Haiti: disease model predicts more cholera and potential impact of clean water

The number of Haitians infected with cholera may reach 779,000 by the end of November 2011, nearly twice as many as UN estimates, according to a new study [1].

The UN estimate is “essentially a guess, based on no data, and ignoring the dynamics of cholera epidemics” co-author Dr. Jason Andrews told SciDev.Net.

Using a mathematical model of the epidemic, the study projects 779 000 cases of cholera and 11,100 deaths between March 1 and November 30, 2011, if there are no new interventions to curb transmission and treat victims.

The researchers estimate that 170,000 cases of cholera and 3,400 deaths could be averted by a combination of clean water, vaccination and greater distribution of antibiotics.

A 1% per week reduction in consumption of contaminated water would the greatest effect by averting 105,000 cholera cases and 1,500 deaths. Vaccination of 10% of the population would avert 63,000 cases and 900 deaths. The extension of the use of antibiotics to all patients with severe dehydration and half of patients with moderate dehydration would avert 9,000 cases and 1,300 deaths.

Andrews told SciDev.Net that the interventions could be achieved if the international community was willing to invest in them.

But Marcos Espinal, head of health surveillance, disease prevention and control at the Pan American Health Organization (PAHO), defended the UN’s approach. He told SciDev.Net that “the model used up to now is consistent with reality. We have seen just over 250,000 people with cholera in six months”.

A cholera epidemic broke out in Haiti in late October 2010, in the wake of the earthquake in January of the same year. The latest UN figures for the epidemic, published on 31 March 2011, are 267,224 cases, 4,749 deaths and a mortality rate of 1,8%.

[1] Andrews, J.R. and Basu, S. (2011). Transmission dynamics and control of cholera in Haiti : an epidemic model. The Lancet, 16 March 2011 (Article in Press). DOI: (free registration is required to view this article)

Source: María Elena Hurtado, SciDev.Net, 28 March 2011