[1] National Center of Infectious and Parasitic Diseases,Department of Infectious Diseases
[2] Regional Hospital Pazardzhik,Department of Epidemiology of Infectious Diseases
[3] Medical University-Plovdiv,Department of Infectious Diseases, Parasitology and Tropical Medicine
[4] Medical University-Plovdiv,Department of Infectious Diseases
[5] University Hospital for Infectious and Parasitic Diseases,Department of Infectious Diseases
[6] Regional Hospital Ruse,Department of Infectious Diseases
[7] Regional Hospital Sliven,Department of Infectious Diseases
[8] Regional Hospital Smolyan,undefined
[9] Regional Hospital Gotse Delchev,undefined