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In a measles outbreak, how do we track patient zero?

Toronto Public Health confirmed this week that four cases of measles recently diagnosed in the city have no connection to an ongoing U.S. outbreak. So where did it come from? Health detectives are trying to find out.

Dr. Natasha Crowcroft of Public Health Ontario explains 'very, very careful work'

CBC News ·
Measles is a highly infectious disease, and therefore tracking it to a single source is an extremely difficult and tedious task. (U.S. Centres for Disease Control and Prevention)

Toronto Public Health confirmed this week that four cases of measles recently diagnosed in the city have no connection to an ongoing U.S. outbreak that is thought to have begun at Disneyland in California. 

All four cases appear to be the same strain of the highly contagious virus and are not travel related, suggesting a common link between them that has yet to be discovered. 

So how do health officials track down patient zero when a virus is so contagious you can contract it from simply being in a room where an infected person previously was?

CBC's Metro Morning interviewed Dr. Natasha Crowcroft, chief of infectious diseases at Public Health Ontario — one of the agencies assisting Toronto Public Health with their ongoing investigation — about how investigators are trying to find the source. 

You can listen to the full interview below: 

Metro Morning7:22Tracking Measles
How do you track a disease? Matt Galloway spoke with Dr. Natasha Crowcroft, she is the Chief of Infectious Diseases at Public Health Ontario.

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