Toronto Public Health has issued a public warning to alert residents and doctors of an increase in the number of measles cases.

The city health agency says three cases have been reported recently and a fourth is under investigation. Toronto usually sees only three patients with measles a year.

Meanwhile, the Halton Region Health Department on Friday issued a public warning after an Oakville man tested positive for the disease.

The man in his 30s was potentially infectious from March 21 through to March 30, the agency said in a news release.

Measles is a highly contagious disease spread through coughing, sneezing or talking, and direct contact with nasal or throat secretions.

A person with measles is contagious three to five days before the rash appears, until approximately four days after. Click here for more information.

Signs and symptoms of measles include fever, cough, runny nose and red, burning, watery eyes. Other symptoms include white spots on the inner lining of the mouth and a rash that starts on day three-to-five of the illness and can last up to six days.

The Oakville man may have unknowingly spread the disease while visiting the following places during the contagious period:

  • Halton Healthcare Services, Oakville-Trafalgar Memorial Hospital, in the Maternal Child Department, between March 21 and March 26
  • The hospital's Breastfeeding Clinic between 9:30 a.m. and 12 noon on March 29
  • Oak Park Medical Clinic located on Sixth Line in Oakville on the afternoon of March 27 and again on the evening of March 28

The individual also:

  • Visited the Toronto Raptors game at the Air Canada Centre on March 23 (he was in section 320, row 15, seats 20 and 21)
  • Rode the 2:30 p.m. GO train from Oakville Trafalgar Station to Union Station that day, and the 6:43 p.m. train back to Oakville. He was seated in the middle of the train, in the middle of the car, on the second level
  • Visited First Choice Hair Cutters at 2423 Trafalgar Rd. on March 24 in the late afternoon

"The risk for the general public is considered low because most people are immune to measles as a result of past illness and Canada's high immunization rates," the Halton health department said in a press release.

"Although measles is easily transmitted, individuals who have had one dose of the measles vaccine are 85 to 95 per cent likely to be immune, and those who have had two doses of the vaccine are considered virtually 100 per cent likely to be immune," stated Dr. Monir Taha, associate medical officer of health for Halton Region.

Residents born before 1970 are considered to be naturally immune to the disease, Taha said.

Those who develop the symptoms of measles should contact their doctor or Telehealth Ontario at 1-866-797-0000.

With a report from CTV Toronto's Chris Eby