Toronto's first human rabies case in over 80 years almost certainly was infected outside of Canada.
An official of Toronto Public Health said testing of the strain of the deadly virus taken from the unidentified patient showed it is one known to circulate on the island of Hispaniola.
"The strain results do show that this does seem to be a travel-related case. It is not a strain that's found in Canada," said Dr. Elizabeth Rae, associate medical officer of health for the city of Toronto.
Dr. Rae said testing done by the Canadian Food Inspection Agency showed the rabies strain is one that is found in dogs on Hispaniola, the island shared by Haiti and the Dominican Republic.
Fifteen health-care workers have been offered preventative rabies treatment because they had what a public health assessment determined was a "potential exposure" to rabies through the patient, Toronto Public Health spokesperson Jennifer Veenboer said.
Staff in the health facilities that saw and treated the patient were interviewed to determine if any workers needed to be offered treatment.
A combination of rabies shots and human rabies immune globulin – antibodies taken from the blood of people immunized against rabies – can prevent infection if given quickly enough after the exposure.
Ms. Veenboer said the investigation identified 177 health-care workers who had some interaction with the patient. But it was determined the majority didn't have the type of contact that might have put them at risk of infection.
She couldn't say whether all 15 have agreed to take the treatment. And she would not reveal how many members of the patient's family or circle of contacts have been offered preventative treatment, saying that information is not being released to protect their privacy.
Public health officials won't reveal anything about the individual – not even, at this point, whether the patient is still alive.
But it has been reported that the case is a 41-year-old man who worked in the Dominican Republic for several months before recently returning to Canada.
Dr. Rae said it's still not known how the patient became infected. By the time he was diagnosed, he was too ill to help in the investigation. "There's still no clear exposure story. So in truth we may never know where or how or what animal."
Studying the genome of a rabies virus can disclose a lot about the type animal that carried it and where the animal lived, Charles Rupprecht, chief of the rabies program at the U.S. Centers for Disease Control explained earlier this week.
"You can exquisitely type . . . the virus. And so for example you could tell that it's a bat rabies virus from say the New World or it's a dog rabies virus from Haiti or it's a raccoon rabies virus from North America," Mr. Rupprecht said from Atlanta.
"What it doesn't tell you necessarily is the animal that did the biting."
That's because if an intermediary animal became infected – if a cat was bitten by a rabid bat, for example – and then went on to bite a human, that wouldn't be clear from the tests.
Dr. Rae said the Public Health Agency of Canada has alerted authorities in the Dominican Republic and they are assessing the patient's contacts there to see if they need rabies shots.
She suggested the case is a reminder to people who travel that they should be wary of contact with animals while abroad.
"For a traveller, the kind of general advice would be any animal – don't be touching any animal on your travels," Dr. Rae said.
"The other thing to remember is that you don't really have to have a bite in the sense of a big chunk taken out of your leg. A little nip that saliva could get in, or a lick and you happen to have cuts and scraps on your hand. So it's not always a big dramatic confrontation with an animal that's foaming at the mouth or that kind of stereotype."