1. Faculty of Medicine, University of Latvia, LV-1004 Riga, Latvia
2. Department of Internal Medicine, Pauls Stradins Clinical University Hospital, LV-1002 Riga, Latvia
3. Laboratory for Statistical Research and Data Analysis, Faculty of Physics, Mathematics and Optometry, University of Latvia, LV-1004 Riga, Latvia
4. Department of Infectious Diseases and Hospital Epidemiology, Pauls Stradins Clinical University Hospital, LV-1002 Riga, Latvia