Trends in Human Leptospirosis in Denmark, 1980 to 2012

Leptospirosis in humans is a mandatory notifiable disease in Denmark. To identify changing trends in human leptospirosis in Denmark, we analysed data from the passive laboratory surveillance and clinical notifications from a 32-year period (1980-2012). In that period, 584 cases of leptospirosis were laboratory-diagnosed, an average annual incidence rate of 0.34 cases/100,000 population (range: 0.07-1.1/100,000 population). Seventy per cent of patients were male. Overall, Patoc was the predominant serogroup diagnosed (32%) but over time, the Leptospira serogroup distribution has changed. In recent years Icterohaemorrhagiae and Sejroe have been diagnosed most frequently, in contrast to Patoc and Sejroe in earlier years. Notification data for 170 cases showed that work-related exposures were reported in 48% of infections, with fish farming (44%) and farming (22%) as the most frequently mentioned professions. Other common exposures were related to travel (13%), recreation (8%) and sewage (7%). Geomapping of cases showed a geographical clustering for some exposures. Future preventive measures could include raising awareness among clinicians about the risks and prevention of exposure in specific groups (fish farmers, farmers and travellers) to reduce leptospirosis in Denmark. .