Salmonella Outbreaks in Low- and Middle-Income Countries over the Last Decade: A Systematic Review and Meta-Analysis of Transmission Dynamics, Clinical Outcomes, and Antimicrobial Resistance.

BACKGROUND

Salmonella outbreaks persist as a public health burden in low- and middle-income countries (LMICs), yet comprehensive synthesis of their epidemiology over the past decade remains limited.

METHODS

Following PRISMA 2020 guidelines, we searched PubMed, Scopus, Web of Science, and Google Scholar for laboratory-confirmed Salmonella outbreaks in LMICs (1 January 2016-1 January 2026). Random-effects meta-analysis estimated pooled prevalence rates, with statistical heterogeneity quantified using I2 statistic. Given extreme heterogeneity across most outcomes (I2 > 90%), we present individual study ranges alongside pooled estimates.

RESULTS

Twenty-four studies from 14 LMICs met inclusion criteria. Salmonella Typhi was the predominant pathogen (70.8% of outbreaks). Waterborne transmission was most frequent (37.5%), predominating in Africa (83.3%), whereas foodborne and fecal-oral routes were common in Asia. Pooled laboratory confirmation rate was 28.02% (95% CI: 12.2-52.1; observed range: 1.5-100%), varying by region: Southeast Asia 54.2% (95% CI: 4.3-96.9), Western Pacific 27.6% (95% CI: 8.0-56.9), and Africa 6.1% (95% CI: 5.3-6.9). The pooled case fatality rate was 7.0% (95% CI: 3.4-13.7; range: 3.6-10.0%). Fever (93.0%), abdominal pain (53.6%), and headache (52.0%) were most common symptoms. Pooled antimicrobial resistance reached 59.3% (95% CI: 26.6-85.4%), highest for trimethoprim-sulfamethoxazole (94.2%) and ciprofloxacin (61.3%). Extreme heterogeneity and wide confidence intervals were observed across some pooled estimates and should be interpreted with caution.

CONCLUSIONS

Salmonella outbreaks in LMICs are characterized by high S. Typhi prevalence and predominant waterborne transmission. Elevated mortality and widespread first-line antibiotic resistance show the need for improved WASH infrastructure, enhanced real-time outbreak surveillance, and revised empiric treatment protocols.