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

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 2000-2020 G. One billion will get infection 200 million get sick 35 million will die

04/20/23Ashry 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

195 000 patients infected with HIV.


• 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.


3. More than 90 million TB patients were reported to WHO between 1980 and 2005.

• 26.5 million patients were notified by DOTS programmes between 1995 and 2005.

• 10.8 million new smear-positive cases were registered for treatment by DOTS programmes between 1994 and 2004.


• 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 2005.

• and 2.1 million were registered for treatment in 2004.


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."


Globally, an estimated 9.4 million incident (new) cases of TB in 2008.

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%).


• 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.


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 100 000 population in 2004. In 2008, there were an estimated 140 new cases per 100 000 population.

Incidence rates are falling in five of the six WHO regions. The exception is the WHO European Region where rates are approximately stable.


Factors contributing to rise of TB occurrence


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 Tuberculosis BacillusBacillus• 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

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.

• Tuberculin test to identify infection*• Acid fast bacilli smear• Culture• MMR & X-ray• Genotype (DNA fingerprinting)*


Tuberculin test

0.1ml intradermal. • 48-72 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

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 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 ofmedications and supplies

• Directly Observed Treatment Strategy

• Information system

Registries


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%)


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.


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

Documents

incident new cases of

cent of tb cases

tb patients

total number of new

number of cases

new patients

new smearpositive cases

hivpositive cases