Transcript tuberculosis lecture.ppt

Epidemiology of
Tuberculosis
Ashry Gad Mohamed
Prof. of Epidemiology
College of Medicine, KSU
Magnitude of the problem
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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
Ashry Gad Mohamed
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Ashry Gad Mohamed
8/6/2016
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.
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• 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.
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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.
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• 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.
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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."
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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%).
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• 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 SouthEast Asia Region. Ashry Gad Mohamed
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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.
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Factors contributing to rise of
TB occurrence
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Factors contributing to rise of TB
occurrence
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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
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Agent
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Mycobacterium tuberculosis complex
M. Tuberculosis
M. bovis
M. africanum
M. microti
M. canetti
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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
Ashrymultiplier.
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Reservoir
• Human
• Cattle
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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
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• 2-Ingesion of raw milk & diary
products.
• 3-Direct invasion through wounds
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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.
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• 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.
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Incubation period: 4-12 weeks.
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Diagnosis:
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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)*
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Tuberculin test
0.1ml intradermal.
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48-72 hours
false negative
poor nutrition
poor general health
overwhelming acute illness
Immunosuppression
False positive
BCG vaccination
Other mycobacteria infection
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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.
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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
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• 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).
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• Remain in this stage until treatment is
completed
• Pulmonary
• Pleural
• Lymphatic
• Bone and/or joint
• Genitourinary
• Miliary
• Meningeal
• Peritonial
• Others
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• 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
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• 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
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Prevention and control
Prevention and control
Prevention:
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Case finding
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Vaccination
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Chemoprophylasis
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Environmental
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Control:
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Reporting
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Isolation
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Concurrent disinfect ion
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Contact measures
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Treatment
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Elements of the DOTS Strategy
• Political
commitment
• Bacteriological
diagnostic capacity
• Regular supply of
medications and supplies
• Directly Observed
Treatment Strategy
• Information system
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Globally, the rate of treatment success for new smearpositive 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%)
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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.
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