Transmission network analysis to complement routine tuberculosis contact investigations

Abstract

Objective: We examined the feasibility and value of network analysis to complement routine tuberculosis (TB) contact investigation procedures during an outbreak.

Methods: We reviewed hospital, health department, and jail records and interviewed TB patients. Mycobacterium tuberculosis isolates were genotyped. We evaluated contacts of TB patients for latent TB infection (LTBI) and TB, and analyzed routine contact investigation data, including tuberculin skin test (TST) results. Outcomes included number of contacts identified, number of contacts evaluated, and their TST status. We used network analysis visualizations and metrics (reach, degree, betweenness) to characterize the outbreak.

Results: secondary TB patients and more than 1200 contacts. Genotyping detected a 21-band pattern of a strain W variant. No HIV-infected patients were diagnosed. Contacts prioritized by network analysis were more likely to have LTBI than nonprioritized contacts (odds ratio=7.8; 95% confidence interval=1.6, 36.6). Network visualizations and metrics highlighted patients central to sustaining the outbreak and helped prioritize contacts for evaluation.

Conclusions: A network-informed approach to TB contact investigations provided a novel means to examine large quantities of data and helped focus TB control.

FIGURE 1—

Visualization of the identified links among the first 35 tuberculosis patients during an outbreak investigation in southwest Oklahoma, 2002. Note. This diagram was compiled using only the existing contact investigation records obtained before or during the Centers for Disease Control and Prevention on-site investigation. Tuberculosis patients are represented by black boxes. Gray lines represent the links between patients. Decreasing thicknesses of gray lines represent the strength of relationship between patients: close, casual, or undetermined, respectively.

FIGURE 2—

Visualization of the first 35 tuberculosis (TB) patients and their 1039 contacts, southwest Oklahoma, 2002. Note. TB patients are represented by black boxes. Contacts are represented by white boxes. Gray lines represent the links between TB patients and contacts. Decreasing thicknesses of gray lines represent the strength of the relationship between patients and type of contacts: close, casual, or undetermined, respectively.

FIGURE 3—

Visualization of the first 35 tuberculosis (TB) patients and all contacts in need of clinical evaluation for TB and latent TB infection in southwest Oklahoma, 2002. Note. Critical contacts with high betweenness and reach centrality metrics are indicated. TB patients are represented by black boxes with 1- or 2-digit numbers. Gray boxes with 4-digit numbers represent unevaluated contacts at the time of CDC investigation. White boxes with 4-digit numbers represent priority contacts. Contacts surrounded by dashed boxes are those with high betweenness. Gray lines represent the links between contacts and patients. Decreasing thicknesses of gray lines represent the strength of the relationship between patients and type of contacts: close, casual, or undetermined, respectively.