Virus infection significantly decreases insect fitness: a meta-analysis

Abstract Organisms are constantly at risk of being infected by pathogens such as viruses, which can impose substantial fitness costs on hosts. In insects, viral infections are widespread, yet the magnitude of their effects on host fitness and the factors shaping this variation remain poorly quantified. Here, we conducted a meta-analysis to assess the degree to which viral infection affects the fitness (survival and fecundity) and fitness-related traits (development time and body size) of insect hosts, and which factors may influence the impact of viral infection on hosts, such as whether the insect host is a disease vector and whether the insect is new or the natural host of the virus. We gathered 953 effect sizes from 145 studies. Overall, viruses significantly reduce host fitness, especially their survival. The reduction in fitness was higher in non-vector than in vector insects, and no difference was observed between infections in new and natural hosts. These findings show that viruses exert severe harmful effects on hosts by decreasing their fitness. More broadly, our findings highlight the potential for viral infection in wild insect populations to influence the occurrence and persistence of symbiotic bacteria, such as Wolbachia.