[Source: Emerging Infectious Diseases Journal, full page: (LINK). Extract, edited.]

Seroprevalence of Crimean-Congo Hemorrhagic Fever Virus, Bulgaria

To the Editor:

Crimean-Congo hemorrhagic fever (CCHF) is endemic in southern Russia, southeastern Europe, Africa, the Middle East, and southwestern Asia (1). The incidence and spread of the disease have increased in recent years. In Bulgaria, located on the Balkan Peninsula, CCHF is endemic. The disease was first described in the country in 1952 (3). Since then, a mandatory reporting system has been introduced. Most of Bulgaria is an ecologically favorable environment for CCHF virus (CCHFV) circulation in nature. In the 1970s, numerous virologic and serologic studies were performed by Vasilenko et al., who showed that the most affected age group was 2150 years and that most of those with CCHF were male (65%) (cited in [2]). A genetic study showed that CCHFV strains in Bulgaria cluster together with strains from other Balkan countries and Russia (3). A vaccine consisting of chloroform-inactivated CCHFV was developed in 1974, and the currently used vaccine strain, isolated from a Bulgarian patient, was characterized genetically (4).