Epidemiology of Tuberculosis Ashry Gad Mohamed Prof. of Epidemiology College of Medicine, KSU

Magnitude of the problem Annually 8 million new cases 3 million deaths 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 10/21/2015Ashry Gad Mohamed

10/21/2015Ashry Gad Mohamed

WHO REPORT 2007 GLOBAL TUBERCULOSIS CONTROL TB is still a major cause of death worldwide, but the global epidemic is on the threshold of decline 1. There were an estimated 8.8 million new TB cases in 2005, 7.4 million in Asia and sub-Saharan Africa. A total of 1.6 million people died of TB, including patients infected with HIV. 10/21/2015Ashry Gad Mohamed

TB prevalence and death rates have probably been falling globally for several years. In 2005, the TB incidence rate was stable or in decline in all six WHO regions, and had reached a peak worldwide. However, The total number of new TB cases was still rising slowly, because the case-load continued to grow in the African, Eastern Mediterranean and South-East Asia regions. 10/21/2015Ashry Gad Mohamed

3. More than 90 million TB patients were reported to WHO between 1980 and million patients were notified by DOTS programmes between 1995 and million new smear-positive cases were registered for treatment by DOTS programmes between 1994 and /21/2015Ashry Gad Mohamed

A total of 199 countries/areas reported 5 million episodes of TB in 2005 (new patients and relapses). 2.3 million new pulmonary smear-positive patients were reported by DOTS programmes in and 2.1 million were registered for treatment in /21/2015Ashry Gad Mohamed

Detection Rate

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." 10/21/2015Ashry Gad Mohamed

Globally, an estimated 9.4 million incident (new) cases of TB in Cases occurred in: WHO South-East Asia Region (55%), WHO African Region (30%), WHO Eastern Mediterranean Region (7%), WHO European Region (5%) WHO Region of the Americas (3%). 10/21/2015Ashry Gad Mohamed

The five countries with the largest numbers of cases in 2008 were: India (1.6–2.4 million), China (1.0–1.6 million), South Africa (0.38–0.57 million), Nigeria (0.37–0.55 million) Indonesia (0.34–0.52 million). Of the 9.4 million new TB cases in 2008, An estimated 1.4 million (15%) were HIV positive; 78% of these HIV-positive cases were in the WHO African Region and 13% were in the WHO South- East Asia Region. 10/21/2015Ashry Gad Mohamed

The total number of new cases of TB is increasing in absolute terms as a result of global population growth. The number of cases per capita is falling. The rate of decline is slow, at less than 1% per year. Globally, the rate peaked at 142 cases per population in In 2008, there were an estimated 140 new cases per population. Incidence rates are falling in five of the six WHO regions. The exception is the WHO European Region where rates are approximately stable. 10/21/2015Ashry Gad Mohamed

Factors contributing to rise of TB occurrence 10/21/2015Ashry Gad Mohamed

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 10/21/2015Ashry Gad Mohamed

Agent Mycobacterium tuberculosis complex M. Tuberculosis M. bovis M. africanum M. microti M. canetti 10/21/2015Ashry Gad Mohamed

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. 10/21/2015Ashry Gad Mohamed

Reservoir Human Cattle 10/21/2015Ashry Gad Mohamed

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 10/21/2015Ashry Gad Mohamed

2-Ingesion of raw milk & diary products. 3-Direct invasion through wounds 10/21/2015Ashry Gad Mohamed

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. 10/21/2015Ashry Gad Mohamed

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. 10/21/2015Ashry Gad Mohamed

Incubation period: 4-12 weeks. 10/21/2015Ashry Gad Mohamed

Diagnosis: No single test is diagnostic in all situations, but complementary techniques should be used to generate complete & rapid information. Tuberculin test to identify infection* Acid fast bacilli smear Culture MMR & X-ray Genotype (DNA fingerprinting)* 10/21/2015Ashry Gad Mohamed

Tuberculin test 0.1ml intradermal hours false negative poor nutrition poor general health overwhelming acute illness Immunosuppression False positive BCG vaccination Other mycobacteria infection 10/21/2015Ashry Gad Mohamed

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. 10/21/2015Ashry Gad Mohamed

Classification of Tuberculosis

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 10/21/2015Ashry Gad Mohamed

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). 10/21/2015Ashry Gad Mohamed

Remain in this stage until treatment is completed Pulmonary Pleural Lymphatic Bone and/or joint Genitourinary Miliary Meningeal Peritonial Others 10/21/2015Ashry Gad Mohamed

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 10/21/2015Ashry Gad Mohamed

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 10/21/2015Ashry Gad Mohamed

Prevention and control

Prevention: Case finding Vaccination Chemoprophylasis Environmental 10/21/2015Ashry Gad Mohamed

Control: Reporting Isolation Concurrent disinfect ion Contact measures Treatment 10/21/2015Ashry Gad Mohamed

Elements of the DOTS Strategy Political commitment Bacteriological diagnostic capacity Regular supply of medications and supplies Directly Observed Treatment Strategy Information system Registries 10/21/2015Ashry Gad Mohamed

Globally, the rate of treatment success for new smear- positive cases in 2007 was 86%, exceeding for the first time, the global target of 85%. Eastern Mediterranean (88%), Western Pacific (92%) South-East Asia (88%) African Region and the WHO Region of the Americas (79% 79%) WHO European (67%) 10/21/2015Ashry Gad Mohamed

Among the 22 high-burden countries, the 85% target of treatment success was met or exceeded in 13 countries, including, for the first time, in Afghanistan. The rate of treatment success was also 85% in Kenya and 88% in the United Republic of Tanzania, showing that countries with high HIV prevalence among TB cases are nontheless able to achieve the targert. 10/21/2015Ashry Gad Mohamed