Use of Network Analysis During a Tuberculosis Investigation Outbreak Investigation Section Surveillance and Epidemiology Branch Division of Tuberculosis Elimination National Center for HIV, STD, and TB Prevention Centers for Disease Control and Prevention Atlanta, GA April 21, 2003

TB Facts M. tuberculosis (M.Tb) airborne transmission Latent TB infection (LTBI) detected by tuberculin skin test (TST) 10 to 15 million LTBI 10% lifetime risk of progression to active TB

TB patientContact M. tuberculosis Transmission Infectiousness Exposure duration Room size Air exchange

Exposed contacts Latent TB infection Active TB disease Exposure…. Infection…. Disease T uberculin S kin T est

Concentric Circle Approach Household Leisure Work TB PATIENT Close Contacts Casual Contacts

Multiple Contact Investigations

The Concentric Circle Paradigm Assumes… Cases know their contacts Cases will reveal their contacts Casual contacts are less important Interconnections among contacts of contacts are unimportant

Each Contact Investigation Yields an Individual Transmission Unit TB patient “A” identifies 2 contacts Contact evaluated and found to be tuberculin skin test (TST) positive Contact evaluated and found to be tuberculin skin test (TST) negative

County’s Contact Data from Multiple TB Cases (A–D) Patient C has greater importance, but patient-specific TST-positive rates miss this importance A 50% TST+ B D C

Contacts Data Name, address, DOB Sex, ethnicity Places TST status Type of contact Strength of contact All the case variables No Shortage of Data

Outbreak

Objectives Identify case-patients and contacts Establish epidemiologic links among case-patients and contacts Make recommendations to control the outbreak

Methods Case-patients Contacts Data entered in ACCESS® database* InFlow™ 3.0 network analysis software* *Use of trade names and commercial sources is for identification only and does not imply endorsement by the U.S. Department of Health and Human Services

Index Case-Patient ED Visits Diagnosis of TB Restaurant Fever & Cough Jail

Contact Investigation: Index Case-Patient Identified Tested TST+ (  5 mm) RR (95%CI) Household (100%) 6.4 (2.9,14.3) Friend (52%) 3.4 (1.5,7.8) Jail (50%) 3.2 (1.4,7.3) Work/School (16%) Referent Hospital (11%) 0.7 (0.2,2.3) Total (42%)

Case-Patients by Date of Diagnosis (N=35) Nov 02 Culture confirmedClinical Case Index CDC invited

Contact Investigations N(%) Total Identified1,039 Evaluated 860 (83) TST  5mm 179 (21) Initiated treatment 135 (75) Female 474 (53) Age <5 45 ( 5) (20) (19)  (57) Black 390 (48)

Network Visualization

Network Key Nodes TB cases TST(+) contacts TST(-) contacts TST status unknown Links Close contact Casual contact

Are All TB Cases Associated?

Case-Patients 25 15

What Does the Entire Network Look Like?

Entire Network

How Are Infected Contacts Related to the Cases?

Case-patients and LTBI

Which Contacts Should We Pursue for More Information?

Network Core

How Do You Prioritize?

Contacts Needing Evaluation

Conclusions

Conclusion: EPI Data Delayed diagnosis generated a large community outbreak in a low incidence area All case-patients were linked to index case-patient High TST reaction rate around the index case-patient

Conclusion: Network-Informed Approach Proved feasible in a low incidence setting Required no new data; based on routine contact investigations Facilitated discussions between state and county TB controllers

Acknowledgments McKenzie Andre, MD Epidemic Intelligence Service Officer Division of TB Elimination CDC Local and State TB Control Authorities Valdis E. Krebs InFlow Software™