Environmental correlates of crimean-congo haemorrhagic fever incidence in Bulgaria

Abstract

BackgroundCrimean-Congo Haemorrhagic Fever (CCHF) is a zoonotic viral disease transmitted by ixodid tick bites, mainly of Hyalomma spp., or through contact with blood/tissues from infected people or animals. CCHF is endemic in the Balkan area, including Bulgaria, where it causes both sporadic cases and community outbreaks.MethodsWe described trends of CCHF in Bulgaria between 1997 and 2009 and investigated the associations between CCHF incidence and a selection of environmental factors using a zero-inflated modelling approach.ResultsA total of 159 CCHF cases (38 women and 121 men) were identified between 1997 and 2009. The incidence was 0.13 cases per 100,000 population/year with a fatality rate of 26%. An epidemic peak was detected close to the Turkish border in the summer of 2002. Most cases were reported between April and September. Increasing mean temperature, Normalized Difference Vegetation Index (NDVI), savannah-type land coverage or habitat fragmentation increased significantly the incidence of CCHF in the CCHF-affected areas. Similar to that observed in Turkey, we found that areas with warmer temperatures in the autumn prior to the case-reporting year had an increased probability of reporting zero CCHF cases.ConclusionsWe identified environmental correlates of CCHF incidence in Bulgaria that may support the prospective implementation of public health interventions.

Crimean-Congo hemorrhagic fever and its relationship with climate factors in southeast Iran: a 13-year experience

“…This result is similar to previous studies in Iran, Turkey, and Bulgaria [3,6,11] and corresponds closely with the months that the temperature is between 30°C and 40°C and maximum humidity is between 20% and 50% (the favorite condition of Hyalomma ticks) in southeast Iran. It should be noted that the pattern of CCHF distribution on the other side of the border (in the Baluchistan province of Pakistan) is somewhat different from the results of our study, with two annual surges in April and August [20] and very few cases seen during the rest of the year.…”

“…This result is somewhat similar to a previous study conducted in Bulgaria that described the trends of CCHF between 1997 and 2009 [6]. However, in a Turkish study, the number of cases increased dramatically from 2004 to 2007 [3].…”

“…Several studies have discussed the relationship between the climatic factors and the vector's lifecycle, ecological conditions, and, consequently, the occurrence of CCHF in human populations [1,[4][5][6]. In addition to climate variables, there are some other epidemiologic factors that influence the occurrence of CCHF that should be considered in controlling the disease [7][8][9].…”

Non-fatal case of Crimean-Congo haemorrhagic fever imported into the United Kingdom (ex Bulgaria), June 2014

“…CCHF is considered endemic in several parts of the Balkans, with over 1,500 human cases registered in Bulgaria up to 2009 [17,18]. Seroprevalence studies have shown human exposure to CCHFV in numerous districts across the country, with the highest rates in the Burgas region, where the UK traveller in this report was based [19].…”

An Emerging Threat of Crimean Congo Hemorrhagic Fever: Call for Preparedness

“…CCHF is endemic in Europe and Bulgaria however outbreaks have been recorded in other countries like Kosovo, Turkey, Albania, Ukraine and South-west of the Russian Federation with increased number of cases . In Bulgaria, totally 159 CCHF cases were identified between 1997 and 2009 (Vescio et al, 2012). Between 2002 and 2009 increased numbers of CCHF cases were reported from Turkey (Ozdarendeli et al, 2010).…”