Epidemiology of TB and its control Dr. V. K. Chadha Sr. Epidemiologist National TB Institute Bangalore

1. Epidemiology of TBand its controlDr. V. K. ChadhaSr. EpidemiologistNational TB InstituteBangalore

3. Why do we need to study Epidemiology of TB?

4. Aims of Epidemiology ? To describe natural history of disease Describe Distribution and relative importance Measure frequency To define risk groups To evaluate interventions To describe trends To predict future trends and changes in disease presentation.

5. What is Epidemiology ? Epi - among ; Demos - People ; Logos - Study DEFINITION Epidemiology is the study of the - Frequency Distribution - time, place & person Determinants - physical, biological, social, behavioural & cultural of health problems & health related events and application of this study to control health problems.

7. Risk of exposure ? Incidence / prevalence of infectious TB in the community Duration of infectiousness opportunities for case - contact interactions -Urban/Rural -No. of individuals in the house holds

8. Risk of Infection ? No. of infectious droplets produced Volume of shared air space Length of exposure Ventilation Climatic conditions

10. Household transmission of TB- important epidemiological factor Case control study in Malawi

14. What is the most important risk factor for TB?

16. Risk factors for disease given that infection has occurred ?

17. Incidence of TB in South Africa per 1000 population

18. Other High Risk Groups Populations in war / civil unrest Refugees and migrants Slum dwellers Homeless people/Foot path dwellers Smoking Prisoners

19. TB in prisons Studies in Thailand TB incidence 90 times higher in prisons High HIV sero-positivity in TB cases High levels of drug resistance RFLP studies signify role of recent transmission

21. Determinants of death? Severity of illness Smear positivity delay in diagnosis quality of treatment drug susceptibility pattern

22. Epidemiological indicators of TB and their estimation

23. Enumerate epidemiological indicators of TB you know of?

24. Epidemiological indicators of tuberculosis ? Prevalence of infection Incidence (average annual risk) of infection (ARI) Prevalence of disease Incidence of disease Tuberculosis mortality rates

25. How to estimate prevalence of infection?

26. Estimating prevalence of infection Study population-sampling Registration of eligible age group - house-to-house / school based. Informed consent. Examination for BCG scar. Tuberculin testing with 1TU/2TU PPD RT23 with tween 80. Reading of reaction sizes appx. 72 hours later.

27. What is the rationale behind tuberculin surveys in children ? Extent or recent transmission Study trends in TB epidemiology (Ultimate aim of control programme is to replace older more infected cohorts with younger less infected cohorts)

28. Analysis of tuberculin survey

31. Estimation of incidence of infection?

32. Dual skin testing at two different periods -Conversion -Boosting Compute average annual risk of infection (ARTI) = 1-(1-P)1/A  

33. A RT I Key epidemiological indicator in developing countries. It is the probability of acquiring new tuberculosis infection or re-infection over the course of one year.

34. A R I expresses the overall impact of various factors influencing the transmission of tubercle bacilli ! - Load of infectious cases - Efficiency of case finding - Efficiency of treatment programme

35. ARI identifies the regions of high transmission It provides an indirect estimate of size of sources of infection Any change in disease burden and programme implementation is first reflected in the change in ARI It holds the key to the study of epidemiological trends which are more important than exact estimates of disease prevalence

36. How to estimate prevalence of disease?

37. DISEASE SURVEY METHODOLOGY  Sampling of representative population House to house registration Screening: - MMR X-ray of all above five years of age - Symptomatic screening X-ray pictures read by two independent readers and by an umpire reader Sputum specimens (2/3) collected from persons with abnormal X-ray shadows & / or chest symptomatics Sputum examination by direct microscopy (and culture).

38. How to estimate disease incidence?

39. Relationship between ARTI and incidence of disease

40. Styblo derived the following relationship from data of pre- chemotherapy Every one percent of ARTI corresponds to 50 new smear positive cases per 100,000 population per year

41. Relationship between ARI & Incidence of smear positive cases of Pulmonary Tuberculosis(Indian studies)

42. Relation between ARI and Incidence ! Situation : Disease incidence remains same but the risk of infection declines Q 1. When is this situation likely? Q 2. What is the impact on equation (relationship) ?

