Synopsis• Introduction• History of TB- Timeline• Epidemiological indices• Geographical distribution in Estimates of TB- World, SEAR & India• Time Trends in estimates of TB• Person distribution of TB• Agent, Host & Social factors• Natural history of disease
Learning objectives By the end of this session the students will be able to1. Describe the time, place & person distribution of Tuberculosis2. Specify the epidemiological determinants of TB3. Describe how TB is spread from person to person4. Describe the Natural history of TB
Introduction • Infectious disease caused by Mycobacterium tuberculosis • Can also affect intestines, meninges, bones & joints, lymph glands, skin and other tissues • Also affects animals like cattle- Bovine tuberculosis TB is curable & preventable
History of TB- Timeline 400 B.C. 1500- Giralamo 1860’s- Louis3700 B.C TB in Hippocrates- Fracastoro (Italy)- Pasteur- airborneancient Egypt excellent clinical TB contagious transmission description1944- 1930’s- WilliamStreptomycin Wells- conclusive 1882- Robert Koch- 1921- BCG evidence of Isolation of TB1952- Isoniazid introduced airborne bacillus1960- 2 years tt. transmission 2011/12- atleast 1 1993- Global 2006- I case of1970’s – MDR TB case of XDR-TB in health emergency XDR-TB 69 countries
Tuberculosis-one of the biggest public health challenges facing world today• One of the oldest diseases known• M. tuberculosis - one of the first bacterial pathogens identified• Etiopathogenesis clearly understood• Vaccine available for close to a century• Effective treatment available for > 60 years 2nd only to HIV/AIDS as an infectious cause of death worldwide Declared Global Public Health Emergency in 1993
Epidemiological indices in TB1. Prevalence of Infection (Tuberculin index)2. Incidence of Infection (Annual Infection rate)3. Prevalence of Disease (Case rate)4. Incidence of New cases5. Prevalence of “Suspect” cases6. Case detection rate7. Prevalence of drug-resistant cases8. Mortality rate
Estimated TB Incidence rates, 20108.8 million incident cases12 million prevalent cases Source: Global Tuberculosis Control 2011,1.4 million deaths WHO
Global estimates, 2010Estimates of Prevalence Estimates of Mortality• 12 million prevalent cases in • 1.4 million deaths 2010 worldwide (20 deaths per 1• 178 cases per 100000 lakh population) population • 1.1 million deaths among HIV negative • 0.35 million deaths among HIV positive Source: Global Tuberculosis Control 2011, WHO
TB: A Global Health Crisis• Nearly 1% of the world’s population newly infected each year• Overall 1/3rd of world’s population, nearly 2 billion people are infected with TB• 200 million people worldwide, or 10% of those infected will develop active TB & be able to infect others (10-15 persons per year) for 3 decades• TB kills 8000 people a day- i.e. 2-3 million people each year www.who.int/tbfacts/en
7 billion1/3rd of world population 2 billion infected with TB10% of the infectedpeople 200 million will develop active TB
5 million prevalent cases3.5 million incident cases5 out of 22 high burden countries
Estimates of TB burden in India, 2010 (provisional)accounting for an estimated one quarter (26%) of all TB cases worldwideEstimates of Number (millions) Rateburden (per 100,000 pop)Mortality (excluding HIV) 0.32 (0.21 – 0.47) 26 (17 – 39)Prevalence (including HIV) 3.1( 2 – 4.6) 256 (161 – 373)Incidence (including HIV) 2.6 (2.0 – 2.5) 185 (167 – 205)Incidence (HIV positive) 0.110 (0.075 – 0.160) 9.2 (6.1 – 13) Source: Global Tuberculosis Control 2011, WHO
Magnitude of TB in India• India ranks first with the largest number of incident cases (2-2.5 million)• India has about 2.2 million new cases every year including about 1 million sputum positive cases.• Estimated 3.5 million cases are sputum positive.• 0.5 million people in India die from TB every year.• MDR-TB Prevalence among new cases: 2.3%
Global trends in estimated rates of TB Incidence, Prevalence & Mortality Incidence Prevalence Mortality HIV Positive Source: Global Tuberculosis Control 2011
Global trends- contd..• Absolute number of incident TB cases has been on ↓ since 2006• 128 incident cases per 100000 population in 2010• 59% in Asia (26% in Africa)• 22 High burden countries accounted for 81% of cases• Incidence rate falling by 1.3% per year since 2002• TB mortality decreasing- close to STOP TB partnership goal• TB prevalence decreasing, but…
Trends in SEAR, 1990-2010 Source: Global Tuberculosis Control 2011
Estimated prevalence rate in member states of SEAR Source: Global Tuberculosis Control 2011, WHO
Estimated mortality rates in member states of SEAR Source: Global Tuberculosis Control 2011, WHO
TB Trends in India Source: Global Tuberculosis Control 2011, WHO
Human and Economic Impact• TB kills more adults than all other infectious diseases combined.• More than one-quarter of all avoidable adult deaths are caused by TB.• TB strikes people in their most productive years, i.e. between the ages of 15 to 44.• Leading killer of people infected with HIV worldwide.
Age & sex distribution of all notified new smear positive cases in WHO-SEAR in 2010
TB & Women• TB is the single biggest killer of young women.• 3.2 million incident cases among women in 2010 (36%)• 0.32 million deaths from TB among women in 2010• Over one million women may needlessly die from TB this year. They are breadwinners, mothers, daughters and wives.
TB & Children• In 2010, 0.5 million children (0-14 years) infected with TB; 64000 child deaths due to TB• Over 100,000 children may needlessly die from TB this year.• Hundreds of thousands of children will become TB orphans this year.
TB & HIV• 1 in 3 HIV infected people worldwide co-infected with TB• People who are HIV- positive & infected with TB are 30 times more likely to develop active TB• Among 1.4 million TB deaths in 2010, 0.35 million deaths were in HIV positive.
AGENT FACTORS- Agent• My. tuberculosis• Human strain responsible → majority of the cases ROBERT KOCH (Germany, 1882)
Source of InfectionHuman source: human Bovine source: infectedcase whose sputum is milkpositive for the bacilli
Infective material & Communicability• Infective material is the sputum of TB patients• Infective as long as the persons are untreated• Effective chemotherapy reduces infectivity by 90% in 48 hours
Host factors• Age: all ages; sharp ↑ in Risk groups infection rates from • People who are childhood to adolescence malnourished• Sex: Males > Females • People who live in close• Heredity: not hereditary; quarters inherited susceptibility is • Healthcare workers an important risk factor • Long-term hospital• Nutrition patients• Immunity: acquired • Prison workers & inmates (natural infection/ BCG • People with weakened vaccination) immune systems
References• Park’s Textbook of Preventive and Social Medicine• Tuberculosis in South-East Asian Region, 2012, WHO• Global Tuberculosis Control, WHO Report 2011• http://www.who.int/tbfacts/• http://www.cdc.gov/tb/publications/pamphle ts/TB_disease_EN_rev.pdf