Thirteen people have died of cholera in the northeast Nigerian state of Yobe in the past week, the state health commissioner said on Friday, blaming the outbreak on contaminated water. Yobe is among the three states worst-hit by the Boko Haram insurgency, with many people living in camps where they lack sufficient food and are at risk of disease.Last year, scores of people died of cholera in camps for internally displaced people, prompting the World Health Organisation (WHO) to launch a massive vaccination campaign in the region."We have recorded 13 fatalities in the cholera outbreak in Gashua town under Bade local government area within the past week. A total of 159 cases were recorded," Yobe state health commissioner Mohammad Bello Kawuwa told AFP. "We were able to trace the source of the outbreak to water contamination. Samples from five boreholes in the town tested positive," he said. Kawuwa said the outbreak had been confined to areas where five shallow boreholes were dug. "We sent in rapid response team who have been able to contain the outbreak. The teams distributed water sterilisation tablets in the affected communities and disinfected water sources and lavatories". Cholera is transmitted through contaminated drinking water and causes acute diarrhoea, with children facing a particularly high risk of infection. Water-borne diseases are a constant threat because of a lack of adequate sanitation as well as stagnant groundwater during the rainy season in Nigeria.KEEP UPDATED on the latest news from around the continent by subscribing to our FREE newsletter, Hello Africa.FOLLOW News24 Africa on Twitter and Facebook.