EPIDEMIOLOGY

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EPIDEMIOLOGY Powered By Docstoc
					INTERVENTIONS

           Jaap Veen,      MD,PhD

           Turkish Thoracic Society
                   Antalya
                  April 2005
TB control
               control
                         surveillance



             interventions


     agent     individual     community



                             epidemiology
Tuberculosis: infection and disease model


                No infection


   Contact                      No disease (90%)
      with
   infectious
      case
                                              No death
                Infection


                               Disease

                                              Death (50%)


          INTERVENTIONS
                          Transmission
                                                   Chemotherapy




                                         Doctor's delay


      Prophylactic         Preventive    Patient's delay
       treatment            therapy


                                           Infectious
                                          tuberculosis
                 Subclinical
Exposure                                                          Death
                  infection
                                         Non-infectious
                                          tuberculosis




                BCG
                                         Source: HL Rieder
Chain of Transmission



                    Index case



interventions                     interventions




                        contact
Definitions

 Strategy           a coherent set of
                     interventions
                    the use of tools to
 Interventions
                     reduce the risk of
                     disease
                    technical, economical,
 Tools
                     clinical and social
                     instruments to
                     produce measurable
                     result.
How to choose

 Tools              What is technically the
                     best tool (specificity,
                     sensitivity, rapidity,
                     adverse effects, impact,
                     etc)
                    What are the best tools
 Interventions
                     given the epidemiological
                     and financial situation
 Strategy           What is the most effective
                     (impact, cost) set of
                     interventions to achieve
                     the desired outcome
 Chain of Transmission:

 Interventions

                     Index case     Early
                                    Diagnosis
  BCG
  vaccination                       Adequate
                                    Treatment
Preventive
Chemotherapy                        Infection Control



                          contact
Early strategy

 Hippocrates


    • movement if possible
    • no sex
    • wash with warm water
    • 45 days raw milk
    • red wine OK, but if fever only white wine
Interventions:

Case detection
Interventions

1. Early case detection


    passive case detection    (symptomatics)
    active population based
     screening                 (risk groups)*



*   ONLY IF SYMPTOMATICS CAN BE CURED
Diagnosis:
what is the best tool
chest Xray vs AFB microscopy
Case detection:
What is the best intervention
active vs passive case detection




    20%                            80%

Mass          Symptoms and signs
Miniature
Radiography
Patient Delay

Increase public awareness

Several strategies:

Public Awareness Campaigns (PAC)
Brochures, leaflets
Multimedia approach
INTERVENTIONS

2. Treatment

Directed at agent
     drugs
     surgery

Directed at host
     palliative
     immunotherapy
     nutrition
INTERVENTIONS

2. Treatment

Early start of adequate treatment *
Decrease doctor’s delay**

* combination of drugs
  sufficient duration
  direct observation of rifampicin intake

** training
Treatment


  Palliative Treatment


  1st sanatorium in Germany:
  Brehmer (1857)
Treatment


  Sanatorium
     • good hygiene
     • bed rest and dosed movement
     • no sex
     • good climate
     • good diet
      decline of epidemic in the Netherlands by 6% per
      year (1910-1940)



mortality




risk of
infection




              1910       1940
      decline of epidemic in the Netherlands by 12% per
      year (1950-2000)




mortality




risk of
infection


morbidity



                          1950          2000
Treatment


  Steep decrease of mortality, morbidity and risk
  of infection:
     • introduction of effective drugs
     • eradication of bovine TB*


     * had its own strategy and set of
     interventions
Infection Control
Infection Control

1. Interventions directed at the source if infection
   [producer]
      1. Reduction of cough
      2. Cough hygiene
      3. Masks
2. Interventions directed at the air [transport medium]
      1. Engineering
           1. Ventilation
           2. Filtration
           3. UV irradiation
3. Interventions directed at the contact [consumer]
      1.   personal protection (masks, respirators)
Cough Hygiene
Disinfection

In prisons different interventions are used
Florence Nightingale 1820-1910


                 Nurse

                 In 1854 sent to
                   Turkey to take care
                   of the wounded
                   British soldiers in
                   the Crimean war.
Appalling conditions-many soldiers died in
hospital
Implementation of hygienic measures
Infection Control

Personal Protection
INTERVENTIONS
Latent TB Infections


   Chemo prophylaxis
       newborn contacts,
       HIV infected


   Preventive chemotherapy
       Contacts
       TB infected with risk factors for disease


   Vaccination
INTERVENTIONS
Latent TB Infections


   Preventive chemotherapy
      Contact tracing *
      Choice of regimen (MDRTB !)




*   only if good system is in place
    following the ‘Stone-in-the-Pond Principle
                    Effect of Various Durations of Preventive Therapy
                    on Risk of Tuberculosis in Bethel Isoniazid Studies
                5


                4
Cases per 100




                3


                2


                1


                0
                    0     3      6       9      12       15      18      21

                                     Months of treatment
                                Comstock GW. Int J Tuberc Lung Dis 1999;3:847-50
INTERVENTIONS
Latent TB Infections

    Vaccination                                     is it effective?
                 Protection from BCG Vaccination - Prospective Studies
                                  Protection all Ages

                    Haiti                                          All forms

          N. Am. Indians                                           All forms

            Madanapelle                                            All forms

      Muscogee / Russell                                           All forms

              Muscogee                                             All forms, 5-28 yr,
                                                                   10-yr follow-up
              Chingleput                                           Pulmonary,
                                                                   Culture confirmed
                  Illinois                                         Mental institutions

                                                                   All forms, 5-28 yr,
              Muscogee
                                                                   20-yr follow-up

                             -400   -100   0 30 50     80    90       95
                                             Per cent protection
INTERVENTIONS
Latent TB Infections



Vaccination (BCG)

Is it effective?
     Newborns *
     High Risk Groups**
     MDRTB ?

*      only in high prevalence countries
**     only if no other means of protection
Interventions:
Ethical and Legal aspects


Examples
 Screening or isolation:

       Mandatory or Voluntary ?


   If voluntary:
       how much pressure may be exercised ?
TUBERCULOSIS
Strategies and Interventions over time


     First sanatorium
     Germany, 1857 First Dispensary,
                      Scotland, 1897             BCG vaccination




                                       Drugs, 1945-1962

              Koch, Mtb,                         MMR,1950-1980
              1882                                        Fox:Ambulatory treatment, 1968
                                                                Styblo model, 1978


                                                                                DOTS, 1991

                sanatoria                                                                    Outbreak Management,
                                                                                             Risk Group Management
                                                   screening



                                                 drug therapy

              Socio-economic improvement
Conclusion
Strategies use a set of interventions and what
  strategy is used depends on the epidemiological
  and financial situation and the desired impact

Interventions and their tools must be evaluated

      technically sound?        (evidence based)
      financially acceptable?   (advocacy)
      applied in practice?      (guidelines)
      achieving their goals?    (monitoring and
                                         evaluation)

				
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