Predictors and risk factors of typhoid fever in urban informal settlements of Nairobi, Kenya.

A clear understanding of the risk factors and key predictors of typhoid fever in endemic, low-resource settings is essential for informing effective prevention strategies and guiding empiric patient management. This study aimed to identify the predictors and risk factors linked to culture-confirmed typhoid fever in Mukuru informal settlements in Nairobi, Kenya. Between November 2020 and July 2025, patients presenting with a fever of ≥ 38 °C, and/or with diarrhea were enrolled at seven health facilities in the Mukuru settlements. Structured questionnaires and case report forms were used to collect socio-demographic, environmental, and clinical data. Blood and stool cultures were performed to confirm the presence of Salmonella Typhi (S. Typhi). The associations between potential risk factors and typhoid positivity were analysed using chi-square tests and multivariable logistic regression to estimate adjusted odds ratios (aOR) with 95% confidence intervals (CI). Of the 8,950 patients enrolled, 131 (1.46%, 95% CI:1.23-1.73%) had S. Typhi positive blood culture. In the adjusted analysis, patients aged 5-16 years (aOR 2.50, 95% CI 1.55-4.04) and those over 16 years (aOR 2.16, 95% CI 1.41-3.31) had significantly higher odds of typhoid infection compared to children under five. Continuous fever (fever ≥ 38 °C for the last 3 days) (aOR 3.48, 95% CI 2.11-5.73), vomiting (aOR 1.89, 95% CI 1.29-2.75), moderate dehydration (aOR 2.95, 95% CI 1.25-6.95), and headache (aOR 1.68, 95% CI 1.12-2.53) were independently associated with typhoid infection. Households with two or more children under five years had increased odds of infection (aOR 1.98, 95% CI 1.28-3.07). Usage of a shared flush toilet was significantly associated with increased odds of typhoid infection (aOR = 2.42, 95% CI: 1.69-3.47, p < 0.001). Our findings demonstrate that typhoid fever in Mukuru informal settlements is driven by factors such as age, unsafe water practices, and shared sanitation. Interventions, such as strengthening water, sanitation, and hygiene (WaSH) infrastructure and practices are vital to reducing typhoid fever risk in these endemic settings.