Norfolk health officials say a sentinel chicken has tested positive for the West Nile virus, which is transmitted by mosquitoes.

The Department of Public Health said mosquito fogging will begin Saturday evening, weather permitting. The city also has started mosquito surveillance and control measures, including storm drain treatments, backyard inspections, trapping and testing.

Most people bitten by an infected mosquito do not get sick, but those who do usually suffer mild, flu-like symptoms. People older than 50 are at a greater risk of serious illness.