Presentation on theme: "Practical TB Infection Control for Community-based TB Programs Kevin Fennelly, MD, MPH Center for Emerging & Re-emerging Pathogens Interim Director Division."— Presentation transcript:
Practical TB Infection Control for 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 11 June 2008
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 !!
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
from Sol Permutt, 2004
TB is transmitted by aerosols (NOT sputum)
*NOT organism size 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
Estimates of Mtb Aerosol Production (quanta per hour) TB ward: pt on Rx Cavitary TB: no Rx Laryngeal TB Bronchoscopy/ETT Autopsy Fennelly KP. Int J Tuberc Lung Dis 1998; 2: S103
Who is Infectious? Sputum smear + > smear – –AFB 3-4+ > AFB 1-2+ Cavitary > non-cavitary Close > casual contact Prolonged > brief contact Men > women Young > old Borgdorff MW et al. Am J Epidemiol 2001; 154:934 HIV+ = HIV – Cruciani M et al. Clin Infect Dis 2001; 33:1922 MDR vs. DS: ?
Where are Patients Most Infectious? Congregate settings –Hospitals –Correctional facilities –Bars –Choirs –Airplanes, ships Indoors >> outdoors –Increased with crowding & proximity –But no data on UV-A or UV-B effects
When are Patients Most Infectious? Coughing > Singing > Talking Loudon RG et al. Am Rev Respir Dis 1969;100:165 Aerosol producing procedures: intubation, bronchoscopy, sputum induction Sepkowitz KA. Clin Infect Dis 1996;23:954 Not on treatment –Unrecognized/undiagnosed –Drug-resistant on standard therapy
Loudon RG Am Rev Respir Dis 1969, 99: 109. Cough Frequency & Infectiousness
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
Cough Aerosol Sampling System - Fennelly KP et al. Am J Resp Crit Care Med 2004; 169; 604-9
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
Cough Aerosol Sampling System
Frequency Distribution of Cough-generated Aerosols of M. tuberculosis and Relation to Sputum Smear Status
Cough-generated Aerosols of M. tuberculosis: Normalized Particle Sizes Lower limit of size range(µ) Deposition Upper airway - bronchi -- alveoli Abstract, ATS International Conference, 2004.
Cough Aerosol Production: Multivariate Analysis Best model in logistic regression –Bacillary concentration: BACTEC™ < 4 days to positive (OR=11.35, p=0.02) and –strong cough (OR=5.41, p=0.04) Cough strength is associated with performance score (physical health) (Chi-square, p=0.004). –Cough strength tends to be associated with CD4 counts (less advanced HIV infection) (Chi-square, p=0.07). –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.
Aerosol CFUs Predict Infectivity in Mice Abstract, Keystone Symposium on Tuberculosis, 2005.
Assumptions: Homogenous distribution of infectious aerosol over 10 hours; uniform susceptibility. - Fennelly KP & Nardell EA. Infect Control Hosp Epidemiol 1998; 19;754 Wells-Riley Mathematical Model of Airborne Infection
Summary: Principles TB-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
Summary: Practices TB-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