Epidemiology of Tuberculosis Prof. Ashry Gad Mohamed MBChB, MPH, DrPH

Objectives 1. To perceive the magnitude of global tuberculosis problem. 2. To understand the cycle of infection of tuberculosis. 3. To understand methods of prevention and control of tuberculosis.

Magnitude of the problem Globally, 9.2 million new cases 1.7 million deaths from TB, 2006 of which 0.7 million cases and 0.2 million deaths were in HIV-positive people. 95% from developing countries 19-43% of world population is infected Between G. One billion will get infection 200 million get sick 35 million will die

Tuberculosis (TB) remains one of the world’s deadliest communicable diseases. In 2013, an estimated 9.0 million people developed TB and 1.5 million died from the disease, of whom were HIV-positive. TB is present in all regions of the world

Of the estimated 9 million people who developed TB in 2013, more than half (56%) were in the South-East Asia and Western Pacific Regions. A further one quarter were in the African Region, which also had the highest rates of cases and deaths relative to population. India and China alone accounted for 24% and 11% of total cases, respectively.

TB is slowly declining each year and it is estimated that 37 million lives were saved between 2000 and 2013 through effective diagnosis and treatment. About 60% of TB cases and deaths occur among men

Almost 60 per cent of TB cases worldwide are now detected, and out of those, the vast majority are cured. Over the past decade, 26 million patients have been placed on effective TB treatment thanks to the efforts of governments and a wide range of partners. But the disease still kills 4400 people every day."

TB in Saudi Arabia During the period there were a total of 64,345 reported TB cases. Of these 48% were Non-Saudis. TB annual incidence rate ranged between 14 and 17/100,000. For Saudis, the rate ranged between 8.6 and 12.2/100,000.

Non-Saudis had 2-3 times higher incidence. Disease trend was rising over the first 10 years( ) then it started to fall slightly. The incidence increased with age, but only people older than 45 years showed a declining trend. Regional variations were observed. Makkah and Jazan regions had the highest incidence rates. Disease trends were rising over the last 10 years in Makkah and Central regions.

Factors contributing to rise of TB occurrence HIV/AIDS 15% of deaths among AIDS patients due to TB. Poorly managed TB programs Wrong treatment regimen and inconsistent or partial treatment lead to multidrug resistant TB (MDR-TB). Movement of people Global trade, traveling and migration

Agent Mycobacterium tuberculosis complex M. Tuberculosis M. bovis M. africanum M. microti M. canetti

Tuberculosis Bacillus Tuberculosis Bacillus Bacillus is thin, somewhat curved, from 1 to 4 microns in length, with a complex cellular wall (lipid core) responsible for its characteristic coloration (acid-alcohol-resistant). Susceptible to sunlight, heat and dryness. Strictly parasitic and airborne; slow multiplier.

Reservoir Human Cattle

Modes of transmission 1-Air-borne droplet nuclei 1-5 μ m in diameter. remain airborne for long times. Factors determining the probability of infection No. of organisms expelled Conc. of organisms in air Length of exposure Immune status of exposed person

2-Ingesion of raw milk & diary products. 3-Direct invasion through wounds

Immune System Response Bacteria invades lung tissue White cells surround the invaders and try to destroy them. Body builds a wall of cells and fibers around the bacteria to confine them, forming a small hard lump.

Bacteria cannot cause more damage as long as the confining walls remain unbroken. Most infected individuals never progress to active TB. Most remain latently-infected for life. Infection progresses and develops into active TB in less than 10% of the cases.

Incubation period: 4-12 weeks.

Diagnosis: No single test is diagnostic in all situations, but complementary techniques should be used to generate complete & rapid information. 1-tuberculin test to identify infection* 2-Acid fast bacilli smear 3-Culture MMR & X-ray Genotype (DNA fingerprinting)*

Tuberculin test 0.1ml intradermal hours false negative poor nutrition poor general health overwhelming acute illness Immunosuppression False positive BCG vaccination Other mycobacteria infection

Interpretation: On the basis of sensitivity, specificity and the prevalence of TB in different groups three cut points have been recommended for defining positive tuberculin reaction. 5mm. 10 mm. 15 mm.

Classification of tuberculosis Based on exposure history, infection & disease. Class 0: No history of exposure Negative tuberculin test (no infection) Class 1: History of exposure Negative tuberculin

Class 2: Positive tuberculin (latent infection) Negative X-ray Negative bacteriology & radiol. Class 3: Patients with clinically active TB Whose diagnostic procedures were completed (positive clinical, bacteriological or/and radiological of current TB).

Remain in this stage until treatment is completed Pulmonary Pleural Lymphatic Bone and/or joint Genitourinary Miliary Meningeal Peritonial Others

Class 4: -Not clinically active TB -Receiving treatment for latent infection -Completed previously prescribed -course of chemotherapy -Abnormal stable radiol. With negative bacteriology and positive tuberculin

Class 5: Tuberculosis suspect -Clinically active disease has not been ruled out. -Persons not adequately treated in the past. -Patient should not remain in this stage more than 3 months

Prevention and control Prevention: Case finding Vaccination Chemoprophylasis Environmental

Control: Reporting Isolation Concurrent disinfect ion Contact measures Treatment

Elements of the DOTS Strategy Political commitment Bacteriological diagnostic capacity Regular supply of medications and supplies Directly Observed Treatment Strategy Information system Registries

Two potential barriers The first is multidrug-resistant tuberculosis (MDR-TB), Given limited laboratory and treatment capacity, countries project they will provide treatment only to an estimated 10% of people with MDR-TB worldwide in The second threat to continued progress is the lethal combination of TB and HIV, particularly in Africa