Epidemiological Analysis of Leptospirosis in Bulgaria, 1999-2018

Abstract

Abstract Background: The aim of the study was to characterize the epidemic process of leptospirosis in Bulgaria. Material and methods: Data was collected from the National Centre for Public Health and Analysis official database of infectious diseases for the period 1999-2018 year. Graphical methods, absolute and relative values were applied when analyzing the data. A regression analysis was used to search for trends in incidence rate and mortality rate over a period of time. Results: For the period 1999-2018, a total of 414 cases of leptospirosis were registered in Bulgaria, 35 of them were lethal. Incidence ranged from 0,10 per 100 000 population (2012, 2017 year) to 0,63 per 100 000 (1999 year). Using the regression analysis method a model p = 0,03 < 0,05 was constructed, which most adequately described the tendency of leptospirosis incidence rate in Bulgaria. Mortality rate was the highest in 2000 – 0,09 per 100 000 and was zero for six years of the survey period. An adequate model was developed p = 0,005 < 0,05, which showed the trend of leptospirosis mortality rate. The case-fatality rate was high and reached 27,27% in 2010. The highest incidence rate of leptospirosis was in the areas of Yambol and Shumen. Leptospirosis in Bulgaria had a seasonal trend. Risk factors for the disease were male gender and age over 55 years. Conclusions: Global environmental changes, including extreme weather conditions, increase the threat of severe epidemics of leptospirosis worldwide. An unfavorable impact on the spread of leptospirosis is the intensive migration of the population and travel-associated cases. Modern control over leptospirosis should be constant, complex and ubiquitous. Therefore, leptospirosis in Bulgaria should not be underestimated.