Peter Schlattmann

RATIONALE: Reducing the global burden of sepsis, a recognized global health challenge, requires comprehensive data on the incidence and mortality on a global scale. OBJECTIVES: To estimate the worldwide incidence and mortality of sepsis and identify knowledge gaps based on available evidence from observational studies. METHODS: We systematically searched 15 international citation databases for population-level estimates of sepsis incidence rates and fatality in adult populations using consensus criteria and published in the last 36 years. MEASUREMENTS AND MAIN RESULTS: The search yielded 1,553 reports from 1979 to 2015, of which 45 met our criteria. A total of 27 studies from seven high-income countries provided data for metaanalysis. For these countries, the population incidence rate was 288 (95% confidence interval [CI], 215-386; τ = 0.55) for hospital-treated sepsis cases and 148 (95% CI, 98-226; τ = 0.99) for hospital-treated severe sepsis cases per 100,000 person-years. Restricted to the last decade, the incidence rate was 437 (95% CI, 334-571; τ = 0.38) for sepsis and 270 (95% CI, 176-412; τ = 0.60) for severe sepsis cases per 100,000 person-years. Hospital mortality was 17% for sepsis and 26% for severe sepsis during this period. There were no population-level sepsis incidence estimates from lower-income countries, which limits the prediction of global cases and deaths. However, a tentative extrapolation from high-income country data suggests global estimates of 31.5 million sepsis and 19.4 million severe sepsis cases, with potentially 5.3 million deaths annually. CONCLUSIONS: Population-level epidemiologic data for sepsis are scarce and nonexistent for low- and middle-income countries. Our analyses underline the urgent need to implement global strategies to measure sepsis morbidity and mortality, particularly in low- and middle-income countries.

Wolbachia are intracellular bacteria found in many species of arthropods and nematodes. They manipulate the reproduction of their arthropod hosts in various ways, may play a role in host speciation and have potential applications in biological pest control. Estimates suggest that at least 20% of all insect species are infected with Wolbachia. These estimates result from several Wolbachia screenings in which numerous species were tested for infection; however, tests were mostly performed on only one to two individuals per species. The actual percent of species infected will depend on the distribution of infection frequencies among species. We present a meta-analysis that estimates percentage of infected species based on data on the distribution of infection levels among species. We used a beta-binomial model that describes the distribution of infection frequencies of Wolbachia, shedding light on the overall infection rate as well as on the infection frequency within species. Our main findings are that (1) the proportion of Wolbachia-infected species is estimated to be 66%, and that (2) within species the infection frequency follows a 'most-or-few' infection pattern in a sense that the Wolbachia infection frequency within one species is typically either very high (>90%) or very low (<10%).