Module 2 TB Disease Transmission & Prevention

Pulmonary Tuberculosis Extra -Pulmonary TB an infectious disease caused by a microorganism called Mycobacterium tuberculosis Tuberculosis

Transmitted from an infected person through aerosolized droplets formed by coughing, sneezing, talking, laughing, or singing Infection is caused by inhalation of droplet nuclei Transmission

Factors affecting Infectiousness: Infecting dose effect - Infectiousness is directly related to the number of tubercle bacilli inhaled Virulence – different strains – ability or capacity of agent to cause a disease Resistance of the person in danger of being infected – dependent by immune system of person The size of the room Ventilation Infectiousness

Pulmonary and laryngeal TB should be considered infectious if the patient – is coughing or – has sputum smears positive for acid fast bacilli, and – is not receiving therapy, has just started, or shows poor clinical response to therapy

Infectiousness Patients are NOT considered infectious if they: – Have received appropriate therapy for 2-3 weeks – Show favorable clinical response to therapy, and – Have negative smear results from sputum specimens

TB Infection takes place when the TB bacteria is inhaled and deposited at the air sacs in the lungs The cilia acts as barrier to protect the body from infection The macrophage at the air sacs help destroy the TB bacilli in healthy persons M. Tb

Most initial infection heals spontaneously as the immune system walls off the organism forming a granuloma. Within granulomas are dormant organisms that can reactivate at anytime 10% lifetime risk of disease once infected Higher risk with immune compromised patients (HIV, diabetes, malnutrition, immunosuppressive therapy, etc.) Natural Course of the Disease (Pathogenesis)

Asymptomatic Negative sputum smears Negative chest x-ray Not infectious Dormant infection Symptomatic Positive sputum smears Positive chest x-ray Infectious Active infection INFECTION INFECTION versus DISEASE DISEASE

Exposure Infection Disease Death 5-10% lifetime risk Untreated, 70% will die in 5 years A TB patient infects persons per year > 90% CURE RATE (w/ DOTS) Healthy Individuals 30% of un- treated TB undergoes spontaneous remission In 90-95% of infected patients, M. tb remains dormant in the body Only active TB patients, especially smear (+) can infect others Person X NotInfectedNotInfected The TB Transmission Cycle

Clinical Features Pediatric TB Adult TB Stage of TB infection Primary tuberculosisPost-primary, secondary or reactivation TB Main diagnostic confirmation Clinical features + history of exposure to a smear (+) case Bacteriology (AFB smear and, if warranted, culture) Serial chest x-ray Bacterial load Low load, low infectiousness High load, high infectiousness Treatment 2-3 drugs4-5 drugs DOT mandatory Yes – by parentYes – by health worker PEDIATRIC versus ADULT TB

Proper and complete drug therapy Proper hygiene Adequate ventilation UV Light HEPA filters Use of masks Proper and complete drug therapy Proper hygiene Adequate ventilation UV Light HEPA filters Use of masks Ways to Reduce Transmission

Cough of 2 weeks or more Chest pains, shortness of breath Fever, loss of appetite & loss of weight, a general feeling of illness & tiredness Sputum production which may be blood-stained Signs and Symptoms

Clinical History and Physical Examination Chest Radiography Tuberculin Skin Test Sputum Microscopy Diagnostic Tools for TB

Sputum examination for AFB or direct sputum microscopy should be the first diagnostic test for patients suspected to have pulmonary TB (PTB). The National TB Program/DOTS recommends that… What is the appropriate initial work-up for TB suspects?

Microscopy is more objective and reliable than chest x-ray Overdiagnosis Diagnosed by x-ray alone Actual Cases

TB does not show a definite pattern on chest x-ray. 40% of patients diagnosed as having TB on the basis of x-ray alone do not have an active TB. “Therefore, chest x-ray is unreliable for diagnosing and monitoring treatment of tuberculosis.” TB does not show a definite pattern on chest x-ray. 40% of patients diagnosed as having TB on the basis of x-ray alone do not have an active TB. “Therefore, chest x-ray is unreliable for diagnosing and monitoring treatment of tuberculosis.” Tomas, K. “Tuberculosis case finding and chemotherapy.” WHO, 1979 Conclusion: Role of Chest X-ray