Tuberculosis

The evolution of a bacterium

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• World Health Organization (WH.O. declared TB a global health emergency in 1993

• one–third of the world's current population has been infected with M. tuberculosis

• new infections occur at a rate of one per second

• 2004 statistics: 14.6 million chronic active cases, 8.9 million new cases, and 1.6 million deaths, mostly in developing countries

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• caused by Mycobacterium tuberculosis

• usually attacks the lungs, destroying lung tissue

• can also infect the nervous system, skin, bone, joints…

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Spread• through the air, when people who have the

disease cough, sneeze, or spit – inhalation of a single bacterium can cause an infection

• most infections in human beings will be asymptomatic and latent

• about one in ten latent infections will eventually progress to active disease, which, if left untreated, kills more than half of its victims

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The Difference between Latent TB Infection and TB

DiseaseA Person with Latent TB Infection A Person with TB Disease

• Has no symptoms • Has symptoms that may include: - a bad cough that lasts 3 weeks or longer - pain in the chest - coughing up blood or sputum- weakness or fatigue - weight loss - no appetite - chills - fever - sweating at night

• Does not feel sick • Usually feels sick

• Cannot spread TB bacteria to others • May spread TB bacteria to others

• Usually has a skin test or blood test result indicating TB infection

• Usually has a skin test or blood test result indicating TB infection

• Has a normal chest x-ray and a negative sputum smear

• May have an abnormal chest x-ray, or positive sputum smear or culture

• Needs treatment for latent TB infection to prevent active TB disease

• Needs treatment to treat active TB disease

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Symptoms• symptoms include chest pain, coughing up

blood, and a productive, prolonged cough for more than three weeks

• systemic symptoms include fever, chills, night sweats, appetite loss, weight loss, pallor, and often a tendency to fatigue very easily– as the disease progresses lung tissue is replaced by

scar tissue

• non-pulmonary TB causes all kinds of symptoms

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Risk Factors

• chronic conditions: diabetes, cancer, renal failure, immunosuppression

• low body weight• HIV

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Diagnosis

• usually a tuberculin skin test followed by an X-ray to see if the infection is active

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Life Cycle

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• Following inhalation the bacterium can reside in lung tissue for decades without becoming active

• During a time of immunological stress the bacterium can begin to multiply, forming granulomas and destroying lung tissue, as well as spreading through the rest of the body– Granulomas contain the slowly diving bacteria

as long as immune cells are healthy– Detectable by X-ray

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TB in Canada (2007)

• 1,547 new active and re-treatment tuberculosis (TB) cases (a rate of 4.7 per 100,000 population)

• foreign-born individuals accounted for 66% of all reported TB cases in Canada– Canadian-born non-Aboriginal and Canadian-born

Aboriginal cases made up 11% and 20%, – TB rate in the Canadian-born Aboriginal group continues

to be the highest of the three groups, approximately five times the overall Canadian rate.

• pulmonary TB represents 65% of all reported cases

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Treatment

• people with latent infections will develop TB when it overwhelms their immune system (10%)

• ISOLATION! (forced in North America)

• antibiotics, usually a combination, 6-12 months

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Public Health

• requirement to report• education of patients• isolation

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Current Problems with TB

• Drug resistance: due to improper treatment there are drug-resistant strains of TB

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Prevention

• BCG vaccine is somewhat effective in children (used in South Africa)

• people with latent infections are treated to prevent active TB

• Patient education instructional video