PrintStraight from the Expert
Tuberculosis – Dr. Ted Marras
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| Dr. Ted Marras, Respirologist, Tuberculosis Clinic |
World Tuberculosis Day was March 24. We talked to Dr. Ted Marras, a respirologist in the UHN TB Clinic, to find out more about the disease.
Why are we hearing about TB lately? Is it really on the rise in Toronto?
We are hearing more about TB because new research has not only shown that TB is very common in homeless people and shelter residents, but also that the infection has much more serious consequences among these groups. This is probably because, among homeless people, health care issues are neglected until they are very advanced; other diseases may also be left untreated, complicating the TB treatment and recovery even more.
Thankfully, TB rates in Toronto are falling. Media reports bringing the disease to our attention are a good thing. If we’re not reminded about TB, we may fail to detect cases early, leading to more transmission and increasing rates.
How concerned should people be about TB in Toronto?
The rates of TB in Toronto, although higher than the rest of Ontario, remain much lower than in most parts of the world. In addition, our excellent health care system facilitates effective treatment and positive outcomes in the majority of cases.
How widespread is TB globally?
The frequency of active TB disease varies by location. Globally, the rate of active TB disease is 137/100,000 people (9.4 million new cases in 2009). The highest rates in the world are in Africa. In Canada, the rate is about 5/100,000 per year. Rates in Toronto are 12/100,000 per year.
What exactly is TB and how is it spread?
Tuberculosis is an infection, usually involving the lungs, but may also involve any other part of the body. Most people who have been infected with the germ that causes TB never get sick with it; this is called “latent” infection and is completely asymptomatic. Unfortunately, the germs are not killed by the immune system, and approximately 10% of people who get infected with TB germs develop tuberculosis disease (“active TB”).
TB is spread between people. A patient with “active TB” in the lungs who is coughing will expel tiny droplets that contain TB germs. The closeness and duration of contact between people increase the chance of spread. Patients with more severe TB lung disease are also generally more likely to pass it on to others because they tend to cough up more TB germs. Patients with latent infection are not infectious and cannot spread TB.
Who is most at risk of contracting TB and why?
TB can infect anyone. The highest risk period for developing active disease is within the first two years of exposure. The people at greatest risk of developing active disease are those with immune suppression, including HIV infection and patients receiving certain immune suppressive drugs. Diabetes, kidney failure and certain cancers are also important risk factors.
What can be done to prevent its spread?
Patients with active TB should be isolated from others until the disease is adequately treated. People with unexplained and persistent cough (especially with phlegm that may be bloody, fevers, unexplained sweats and weight loss) should be assessed by a physician. The presence of these symptoms in someone who has recently lived in an area with high levels of TB, should be assessed very carefully for possible TB.
What are the symptoms?
Symptoms include lung symptoms (cough, sputum or phlegm that may be pink or bloody), generalized symptoms (fatigue, weight loss, fever, unexplained sweating) or, less commonly, symptoms related to TB in other parts of the body. Because the symptoms can be nonspecific, a useful feature is that the symptoms are persistent, for weeks or longer.
How is it treated?
Active TB disease is usually treated with a combination of four antibiotics initially. The number of drugs may be reduced depending on whether the particular strain of TB is susceptible to standard TB drugs. Treatment is monitored closely to ensure there is improvement in the TB and also to detect important side effects. The treatment is continued for at least six months, but sometimes much longer.
Latent TB infection is treated only in the cases when the potential benefit of treatment is thought to outweigh the possibility of adverse effects. Remember that people with latent TB infection feel completely well, are not infectious, but have a chance of developing active TB disease at some time in the future. Latent TB infection is treated with one drug, generally for nine months, sometimes less, depending on the drug that is used.
Are there alternative treatments for drug-resistant TB?
Approximately 15% of cases of TB diagnosed in Toronto have some degree of drug resistance. However, “multi-drug resistant” TB (MDR-TB - TB resistant to the two most important TB drugs) occurs in only about 2% of cases in Toronto.
Access to different TB drugs, expertise in TB treatment and good medical monitoring are all reasons for our high success rate for treating MDR-TB and we are fortunate in Toronto to have all of these criteria. Thankfully extensively drug resistant TB (XDR-TB – TB resistant to two additional very potent TB drugs) remains extremely rare in Toronto. XDR-TB treatment is far more complex with often poor outcomes.
Are there any special considerations for travellers?
Generally, travel is not a major concern among Canadians since most travellers don’t spend time in situations where there is a high risk of transmission. Canadians who travel abroad and spend extended periods (ie. months) in close contact with local people in areas with high TB rates, especially if they have immune suppression or are children under five, should consider consulting with a physician before they travel. In some instances, TB testing may be appropriate.
