An Epidemiological Study of Aeromonas spp. Infections in Norway

Aeromonas spp. is ubiquitous in aquatic habitats causing a wide range of infections in humans after exposure to contaminated water or food. We conducted an epidemiological study of Aeromonas infections detected in Norway, using laboratory-based surveillance data during 2014-2018, in order to identify risk factors associated with developing a severe infection. We identified 503 Aeromonas cases over a 5-year period with an average incidence of 1.9 per 100,000 inhabitants per year. Aeromonas mostly caused gastrointestinal infections (69.8%, n=351), followed by wound (8.6%, n=43) and blood infections (7.4%, n=37). Gastrointestinal and wound infections peaked in the summer months. Major isolated species were A. hydrophila (15.3%), A. veronii (10.7 %), and A. caviae (10.7%). Hospitalisation was reported for 81.1% of blood infections (n=30), 51.2% of wound infections (n=22) and 23.1% of gastrointestinal infections (n=81). Risk factors for gastrointestinal infections associated with hospitalisation were (i) age group 65-79 years old (adjOR=3.10; 95% CI: 1.39-6.93) and >80 years old (adjOR=17.66; 95% CI: 5.05-61.79) and (ii) infections caused by A. caviae (adjOR=3.26; 95% CI: 1.3-8.1). This study showed that Aeromonas infections are common throughout the years suggesting a diverse and continuous source of exposure. Future research on environmental sources and preventive measures particularly for severe Aeromonas infections is recommended.