Epidemiology of tuberculosis

EPIDEMIOLOGY OF TUBERCULOSIS

Presented by :Dr SaundaryaGuided by :Dr Hemant Kumar

Department of Community Medicine AJIMS &RC Mangalore ,Karnataka

04/18/2023 2A Tribute of Robert Koch

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INTRODUCTION Tuberculosis (TB) -

Infectious bacterial disease caused by Mycobacterium tuberculosis - most commonly affects the lungs.

Transmitted from person to person via droplets from the throat & lungs of people with the active respiratory disease.

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HISTORYConsumption, phthisis, scrofula, Pott's

disease, and the White Plague are all terms used to refer to tuberculosis throughout history.

It is generally accepted that the microorganism originated from other, more primitive organisms of the same genus Mycobacterium

Researchers theorize that humans first acquired it in Africa about 5,000 years ago

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HISTORY

Hippocrates, in Book 1 of his Of the Epidemics, describes the characteristics of the disease: fever, colorless urine, cough resulting in a thick sputa, and loss of thirst and appetite

He notes that most of the sufferers became delirious before they succumbed to the disease

Hippocrates and many other at the time believed phthisis to be hereditary in nature

Aristotle disagreed, believing the disease was contagious.

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CONT.

1865- Jean-Antoine Villemin proved TB is contagious

1882- Robert Koch discovers M.tuberculosis

1884- First TB sanatorium established in U.S

1943- Streptomycin- a drug to treat TB was discovered

1943-1952- Two more drugs discovered to treat TB – INH & PAS

Mid 1970s- most TB sanatoriums in U.S closed

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FATHER OF MODERN TB EPIDEMIOLOGY

Karel Styblo, MD, (1921 – 13 March 1998) was born in Czechoslovakia.

Internationally renowned for his work with tuberculosis (TB) - medical advisor to the Royal Netherlands Tuberculosis Association - director of the International Union Against Tuberculosis and Lung Disease (IUATLD) in Paris from 1979

Known as the “Father of modern TB epidemiology" and the "father of modern TB control"

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BURDEN

GLOBALLY

In 2013, mortality of TB including HIV was 16 per lakh cases

Mortality of TB excluding HIV was 5 per lakh cases

Prevalence of TB was 159 per lakh

Incidence of TB was 80 per lakh

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Magnitude of the Problem

Source: WHO Geneva; WHO Report 2008: Global Tuberculosis Control; Surveillance, Planning and Financing

Global annual incidence = 9.1 million

India annual incidence = 1.9 million

India is 17th among 22 High Burden

Countries (in terms of TB incidence rate)

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INDIAIndia is the highest TB burden country in the world & accounts for nearly 1/5th (20 per cent) of global burden of tuberculosis, 2/3rd of cases in SEAR.

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Contd… Estimated incidence

◦1.96 million new cases annually◦0.8 million new smear positive cases annually◦75 new smear positive PTB cases/1lakh

population per year Estimated prevalence of TB disease

◦3.8 million bacillary cases in 2000 ◦1.7 million new smear positive cases in 2000

Estimated mortality◦330,000 deaths due to TB each year◦Over 1000 deaths a day◦2 deaths every 3 minutes

Prevalence of TB infection ◦40% (~400m) infected with M. tuberculosis

(with a 10% lifetime risk of TB disease in the absence of HIV)

Estimated Multi-drug resistant TB◦< 3% in new cases◦12% in re-treatment cases

TB-HIV◦~2.31 million people living with HIV (PLWHA)◦10-15% annual risk (60% lifetime risk) of

developing active TB disease in PLWHA◦Estimated ~ 5% of TB patients are HIV infected

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EPIDEMIOLOGICAL DETERMINANTS

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Goal 6: “Combat HIV/AIDS, malaria and other diseases”◦Target 8: “By 2015, to have halted and begun

to reverse the incidence of malaria and other major diseases…” Indicator 23: between 1990 and 2015 to halve

prevalence of TB disease and deaths due to TB Indicator 24: to detect 70% of new infectious

cases and to successfully treat 85% of detected sputum positive patients

Millennium Development Goals

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AGENT FACTORS Agent

Mycobacterium tuberculosis - facultative intracellular parasite, ingested by phagocytes & resistant to intracellular killing

Source of infectionHuman - human case positive

for tubercle bacilli & who has either received no treatment or has not been fully treated

Bovine - infected milk

CommunicabilityPatients are infective as long as

they remain untreated

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HOST FACTORS Age, Affects all ages

In India, 0-14 age group – 2% 15-24 age group - 20%

Sex,More prevalent in males

Nutrition,Malnutrition – predisposes to TB

Immunity,Man has no inherited immunity against TB

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Social factorsTB is a social disease with medical aspects, also

known as barometer of social welfare

Social factors include poor quality of life, poor housing, overcrowding, population explosion, undernutrition, lack of education, large families, & lack of awareness of causes of illness

