Letter to the Editor Environmental Factors Influencing Epidemic Cholera Dear Sir: We have concerns with the recent publication by Jutla and colleagues, which aims to describe the environmental factors influencing epidemic cholera. 1 Regarding cholera in Haiti, the authors challenged the findings of many studies showing that the epidemic likely originated from the importation of toxi-genic Vibrio cholerae by Nepalese peacekeepers in October 2010. 2–5 Instead, they attempted to show that environmental conditions conducive to rapid growth and transmission of V. cholerae played a substantial role in epidemic onset. Their hypothesis is based on the claim that increased temperatures and rainfall during the months preceding the epidemic favored the proliferation of V. cholerae in the Haitian waters and its subsequent transmission to the local population 1 ; we believe their claims are based on misinterpretations of our published data and statistical correlations that fail to establish causality. Our field investigation of the Haitian cholera epidemic has clearly indicated that outbreaks started in Meye, near Mirebalais, before subsequently spreading downstream, following the Artibonite River. 2 Using a Spearman's rank statistical test, Jutla and colleagues stated that the correlation between cholera cases in Mirebalais and the Lower Artibonite was " very high, " thereby inferring that the epidemic started simultaneously in the two locations. 1 According to our report, each of the Lower Artibonite communes displayed a markedly higher correlation with the other Lower Artibonite communes than with Mirebalais. 2 Therefore, we did not report a strong correlation between Mirebalais and the Lower Artibonite communes , as claimed by Jutla and colleagues. 1 Nevertheless, correlation analyses are irrelevant to question the chronological progression of the epidemic. Indeed, our field investigation revealed that no suspected cases of cholera or severe diarrhea were reported in the Lower Artibonite before October 19, although the epidemic began on October 14 near Mirebalais. 2