Comparing Shigella waterborne outbreaks in four different areas in Greece: common features and differences.

In Greece the public health surveillance for most infectious diseases, including shigellosis, is not well developed. However, four waterborne outbreaks of shigellosis have been recorded in Greece in the last three decades, in different areas of the country, under different environmental and socioeconomic conditions. This study presents the epidemiological characteristics of these four outbreaks in order to examine common points and differences and to investigate their possible association with environmental and socioeconomic conditions. All four outbreaks were caused by Shigella sonnei and related to drinking water. Epidemic curves, distribution of cases by age and gender, hospitalization rates, environmental conditions and laboratory results were compared. The outbreaks seemed to correspond to two different 'models' presenting two characteristic types of epidemic waves related to specific environmental conditions. The attack rates for the general population varied from about 9 to 13% and were similar for both sexes. Children were affected mostly. In these outbreaks there was a strong suspicion of contamination of the water distribution system from the sewage network, highlighting the importance of environmental health control measures.