1. European Programme for Intervention Epidemiology Training (EPIET), European Centre for Disease Prevention and Control (ECDC), Stockholm, Sweden
2. National Institute of Public Health - National Institute of Hygiene, Department of Epidemiology, Warsaw, Poland
3. District Sanitary Station, Department of Epidemiology, Otwock, Poland
4. National Institute of Public Health - National Institute of Hygiene, Department of Bacteriology, Warsaw, Poland