what are the reasons why people live in northern Canada are high risk for TB?

Answer 1

They spend a great deal of time indoors in relatively cramped space during the winter months.

Answer 2

Hi Mary. Today I came across some medical research that may explain this phenomenon. (Don't you just love 'serendipity'!)

Vitamin D deficiency is very common in Canada because of the lack of vitamin D production in the skin during the long winter months. UV sunlight produces vitamin D in the skin and the low angle of the sun in winter blocks all UV sunlight in the north during late fall, winter and early spring.

High levels of vitamin D in the body (not present in most people in the North) activates a component of the immune system called 'cathelicidin' which is needed to eliminate the Mycobacterium tuberculosis! (the organism that causes TB). Low levels of vitamin D do not activate this critical immune response.

This may explain the connection between higher TB risk and living in the north.

I hope this is helpful for you. Best wishes.