43. What happens to the equation in high HIV settings?

44. The equation is dependent more on number of infections generated per case and not merely on incidence

45. Disease mortality rates ! Community based prospective studies Death certification

52. Does higher ARTI in urban areas indicate higher incidence of smear positive cases

54. Other Epidemiological indicators of Tuberculosis Ratio of prevalence and incidence Age distribution of cases Case fatality rates Force of MDR cases TBM notification rates Disability adjusted life years (DALY)

55. Epidemiological trends of TB

59. TB trends in EuropeMedian age in Finland

60. TB trends in EuropeNetherlands

61. Global drug resistance surveillance

64. Trends in ARI-Chingleput At intake in 1969 : 1.8% After 4 years in 1973 : 1.8% After 10 years : 1.9% After 15 years : 1.7%

65. How does HIV pandemic influence TB epidemic

66. Higher rate of progression from latent infection to disease (5-10% per year compared to 10% per year among HIV negative) Previously HIV infected persons when exposed to TB rapidly develop the disease. Excess cases due to the above lead to increased transmission of infection Higher case fatality due to HIV infection

67. Evidence of association between HIV and TB Increase in TB in areas worst affected by HIV Higher increase in age group affected by HIV. 50 to 70% AIDS cases develop TB in SEAR. HIV positivity higher among TB cases than general population. -Northern Thailand: HIV positivity in TB cases : 40% : Malawi : 75%

77. In your opinion, what should be the practical methods of monitoring epidemiological trends in any given community

78. Global picture 3rd largest cause of death (2.8%) and loss of DALYs in 15-59 year age group Incidence all cases - 8.8 million (2002)-141/100000 in 22 HBCs - 7.0 million (80%) Smear + - 3.9 (63/100000) million Case notifications of smear positive cases increasing @ 4% per year- 5% in eastern Europe and 7% in high HIV African countries.

80. Epidemiological situation of TB in South East Asian countries

81. Format for Country presentations

82. TB in South-East Asia

83. HIV-TB in SEAR Second largest number of HIV positives after SSA SSA:60% SEAR:30% 6 million HIV positives in SEAR India :4 mill Thailand :1 mill Myanmar :0.5 mill Low sero-positivity in Bangladesh, Maldives, Bhutan, Indonesia and Sri lanka Nepal : Low in antenatal women, high among IDUs.

84. TB situation in India

87. INCIDENCE OF PULMONARY TUBERCULOSIS IN INDIA

88. HIV Sero-prevalence among TB Cases

89. Multi Drug Resistance in new TB cases

91. ARI in other countries

95. Progress of DOTS in high burdened countries

96. What is meant by control ? To move from high to low endemicity or elimination

97. Objectives of TB control programmes Decrease transmission of infection by:- - Rapidly identifying cases - Adequate treatment Decrease deaths due to TB. Cure of maximum number of cases. To prevent relapse. To prevent emergence of drug resistance. To reduce TB in children by preventive treatment. IEC - Purpose ?

99. How does DOTS strategy help control TB?

100. DOTS Decreases deaths Decreases duration of infectiousness Increased case detection plus high cure rate decreases transmission of infection that will ultimately lead to decline in incidence. Prevents emergence of MDR

101. A good programme like DOTS reduces disease burden Case fatility rate reduced to <5% compared to 60%-70% in a few years among untreated cases. Cure of every case under DOTS with about 4 months diagnostic delay prevents 0.7 new smear positive cases.(further prevention possible by reducing diagnostic delay) Preventive treatment to each child prevents 0.03 new case and 0.007 deaths.

102. How does a poor programme worsen the TB situation

103. Poor programme with low cure rate (<50%) and low detection rate worsen TB situation by decreasing case fatility rates leading to increased prevalence and transmission of infection.

104. HIV prevention and control is of major importance towards TB control

105. Priority to smear positive cases To reduce transmission of infection. A good DOTS programme would reduce transmission of infections by about 73% Cost per DALY highest for treating smear positive cases.

106. The Cuba example

108. Very low levels of MDR in Cuba Cuba is a low HIV country

110. Increased case detection will decrease transmission rapidly provided cure rates are high. It has been estimated that achievement of 70% case detection and 85% cure rate by 2010 will result in greatest benefits in cases and deaths averted in regions with highest burden - South East Asia, Africa and Western Pacific. Longer the time taken to reach targets, incidence will decrease more slowly. The proportion of deaths averted by DOTS would be greater than the proportion of cases Non curative treatment can prevent death without eliminating infectiousness. Programme will treat non-infectious cases also

111. Control TB since every breadth counts (World TB day 2004 theme) Business as usual will not eliminate TB It is time for business unusual