All these factors are interrelated & contribute to the occurrence & spread of TB

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MODE OF TRANSMISSIONTransmitted mainly by

droplet infection and droplet nuclei – by sputum-positive patients with pulmonary TB

Coughing generates the largest number of droplets of all sizes

Frequency & vigour of cough & the ventilation of the enviroment influence transmission of infection

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Incubation periodTime from receipt of infection to the

development of a positive tuberculin test ranges from 3 to 6 weeks

Development of disease depends upon the closeness of contact, extent of disease & sputum positivity of the source

Incubation period may be weeks, months or years

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TYPES OF TB Pulmonary,

In active cases – most commonly involves the lungs (90% cases)

Symptoms – Chest pain & a prolonged cough producing sputum

About 25% of people - asymptomatic Extra pulmonary,

In 15–20% of active cases, the infection spreads outside the lungs, causing other kinds of TB

More commonly in immunosuppressed persons and young children

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CONT.

Extrapulmonary tuberculosis,

Common sites areMeninges Lymph nodesBones & joints Intestine Genitourinary tract

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CONT.

A potentially more serious, widespread form of TB - "disseminated" TB - commonly known as Miliary Tuberculosis.

Miliary TB -10% of extrapulmonary cases

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PATHOGENESIS

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CLINICAL FEATURES

•Coughing that lasts two or more weeks•Coughing up blood•Chest pain, or pain with breathing or coughing•Unexplained weight loss•Fatigue•Fever•Night sweats•Chills•Loss of appetite

Signs and

symptoms of active

Tuberculosis

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CHILDHOOD TUBERCULOSIS WHO estimates(2013) – Upto 80,000 children die from

TB each year & children account for over half a million new cases annually.

Estimated deaths only include – HIV-negative children

Actual burden of TB in children is likely higher, especially given the challenge in diagnosing childhood TB

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CONT.Children with TB,

Poor familiesLack of knowledge about the diseaseLive in communities with limited access to health

services

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HIV & TBPeople living with HIV – 26 to 31 times more likely

to develop TB than persons without HIV

TB - Most common presenting illness Among people living with HIVAmong those taking antiretroviral treatmentIt is the major cause of HIV-related death.

Sub-Saharan Africa – dual epidemic, accounting for approximately 78% of the estimated burden in 2013

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COLLABORATIVE TB/HIV ACTIVITIES

To address HIV-related TB, WHO recommends a 12 point package of collaborative TB/HIV activities.

Objectives,Reducing burden of TB among people living with HIVReducing burden of HIV among TB patients.

Implementation of these activities from 2005 to 2011 – Saved 1.3 million lives

Universal access to these life-saving measures must be achieved & eliminate HIV-associated TB deaths

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MDR-TB Multi-drug-resistant tuberculosis (MDR-TB) is defined

as – tuberculosis that is resistant to at least isoniazid (INH) and rifampicin (RMP),the two most powerful first-line treatment anti-TB drugs

When the course of antibiotics is interrupted – levels of drug in the body are insufficient to kill 100% of bacteria

Spread from person to person as readily as drug-sensitive TB and in the same manner

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CONT.

Most commonly develops in the course of TB treatment,

Inappropriate treatmentMissing doses or Failing to complete their treatment

Multidrug-resistant strain can transmit TB if pathogens are alive & patient coughing

TB strains –often less fit & less transmissible & outbreaks occur more readily in people with weakened immune systems (HIV)

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PREVENTION OF DRUG RESISTANCE TB

Rapid diagnosis & treatment of TB:

• One of the greatest risk factors, especially in developing countries• If TB is identified & treated soon, drug resistance can be avoided.

Completion of treatment:

• Previous treatment of TB is an indicator of MDR TB. • Incomplete antibiotic treatment, or improper prescription of antibiotic regimen – resistance can develop. • Drugs that are of poor quality or less in quantity, especially in developing countries contribute to MDR TB

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Patients with HIV/AIDS should be identified & diagnosed as soon as possible. They lack the immunity to fight the TB infection & are at great risk of developing drug resistance.

Identify contacts who could have contracted TB: i.e. family members, people in close contact, etc.

Much research and funding is needed in the diagnosis, prevention and treatment of TB and MDR TB

PREVENTION OF DRUG RESISTANCE TB

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EXTENSIVELY DRUG RESISTANT

XDR-TB is defined as TB that has developed resistance to at least rifampicin and isoniazid , as well as to any member of the quinolone family and at least one of the following second-line anti-TB injectable drugs:

KanamycinCapreomycinAmikacin

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CONT. If TB bacteria are found in the sputum – diagnosis of TB can be made in a

day or two, but can’t distinguish bet. drug-susceptible & drug-resistant TB.

