1. Internal Diseases, Pharmacology and Clinical Pharmacology, Pediatrics, Epidemiology, Infectious Disease, and Skin Diseases, Faculty of Medicine, Sofia University “St. Kliment Ohridski”, Sofia, Bulgaria
2. Department of Skin and Venereal Diseases, Medical Institute of the Ministry of Internal Affairs, Sofia, Bulgaria
3. Department of Infectious Diseases, Parasitology and Dermatovenereology, Medical University, Varna, Bulgaria
4. Department of Anesthesiology and Intensive Care, Medical Institute of the Ministry of Internal Affairs, Sofia, Bulgaria