TORONTO - Toronto has reported its first case of human rabies in 81 years, in an unidentified person who may have become infected during travel outside the country.
Toronto Public Health won't reveal the gender or age of the individual or say where and when the person had been travelling.
Dr. Elizabeth Rae, associate medical officer of health for the city of Toronto said officials in an unnamed country have been notified of the case so that they can investigate whether the person's contacts there need to be given treatment to prevent rabies.
People exposed or believed to have been exposed to rabies are given a combination of rabies shots and human rabies immune globulin, antibodies taken from the blood of people immunized against rabies.
Toronto Public Health is interviewing close contacts of the person and hospital staff who treated him or her before the diagnosis of rabies was made.
"We're still in the middle of those moving numbers. But I can tell you all told, the number of people that even need to be screened to find out if there's a problem is probably going to be under 75," Rae said.
The investigation isn't helped by the fact that it isn't known how the person contracted the rabies virus, which is almost always fatal. By the time the diagnosis was made, the person was too ill to help in the investigation, Rae suggested.
"We do suspect that it's travel related. That part is not entirely clear yet, but it might become clearer in the next couple of days. Because one of the things that the laboratory does is strain typing of the specific (virus)," Rae said. "So what actual strain of rabies is it?"
The Canadian Food Inspection Agency is testing samples from the person to try to identify the strain of rabies, which could indicate which animal the infection came from and where transmission took place.
Charles Rupprecht, chief of the rabies program at the U.S. Centers for Disease Control explained that studying the genome of the particular virus can tell you a lot about what might have happened.
"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," Rupprecht said.
"What it doesn't tell you necessarily is the animal that did the biting."
By that Rupprecht meant that the test won't be able to tell if a rabid bat infected a cat and the cat infected the person. Testing would simply show infection with bat rabies.
Knowing the animal that transmitted the virus is important because rabies cases involving domestic animals like cats or puppies can often result in multiple people being exposed where cases triggered by a rabid bat, skunk or raccoon may be more likely to be solo infections.
The lab work should give investigators a fairly precise picture of where the virus came from, Rupprecht said, noting testing should be able to show -- he used the example of a dog rabies virus -- whether it came from Hispaniola, or Cuba or Latin America.
"All of these rabies viruses have very distinct signatures," he said in an interview from Atlanta.
Rae wouldn't comment on the condition of the infected individual, nor could she say whether the person is being treated with the Milwaukee Protocol, the name given to a treatment regime involving drugs to induce coma and antivirals.
The protocol saved the life of the first person known to have survived rabies infection, a (then) teenager named Gina Giese, who was treated in Milwaukee in 2004. Rupprecht noted the girl recently graduated from university.
A handful of other people have subsequently survived thanks to this treatment. But rabies remains the most fatal infectious agent known to humankind.
This is the first case of human rabies in Toronto since a three-year-old boy was infected in 1931. The last time Ontario reported a case was in 1967, when a four-year old girl in the Ottawa Valley contracted the disease.
There have only been three other human cases of rabies in Canada since the turn of the century: one in Quebec in 2000, one in British Columbia in 2003 and one in Alberta in 2007.
Though generally deadly, rabies isn't easy to catch. Rae said infection occurs when a saliva from an infected animal gets into the body via a break in the skin or through contact with the mucous membranes in the mouth, nose or eyes.
There have been no documented cases of human-to-human transmission of rabies, except where organs or body parts from a person who died of rabies but was never identified as a rabies case were transplanted into other people.
