Age-stratified epidemiological and clinical predictors of laboratory-confirmed measles among suspected cases in Diyarbakır, Türkiye (2012-2024): a test-negative case-control study.

BACKGROUND

Measles elimination remains elusive in many countries, and resurgences occur even in previously controlled settings. We assessed age-specific clinical and epidemiological factors associated with laboratory-confirmed measles among suspected cases.

METHODS

In this test-negative case-control study, we analyzed surveillance data from Diyarbakır, Türkiye (2012-2024). Cases and controls were defined by measles-specific IgM results. Cases were stratified into two age groups, individuals aged ≤ 1 year and individuals aged > 1 year, with controls selected using systematic sampling at a case-control ratio of 1:3. Univariable and multivariable logistic regression analyses estimated odds ratios (ORs) for demographic factors, vaccination status, seasonality, epidemic year, clinical symptoms, and hospitalization.

RESULTS

Among 3,868 individuals (967 cases, 2,901 controls), 32% of cases were ≤ 1 year of age. In infants, predictors included hospitalization (OR: 7.95; 95% CI:4.21-15), upper respiratory tract symptoms (OR: 3.20; 95% CI:1.87-5.48), age 7-9 months (OR: 4.16; 95% CI:2.33-7.41) and 10-12 months (OR: 5.28; 95% CI:3.03-9.20), and spring-summer season (OR: 2.08; 95% CI:1.14-3.82). Among individuals aged > 1 year, significant predictors were receipt of a single dose (OR: 3.64; 95% CI:1.09-12.15); being unvaccinated (OR: 16.13; 95% CI:4.77-54.54) or having unknown vaccination status (OR: 17.26; 95% CI:5.14-57.88); epidemic year (OR: 4.06; 95% CI:2.74-6.02); spring-summer season (OR: 1.80; 95% CI:1.21-2.69); fever (OR: 1.89; 95% CI:1.20-2.95); and hospitalization (OR: 2.24; 95% CI:1.39-3.62).

CONCLUSION

Among suspected cases, age-specific predictors of laboratory-confirmed measles may support clinical suspicion, surveillance alertness, and prioritization of laboratory testing when interpreted alongside the local epidemiological context, including seasonality, vaccination coverage, and individual vaccination status. These findings may help guide regionally tailored surveillance and control efforts.