After higher rates of occupational or leisure diseases recorded in the Czech Republic in the second half of the last century it was found that the last climatic changes and catastrophic floods of 1997 and 2002 were followed by outbreaks of leptospirosis as the only re-emerging postflood infection. While in tropics and subtropics the monsoon season is typically followed by highly increased rates of leptospirosis in humans, even, with fatal outcomes, this phenomenon remained unknown under the climatic conditions of the Czech Republic where human leptospirosis has been reported rather sporadically, mostly in natural foci of infection, and its incidence rate is usually about 0.3 % per 100,000 population. Nevertheless, after the unexpected vast floods of 1997 and 2002 that also afflicted natural foci of leptospirosis, the rates of reported and serologically confirmed cases of leptospirosis in the Czech Republic were three times as high as usual with the specific morbidity reaching 0.9 case per 100,000 population. In 1997, as many as 7,156 persons were tested for leptospirosis in the Czech Republic: the disease was diagnosed and reported in 94 patients and in 2002, 92 out of 4,999 persons tested were diagnosed with leptospirosis. Two thirds of these cases were from inundation areas, half of them being directly associated with floods (exposure to residual water, flood mud in cellars, etc.). Four case of Weil disease reported in 1997 were fatal. As many as 41 deaths from Weil disease have been reported in the Czech Republic since 1963 when the disease became reportable.

        Key words: leptospirosis – epidemiology – floods.