Lambton Public Health (LPH) is reporting one more case of the measles.
The health unit said it is working to identify known contacts who may have been exposed.
LPH said anyone who was at the Bluewater Health Petrolia Emergency Department on Monday, April 28 from 2 a.m. to 5:20 a.m. and 7:30 a.m. to 10:20 a.m. may have been exposed.
Anyone who may have been exposed should contact the health unit at 519-383-8331 if you have a severely weakened immune system, or are pregnant and not protected against the measles.
This also applies to anyone born in or after 1970 who is unvaccinated or has only received one dose of the measles vaccine.
Those who may have been exposed are advised to monitor for symptoms for seven to 21 days.
Symptoms of the measles include a fever, red eyes, white spots in the mouth and a red blotchy rash.
The measles virus can live in the air for up to two hours and is highly contagious.
It is spread in the air when someone with the virus coughs, breathes or sneezes.
If you develop symptoms you're urged to contact your health care provider and self-isolate at home.
Further information about the virus can be found on Lambton Public Health's website.
