St. Joseph's Health Centre said Friday a patient who was in its emergency department from Jan. 27 to 29 has been diagnosed with the disease.
Two children and three adults in the Toronto area were also diagnosed with measles earlier this week. St. Joseph's did not release any details about the sixth individual, citing the need for patient confidentiality.
The west-end hospital said it worked with public health officials to notify those who may have been exposed to the patient.
"At this time St. Joseph’s has no confirmed measles cases in our facility," said the statement from Dr. Mark Downing, head of the infectious diseases division.
Officials say residents should check their immunization records to make sure they are fully protected.
"We have people who are about 35 to 40 that probably only received one dose," of the vaccine, said Shelley Deeks of
Public Health Ontario.
"So there is a differing level of susceptibility."
Two doses of MMR vaccine provide full protection against mumps, measles and rubella for over 95 per cent of people, according to Toronto Public Health.
Officials say anyone unsure of their immunizations should contact their healthcare provider.