Tuberculosis

Q&A: Dr. Elizabeth Rea, Associate Medical Officer of Health, TB Control and Prevention, Toronto Public Health

Outpost: TB is considered low risk for travellers, but with TB endemic in so many countries could this change?

Dr. Elizabeth Rea: A lot of TB in Canada is from people who were born overseas and you could put expats in there—people who live for a long time in an endemic country, then come to Canada and at some point become ill…[But] in the years I’ve been doing this I can think of two [cases of TB in travellers]. One was an adult, who was travelling for months very much off the beaten track—taking local buses, local trains, staying in local guest houses—and became ill with tuberculosis about seven months after returning home.

OP: It’s said you need ‘prolonged exposure’ to a person with active TB to become infected. Can you explain what this means?

ER: TB isn’t nearly as infectious as the common cold or chicken pox. When you look at the transmission of TB, the overwhelming risk is to people who live in the same household, who spend day after day in the same room with the same person [who has active TB].

OP: Is that how you define prolonged exposure?

ER: Yes. Now that said, some people are simply more infectious than others. If someone is very ill their lungs are full of TB and they have more to cough into the air than someone who is not as sick. That does make a difference, because if someone who is extremely infectious happens to be on your bus then yes, in that rare circumstance, on a long bus ride with the windows closed, somebody else might catch it, even though it’s just an eight-hour stretch. But that’s unusual. By and large the biggest risk of catching TB is living in the same household. So for people who are not just travelling, but living and working overseas, TB becomes much more of an issue.

OP: What precautions can travellers take if they’re going to a TB endemic region?

ER: If you’re on a bus try to sit near a window. If you’re sleeping in group accommodations, it’s better to be close to an open window. The greater the ventilation, the lower the risk. And, if you can, try not to be near someone who is clearly ill.

OP: Though a vaccine has existed since 1921, it is not widely used, even for travellers. Why not?

ER: Outside of a handful of situations, like people going to do medical work, it’s not worth taking the vaccine as it only has a 50 percent effectiveness rate against adult forms of TB. Its greatest value is for babies.

OP: If a traveller thinks they may have come in contact with TB, what should they do?

ER: The first thing is not to panic. Tuberculosis operates over months and years, not days and hours. There’s no immediate risk. The general advice is if you’re going to a TB endemic country for a long period—three months or more—get a TB skin test before you go and after you get back. That’ll help sort out if you got infected overseas. A TB skin test may not turn positive until eight weeks after you’ve been exposed. If you do end up taking treatment, or you do become ill with TB, it’s absolutely critical you take the medication the way you’re supposed to—otherwise, you can set yourself up for drug resistance.

OP: Cows can be infected with TB, and people consuming unpasteurized milk are at risk. Travellers often experiment with local food—what advice do you have? [Cow milk] used to be one of the regular routes of infection, so there’s a system of TB control in herds in developed countries. But [bovine TB is] still prevalent in developing parts of the world where there’s heavy reliance on dairy. There’s no reason not to drink the milk, but make sure it’s either pasteurized or boiled.

Note: This information is intended as a guideline only. Always get individualized advice from a doctor or travel health clinic. For more info on TB and travelling, see TB fact sheets from the Public Health Agency of Canada (www.phac-aspc.gc.ca/new_e.html) Also check out globalhealthfacts.org or www.who.int for more statistics from around the world.

This entry was posted on Saturday, October 13th, 2007 at 5:19 pm and is filed under Health. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a comment, or trackback from your own site. Add to del.icio.us.