1. Laboratory of Virology, University Hospital “St. Marina”, Varna, Bulgaria
2. Department of Microbiology and Virology, Faculty of Medicine, Medical University of Varna, Varna, Bulgaria
3. Department of General and Clinical Pathology, Faculty of Medicine, Medical University of Varna, Varna, Bulgaria
4. Training Sector of Medical Laboratory Assistant, Medical College, Medical University of Varna, Varna, Bulgaria