Availability of safe drinking-water: the answer to cholera outbreak? Nabua, Camarines Sur, Philippines, 2012

In May 2012, there were increasing diarrhoea cases and deaths reported from Nabua, Camarines Sur to the Philippines event-based surveillance system. An investigation was conducted to identify risk factors and determine transmission dynamics.

A suspected case was defined as a resident of Nabua with at least three episodes of watery diarrhoea per day from 16 March to 22 June 2012. A confirmed case was defined as a suspected case positive for Vibrio cholerae. An environmental investigation was conducted and rectal swabs and water samples sent to the national reference laboratory for bacterial isolation. A 1:2 case-control study matching for age and sex was conducted. Data were analysed using Epi Info.

There were 309 suspected cases with two deaths, and the most affected age group was children under five years (45%). Eight cases were positive for Vibrio cholerae Ogawa El Tor and one for Non-01. Water samples were positive for faecal coliforms and Aeromonas caviae. The case-control study showed that cases had a higher odds than controls of using unchlorinated water sources (odds ratio [OR] = 3.6; 95% confidence interval [CI]:1.6-8.5) and having toilets located within 20 m of a septic tank (OR = 2.7; 95% CI: 1.4-5.3). In multivariate analysis, the only significant factor was drinking from piped water (OR = 0.21; 95% CI: 0.09-0.49).

In this cholera outbreak, drinking-water from unchlorinated wells was a significant risk factor. Future cholera control efforts should include not just improving water and sanitation systems but also intensified behaviour change campaigns.