COTONOU, 2 February 2010 (IRIN) - In Benin cholera has killed five people in the past two weeks in a rare dry-season outbreak. Health officials detected the first cases of the diarrhoeal disease on 13 January in the town of Bonou - 90km east of the economic capital Cotonou - where 66 cases and four deaths were recorded up to 29 January, according to the Health Ministry's director of sanitation Laurent Assogba. Three cases, one resulting in death, have also been recorded in Cotonou, he said. Cholera generally spreads during the rainy season when flooding can contaminate water sources. The World Health Organization (WHO) says cholera in the dry season is uncommon but it does occur. "Cholera is not transmitted only via water during heavy rains," Aristide Roch Sossou of WHO-Benin told IRIN. "Foods [kept in unhygienic conditions] and dirty hands are also factors favouring cholera bacteria." He said studies are underway to identify the source and transmission mode of the bacteria in the latest outbreak. "We have no evidence for the causes of cholera during dry season," Geneva-based WHO cholera expert Claire-Lise Chaignat told IRIN. "It may well be that the vibrio germ is being introduced by contaminated people, or it could be present in boreholes." Benin's Health Ministry is telling citizens to be extra vigilant. Anyone in and around Bonou with vomiting or diarrhoea "must go directly to a health centre", Assogba said. Health officials are also advising people to observe proper hygiene - including thoroughly washing hands and food. In 2009 during the rainy season at least 70 people died of cholera in Benin, according to the Health Ministry.