Practical TB Infection Control for Community-based TB Programs

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Practical TB Infection Controlfor
Community-based TB Programs

• Kevin Fennelly, MD, MPH
• Center for Emerging Re-emerging Pathogens
• Interim Director
• Division of Pulmonary Critical Care Medicine
• UMDNJ-New Jersey Medical School
• fennelkp_at_umdnj.edu
• 11 June 2008

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Objectives

• To help identify situations in which there is an
  increased risk of TB transmission
• people (patients) and places (settings)
• To recommend practical solutions
• for programs to help protect staff
• principles and provisions
• for staff
• knowledge is power and prevention !!

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Areas I will NOT cover

• Abundant evidence that HCWs are at increased risk
  for occupational TB infection (and disease)
• HCW anyone exposed to patients
• Risk assessment
• Would consider most environments in TB-endemic
  countries at high risk

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from Sol Permutt, 2004
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TB is transmitted by aerosols (NOT sputum)
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Particle size suspension in air

• Particle size deposition site
• 100 ?
• 20 ?
• 10 ? upper airway
• 1 - 5 ? alveolar deposition

• Time to fall the height of a room
• 10 sec
• 4 min
• 17 min
• Suspended indefinitely by room air currents

from Sol Permutt, 2004
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Estimates of Mtb Aerosol Production (quanta per
hour)

• TB ward pt on Rx
• Cavitary TB no Rx
• Laryngeal TB
• Bronchoscopy/ETT
• Autopsy

• 1.25
• 13
• 60
• 250
• 1000

- Fennelly KP. Int J Tuberc Lung Dis
1998 2 S103
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Who is Infectious?

• Sputum smear gt smear
• AFB 3-4 gt AFB 1-2
• Cavitary gt non-cavitary
• Close gt casual contact
• Prolonged gt brief contact
• Men gt women
• Young gt old
• Borgdorff MW et al. Am J Epidemiol 2001 154934
• HIV HIV
• Cruciani M et al. Clin Infect Dis 2001 331922
• MDR vs. DS ?

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Where are Patients Most Infectious?

• Congregate settings
• Hospitals
• Correctional facilities
• Bars
• Choirs
• Airplanes, ships
• Indoors gtgt outdoors
• Increased with crowding proximity
• But no data on UV-A or UV-B effects

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When are Patients Most Infectious?

• Coughing gt Singing gt Talking
• Loudon RG et al. Am Rev Respir Dis 1969100165
• Aerosol producing procedures intubation,
  bronchoscopy, sputum induction
• Sepkowitz KA. Clin Infect Dis 199623954
• Not on treatment
• Unrecognized/undiagnosed
• Drug-resistant on standard therapy

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Cough Frequency Infectiousness
Loudon RG Am Rev Respir Dis 1969, 99 109.
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What is Infectious?

• Dogma 1-5 micron infectious droplet nuclei
  (Wells, 1955)
• Risk associated with prolonged exposures
• Reality Wells estimated particle size
  distribution based on experimental nebulization
  of bacillary suspensions in lab
• No data from patient-generated aerosols
• Wells calculated droplets less than 25 microns
  dessicated to size of infectious droplet nuclei
  in less than one second

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Cough Aerosol Sampling System
- Fennelly KP et al. Am J Resp Crit Care Med
2004 169 604-9
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Six-stage Andersen cascade impactor
Andersen AA. J Bacteriol 195876471.
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Cough-generated aerosols of M.tb National Jewish
Medical Research Center
- Fennelly KP et al. Am J Resp Crit Care Med
2004 169 604-9
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Cough Aerosol Sampling System
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Frequency Distribution of Cough-generated
Aerosols of M. tuberculosis and Relation to
Sputum Smear Status
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Cough-generated Aerosols of M.
tuberculosisNormalized Particle Sizes
Lower limit of size range(µ) 7.0 4.7 3.3
2.1 1.1 0.65 Deposition
Upper airway - bronchi -- alveoli
Abstract, ATS International Conference, 2004.
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Cough Aerosol ProductionMultivariate Analysis

• Best model in logistic regression
• Bacillary concentration BACTEC lt 4 days to
  positive (OR11.35, p0.02) and
• strong cough (OR5.41, p0.04)
• Cough strength is associated with performance
  score (physical health) (Chi-square, p0.004).
• Cough strength tends to be associated with CD4
  counts (less advanced HIV infection)
  (Chi-square, p0.07).
• CD4 counts and performance scores drop out of
  multivariate models probably due to correlation
  with cough strength.
• These data suggest that healthier patients are
  more likely to be infectious than very ill
  patients.

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Aerosol CFUs Predict Infectivity in Mice
Abstract, Keystone Symposium on Tuberculosis,
2005.
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Wells-Riley Mathematical Model of Airborne
Infection
Assumptions Homogenous distribution of
infectious aerosol over 10 hours uniform
susceptibility.
- Fennelly KP Nardell EA. Infect Control Hosp
Epidemiol 1998 19754
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Summary PrinciplesTB-IC for Community Programs

• The most infectious TB patients are those who are
  not on appropriate therapy
• Undiagnosed, i.e., unrecognized
• Drug resistant
• TB is transmitted by aerosols
• Coughing and bacillary load important
• Healthier patients may be more infectious
• Poorly ventilated indoor environments the highest
  risk

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Summary PracticesTB-IC for Community Programs

• Best administrative control
• Suspect and separate until diagnosed
• Surveillance of HCWs with TST (and/or IGRAs) and
  rapid treatment of LTBI if conversions occur
• Best environmental control Ventilation
• Do as much as possible outdoors
• Use directional airflow when possible
• Natural breeze or fans HCW upwind patient
  downwind
• Personal respiratory protection
• N95 respirators when indoors or very close
  (procedures)
• Surgical masks on patients to control source

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