epidemiology and cycle of infection of TB

1. Tuberculosis
BY:
KARIM HUSSEIN 727

2. Tuberculosis is ..
 A very common highly infectious inflammatory disease
caused by mycobacterium tuberculosis and is the
deadliest infectious disease in history.
 It typically affects the lungs but can also affect other
parts of the body.
 Most infections are asymptomatic and latent but about
one in each ten cases progress to active disease.

3. A suspected case should have ..
 prolonged cough (>3 weeks)
 fever,
 decreased appetite, weight loss,
 night sweats,
 and coughing up blood (hemoptysis)

4.  acid-fast bacilli are seen on sputum smear or in other body tissues or
fluids,
 by culturing M. tuberculosis from sputum or other respiratory
specimens,
 Nucleic acid amplification tests are more rapid than culture and
specific for M. tuberculosis. They are also more sensitive than the
acid-fast bacillus smear but less sensitive than culture
 (chest x-ray) radiological abnormalities
 Or using clinical criteria in the absence of microbiologic
confirmation.
 laboratory testing should be performed when feasible to confirm the
diagnosis and to conduct drug susceptibility testing to guide treatment
Confirmation by ..

5. Risk factors ..
 Poverty & crowding
 Malnutrition
 Lack of medical care
 International travelers
 Some diseases “which disables the T-cell mediated immunity”, as:
1. Diabetes Mellitus
2. Chronic lung disease
3. Chronic renal failure
4. Alcoholism
5. AIDS
6. Hodgkin’s lymphoma

6. Descriptive epidemiology ..
1. Person:
 Globally, nearly 9 million new TB cases and approximately 1.5 million
TB-related deaths occur each year.
 Incidence is 40/100,000 new cases yearly in Egypt and <4/100,000 in
usa
 Personal characteristics
 Age & sex
 race
 Genetic and Congenital TB
 Occupation (silicosis-mine workers-health care workers-those under
mental and physical stress)

7. 2. Place:
 TB is a worldwide disease, more prevalent in developing countries
 Most of the estimated number of cases in 2007 were in Asia (55%)
and Africa (31%), with small proportions of cases in the Eastern
Mediterranean Region (6%), the European Region (5%) and the
Region of the Americas (3%).
 The five countries that rank first to fifth in terms of total numbers of
cases in 2007 are India (2.0 million), China (1.3 million), Indonesia
(0.53 million), Nigeria (0.46 million) and South Africa (0.46 million)

8. 3. Time:
 It has a secular trend; since the mid-20th century morbidity and
mortality markedly declined to the verge of eradication.
 nowadays it is an emerging public health problem in developed
countries especially in low socio economic areas d.t:
 Negligence of the TB control program
 Rapid population growth with unmet health and social needs
 Increase of the life expectancy (+chronic cases)

9. • Agent
• Reservoir
• Portal of Exit
• Mode of transmission
• Portal of Entry
• Susceptible host
Cycle of
infection

10. 1. Agent: human type of mycobacterium tuberculosis
2. Reservoir: cases of TB with positive sputum for acid fast bacilli
3. Exit: nose and mouth
4. Mode of transmission: contact droplet from sputum +ve case and a
host
5. Inlet: nose and mouth
6. Susceptible host: depends on personal characteristics and
immunity status as mentioned before.