Table 1.

Comparison of Surveillance Methods

	SETA	SEAP	SEFI	STRATAA
Design	Prospective passive, facility-based surveillance paired with population-based HCUS Prospective case-control cohort for long-term follow-up	Retrospective and prospective passive, facility-based surveillance paired with population-based HCUS	Tier 1:  Prospective population-based cohort with active surveillance Tier 2:  Prospective passive, hospital-based paired with population-based HCUS Tier 3:  Laboratory-based surveillance	Prospective population-based cohort with passive surveillance paired with population-based HCUS and seroincidence surveys
Eligibility criteria	Primary/secondary health facilities • Objective fever of ≥ 38°C OR • Subjective fever ≥ 3 consecutive days in the last week • AND reside in the nested catchment area Referral hospitals • Subjective fever ≥ 3 consecutive days in the last week, OR • Clinically suspected typhoid fever • AND reside in the catchment area • OR pathognomonic gastrointestinal perforations even in the absence of laboratory confirmation and regardless of catchment area (special cases)	Outpatient • 3 days of consecutive fever in the last 7 days • AND reside in the study catchment area • AND physician must advise blood culture Inpatient • Clinical suspicion of enteric fever AND physician must advise blood culture OR • Confirmed diagnosis of enteric fever at any time during hospitalization OR • Nontraumatic ileal perforations, even in the absence of laboratory confirmation Laboratory: • Blood culture positive for S. Typhi or S. Paratyphi A only	Tier 1 • Subjective fever ≥ 3 consecutive days (families given thermometers and diary cards to record) • AND reside in census population area • AND fever in the last 12 hours before presentation, Tier 2 • All inpatients presenting with fever OR • Patient with nontraumatic ileal perforation • AND residing in geographic catchment area Tier 3 • Blood culture positive for S. Typhi or S. Paratyphi A only	• Objective fever of ≥ 38°C OR • Subjective fever of ≥ 2 days • AND reside in census population area
Sample collection and follow-up	• Blood samples taken from enrolled subjects at baseline • For blood culture–confirmed cases of S.Typhi and iNTS and associated controls, blood, urine, and stool samples and oropharyngeal swabs were taken at day 3-7, 14, 28, 90, 180, 270, and 360• Ileal tissue or other surgical samples taken in cases of nontraumatic ileal perforation regardless of blood culture positivity • 1-year follow-up of blood culture–confirmed S.Typhi and iNTS cases and controls	• Blood samples taken from enrolled subjects at baseline • Urine samples taken from a sample of enrolled subjects at baseline • Ileal tissue samples taken in cases of nontraumatic ileal perforation regardless of blood culture positivity • 6-week phone call for blood culture–confirmed cases of S. Typhi or S. Paratyphi A—patients with complications followed up	• Blood samples taken from enrolled subjects at baseline • Ileal tissue samples taken in cases of nontraumatic ileal perforation regardless of blood culture positivity • Tier 1: Weekly follow-up, and in-person follow-up and blood collection at 28 days for enteric fever subcohort • Tier 2: Phone contact at 14 and 28 days postdischarge for cost-of-illness data	• Blood, plasma, and stool samples taken from enrolled subjects at baseline • Blood, plasma, and stool samples taken from cases and household members of culture-confirmed cases) • Day 8, 30, 180 follow-up
Incidence rate adjustment factors	• Probability of seeking care at a study facility, based on HCUS • Proportion of eligible patients enrolled in study • Proportion of eligible patients consenting to participate with a blood culture taken • Sensitivity of blood culture (assumed 60%)	• Probability of eligible patient seeking care at a study facility, based on HCUS • Proportion of eligible patients who consented and received a blood culture • Difference in healthcare-seeking according to socioeconomic status • Sensitivity of blood culture (assumed 59%)	• Probability of seeking care at a study facility, based on HCUS • Proportion of eligible patients who consented and received a blood culture • Sensitivity of blood culture (assumed 59%)	• Probability of seeking care at a study facility, based on HCUS; adjusted for the prevalence of previously identified typhoid risk factors • Proportion of eligible patients who consented and had blood drawn for culturing; adjusted for age, duration of fever, temperature at presentation, and clinical suspicion (Nepal and Bangladesh only) • Sensitivity of blood culture; adjusted for volume and reported prior antibiotic usage
Additional objectives	• Long-term sequelae, antimicrobial resistance, natural immune response, prevalence of chronic carriage, cost of illness, quality of life, long-term socioeconomic study	• Long-term sequelae, antimicrobial resistance, cost of illness	• Antimicrobial resistance • Cost of illness	• Prevalence of chronic carriage, seroincidence, antimicrobial resistance, household transmission

Abbreviations: HCUS, healthcare utilization survey; iNTS, invasive nontyphoidal Salmonella; SEAP, Surveillance for Enteric Fever in Asia Project; SEFI, Surveillance of Enteric Fever in India; SETA, Severe Typhoid Fever Surveillance in Africa; STRATAA, Strategic Typhoid Alliance Across Africa and Asia.