Sierra Leone suspected typhoid notifications exceed regional blood-culture benchmark

Routine suspected typhoid notification rates in Sierra Leone exceeded an African blood-culture surveillance estimate in every year from 2019 through 2025, according to an observational analysis of the country’s electronic Integrated Disease Surveillance and Response system. The study covered 112 district-year records from all 16 health districts and recorded 1,016,325 suspected typhoid notifications. Annual national rates were 1,290 per 100,000 population in 2019 and 2,054 per 100,000 in 2025. For comparison, investigators used 535 per 100,000 person-years, the upper 95% confidence limit of the highest adjusted all-age site estimate from the Typhoid Fever Surveillance in Africa Program. Annual rate ratios relative to that reference ranged from 2.41 to 3.84. Because the routine records were not linked to diagnostic methods or microbiological results, the analysis measured suspected notifications rather than culture-confirmed incidence.

The researchers calculated annual district and national notification rates from suspected typhoid counts and projected populations. They used a district-clustered Poisson generalized estimating equation to estimate annual rates, 95% confidence intervals and rate ratios against the blood-culture-derived reference, accounting for repeated observations within districts. Geographic analysis described variation among health districts. The study was designed to compare routine surveillance data with the African blood-culture estimate and determine how closely the two measures aligned; it could not establish what proportion of reported notifications represented laboratory-confirmed typhoid. Sierra Leone’s eIDSR collects aggregate district notifications without connecting individual reports to blood-culture, polymerase chain reaction or rapid diagnostic test results.

For every study year, the district-clustered 95% confidence interval for the national notification rate was above the reference value of 535 per 100,000 person-years. All seven comparisons remained statistically significant after Holm adjustment for multiple testing, with adjusted two-sided p values below 0.002. The rate ratios show that annual routine notification rates were between 2.41 and 3.84 times the selected benchmark. District-level rates in 2025 ranged from 43 to 5,116 per 100,000 population, revealing substantial geographic variation beneath the national figures. This range is a cross-sectional comparison among districts in one year and does not by itself establish that notification rates increased or decreased over time within any district.

The investigators also tested whether within-district changes in clinical malaria notification rates were associated with changes in suspected typhoid notification rates. A secondary negative-binomial generalized estimating equation estimated the association. A doubling of the clinical malaria notification rate was associated with a typhoid rate ratio of 1.44, with a 95% confidence interval of 0.87–2.39 and p = 0.14. The confidence interval included 1, and the association was not statistically significant, so the analysis did not provide strong evidence of a relationship between the two notification measures. This model examined district-level patterns and does not establish that changes in one disease caused changes in the other.

The findings identify a persistent discrepancy between Sierra Leone’s routine suspected typhoid notifications and an African estimate based on blood-culture surveillance. The authors cautioned that the higher routine rates could reflect true transmission, diagnostic classification, care seeking, reporting practices or combinations of these processes. The data therefore do not show that Sierra Leone’s underlying culture-confirmed typhoid burden was conclusively 2.41 to 3.84 times the regional benchmark. To determine how routine notifications relate to confirmed disease, the study calls for standardized screening of febrile patients, sentinel blood-culture surveillance, and review of clinical registers and eIDSR records in both high- and low-notification districts. Until such diagnostic comparisons are available, the national figures should be interpreted as rates of suspected typhoid notification, not direct measurements of confirmed incidence.

Subject of Research: Comparison of Sierra Leone suspected typhoid notification rates with African blood-culture surveillance estimates

Article Title: Routine suspected typhoid notification rates in Sierra Leone exceed African blood-culture surveillance estimates, 2019–2025

Article References: Ikoona, E. N., Namulemo, L., Magoba, B., Sinnah, M. M., Vandi, M. A., & Sahr, F. (2026). Routine suspected typhoid notification rates in Sierra Leone exceed African blood-culture surveillance estimates, 2019–2025. BMC Infectious Diseases. https://doi.org/10.1186/s12879-026-14325-z

Image Credits: AI Generated

DOI: 10.1186/s12879-026-14325-z

Keywords: Sierra Leone, typhoid, suspected notifications, blood-culture surveillance, eIDSR, notification rates, district variation, epidemiology, malaria notifications, surveillance, Routine, suspected