TB Infection Control: Principles, Pitfalls, and Priorities

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TB Infection ControlPrinciples, Pitfalls, and
Priorities

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

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Objectives

• To review basic principles underlying TB
  transmission and TB Infection Control policies.
• To review the recent history of TB Infection
  Control.
• 3. To discuss personal observations and offer
  practical solutions to common problems in TB
  Infection Control.

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Is TB an Occupational Disease of HCWs?
Low- middle-income countries High-income countries
LTBI (prevalence) 63 (33-79) 24 (4-46)
TB disease (annual incidence) 5.8 (0-11) 1.1 (0.2-12)
TB mortality (inpt) (PMR) (outpt) ?? 1.18 (1.04-1.35) 3.04 (1.62-5.19)
- Menzies D et al. IJTLD 2007 11593
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HCW Deaths due to Nosocomial Transmission of
DR-TB

• MDR outbreaks U.S. 1980s-1990s
• 9 HCWs died
• All immunocompromised, 8 with HIV
• Sepkowitz KA, EID 2005
• XDR-TB outbreak, So Africa, 2006
• 52/53 died of unrecognized XDR-TB
• 44/44 tested were HIV
• Median survival from sputa collection16 days
• 2 HCWs died 4 others sought care elsewhere
• Gandhi N, Lancet 2006

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Personal Respiratory Protection Against M.
tuberculosis Contentious Controversy
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from Sol Permutt, 2004
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Wells-Riley Equation Mathematical model of
airborne infection
PrinfectionC/S1-e(-Iqpt/Q) Where C S
infected S susceptibles exposed I infectors
( active pulm TB cases) q infectious units
produced/hr/Infector p pulm ventilation
rate/hr/S t hours of exposure Q room
ventilation rate with fresh air
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Control Measures are Synergistic Complementary
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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Wells-Riley Mathematical Model of Airborne
Infection
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TB is Spread by Aerosols, NOT sputum
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Particle size suspension in air( NOT size of
bacilli)

• 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

- Courtesy of Sol Permutt, 2004
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Six-stage Andersen cascade impactor
Andersen AA. J Bacteriol 195876471.
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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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Cough-generated aerosols of MtbInitial Report
from Denver, CO4 of 16 (25) of SS subjects
- Fennelly KP et al. Am J Resp Crit Care Med
2004 169 604-9
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Variability of Infectiousness in TBEpidemiology

• Rotterdam, 1967-69 Only 28 of smear positive
  patients transmitted infections.
• Van Geuns et al. Bull Int Union Tuberc 1975
  50107
• Case control study 796 U.S. TB cases
• Index cases tended to infect most (or all) or few
  (or none) of their contacts
• Snider DE et al. Am Rev Respir Dis 1985 132125
• Ability to publish outbreaks suggests that they
  are episodic.

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Variability of Infectiousness in TB
Experimental

• All infections attributed to 8 of 61 (13)
  patients. 50 of infections due to one
  patient with TB laryngitis.
• Riley RL et al. Am Rev Respir Dis 1962 85511.
• 3 (4) of 77 patients produced gt 73 of the
  infections in the guinea pigs.
• Sultan L. Am Rev Respir Dis 1967 95435.
• Recent replication of this model in Peru
• 118 hospital admissions of 97 HIV-TB coinfected
  patients
• 8.5 caused 98 of secondary GP infections
• 90 due to inadequately treated MDR-TB
• Escombe AR et al. PLoS Medicine 2008 5e188

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Occupational TB in Sub-Saharan Africa

• Malawi
• 25 mortality
• Harries AD, Tran R Soc Trop Med Hyg 1999 93 32
• Ethiopia
• South Africa
• Nigeria
• 32 of 2,173 HCWs
• 15 (47) as HIV-TB
• Salami AK, Nigerian J Clin Prac 2008 11 32

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What is the magnitude and variability of
infectious aerosols of M. tuberculosis?(Can we
better identify the most infectious?)
Hypothesis 1 Cough-generated aerosols of Mtb
can be measured in resource-limited
settings. Hypothesis 2 Cough-generated aerosols
will be detected in approximately 25-30 of
patients with PTB.
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Cough Aerosol Sampling Systemv.2
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Frequency Distribution of Cough-generated
Aerosols of M. tuberculosis and Relation to
Sputum Smear Status31/112 (28) SS subjects
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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 Anatomical deposition
Upper airway -- bronchi -- alveoli
Abstract, ATS International Conference, 2004.
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Pitfalls in Administrative Controls

• TB Mortality not prioritized or under
  surveillance (i.e., no data collection)
• HIV screening of HCWs not prioritized
• major risk factor for TB disease death
• HAART now feasible in much of world
• HIV screening advocated for admt patients in US
• TB laboratory personnel often not involved in TB
  infection control efforts
• Botswana 1st AFB smear STAT
• Decisions re infectiousness falls onto
  clinicians with variable expertise

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Pitfalls in Environmental Controls

• Little or no engineering expertise and support
  for hospitals HCFs
• No systems of communication / interaction
• Different cultures and mind-sets
• TB nurses or administrators subject to sales
  pitches from commercial vendors
• UVGI lamps in SANTA facilities
• Mobile air filters in Newark, NJ
• Lack of appreciation of natural ventilationand
  its limitations!
• Low rate of nosocomial infection in Uganda
  project
• High rate in Tugela Ferry

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Pitfalls in Personal Respiratory Protection

• Too much attention paid to masks at expense of
  administrative and environmental measures
• Rizdon R et al Renal unit with poor ventilation
• Inappropriate use on patients
• Focus on fit-testing and regulation rather than
  on follow up on use in field
• Lack of appreciation that not all respirators
  provide the same level of protection
• Need for more protection in high-risk
  aerosol-inducing procedures, e.g., bronchoscopies

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TB-IC Practices 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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Summary TB-IC

• Administrative controls most important component
  of TB-IC
• Suspect and separate!
• Prioritize screening HIV in HCWs
• Prioritize good ventilation in all areas
• Back-up in areas with poor ventilation
• Fans, mechanical ventilation, UVGI
• Prioritize personal respiratory protection for
  high risk settings, esp where admin and environ
  controls limited