To evaluate drug susceptibility, bacteria need to be cultivated & tested in a suitable laboratory. Final diagnosis in this way for TB, & especially for XDR-TB, may take from 6 to 16 weeks

The original method used to test for MDR-TB & XDR-TB – Drug Susceptibility Testing (DST).

DST is capable of determining how well four primary ATT drugs inhibit the growth of Mycobacterium Tuberculosis

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PREVENTION & CONTROL OF TUBERCULOSIS

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Prevention & controlPrimary prevention- health education &

specific protection ◦Population strategy & high risk strategy

Secondary prevention- early diagnosis & specific treatment

Tertiary prevention- rehabilitation & disability limitation

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PREVENTION & CONTROL OF TB

Early diagnosis and treatment, particularly of sputum smear positive cases – cornerstone of tuberculosis control

The Revised National Tuberculosis Control Programme (RNTCP) has focused on achieving high cure rates

The protective efficacy of BCG has ranged between 0 to 80% in different studies

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BCG-VACCINEThe first human was vaccinated by the

intradermal technique in 1927BCG is the only widely used live bacterial

vaccine. It consists of living bacteria derived from an attenuated bovine strain of tubercle bacilli

The WHO has recommended the "Danish 1331" strain for the production of BCG vaccine

Since January 1967, the BCG Laboratory at Guindy, Chennai, has been using the "Danish 1331" strain for the production of BCG vaccine

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CONT..

There are two types of BCG vaccine - the liquid (fresh) vaccine and the freeze dried vaccine.

For vaccination. the usual strength is 0.1 mg 0.1 ml volume. The dose to newborn aged below 4 weeks is 0.05 ml.

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RNTCPNeed for a Revised Strategy India has had an on-going National TB Program, NTP

since 1962. Program reviews showed that only 30% of estimated tuberculosis patients were diagnosed & treated successfully.

Based on the findings & recommendations of the review in 1992, the GOI evolved a revised strategy and launched the Revised National TB Control Programme (RNTCP) in the country.

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COMPONENTS OF RNTCP

The directly observed treatment, short-course DOTS strategy along with the other ingredients of the Stop TB Partnership are implemented as a comprehensive package for TB control.

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FIVE PRINCIPAL COMPONENTS OF DOTS

Political and administrative commitment

Case detection by sputum smear microscopy

Uninterrupted supply of high-quality anti-TB drugs

Standardized treatment regimens with directly observed treatment for at least the first two months

Systematic monitoring and accountability

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MANTOUX TEST The Mantoux test OR Mendel-Mantoux test OR the Mantoux

screening test OR tuberculin sensitivity test OR Pirquet test OR PPD test for purified protein derivative-screening tool for TB

Tuberculin is a glycerol extract of the tubercle bacillus. PPD tuberculin -precipitate of species-nonspecific molecules obtained from filtrates of sterilized, concentrated cultures

A standard dose is 5 tuberculin units (TU - 0.1 ml) is injected intradermally (between the layers of dermis) and read 48 to 72 hours later

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CONT.

The reaction is read by measuring the diameter of induration (palpable raised, hardened area) across the forearm (perpendicular to the long axis) in millimeters

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CLASSIFICATION OF TUBERCULIN REACTIONThe person's medical risk factors determine at which increment (5 mm, 10 mm, or 15 mm) of induration the result is considered positive. A positive result indicates TB exposure.• An HIV-positive person• Persons with recent contacts with a TB patient• Persons with nodular or fibrotic changes on chest X-ray consistent with old healed TB• Patients with organ transplants, and other immunosuppressed patients

5 mm or more is positive in

• Injection drug users• Residents and employees of high-risk congregate settings (e.g., prisons, nursing homes, hospitals, homeless shelters, etc.)• Mycobacteriology lab personnel• Persons with clinical conditions that place them at high risk (e.g., diabetes, prolonged corticosteroid therapy, chronic malabsorption syndromes, etc.)• Children less than 4 years of age, or children and adolescents exposed to adults in high-risk categories

10 mm or more is positive in

• Persons with no known risk factors for TB

15 mm or more is positive in

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STOP TB STRATEGY

• DOTS expansion & enhancement • Addressing TB/HIV, MDR - TB &

other challenges• Contributing to health system

strengthening• Engaging all care providers • Empowering patients & communities• Enabling & promoting research

STOP TB STRATE

GY6 Major compone

nts

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SUMMARYDespite all these national programmes &

efforts from govt of India , TB still continues to be a major socio-economic burden of the country

Still there is need to create awareness among health care professionals, and the community

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