug spray that contains DEET and to remove standing water weekly from property.