Researchers estimating cholera incidence in endemic areas have found that the disease has a substantial burden, with the highest impact on young children.
Such estimates are important, they say, in deciding where interventions — such as water supply and sanitation improvement, and vaccination — should be targeted.
Published in PLoS Neglected Tropical Diseases this month (20 February), the study was carried out in three sites — Kolkata in India, Jakarta in Indonesia, and Beira in Mozambique.
The international team tested for cholera — caused by the bacterium Vibrio cholerae — among people of all age groups who presented with diarrhoea at health centres in these areas.
They found that the lowest overall cholera rate was in Jakarta, with 0.5 cases per 1000 people per year. The incidence was three times higher in Kolkata (1.6 per 1000 people per year) and eight times higher in Beira (four per 1000 people per year).
In all sites, children were the most affected, with rates highest in those children under five years of age.
"The study implies that cholera is still a major problem in developing countries, which many scientists and policymakers are not aware of," Dipika Sur, an author of the study and deputy director at the National Institute of Cholera and Enteric Diseases in Kolkata, told SciDev.Net.
Sur says that children tend to have the disease more in endemic areas because adults develop immunity, but children, being newly exposed, do not yet have this immunity.
Providing safe water and sanitation to Kolkata's huge population is not feasible in the near future, says Sur. "Vaccination is an attractive alternative. However low cost cholera vaccines are not yet available."
Jo Barnes from the Faculty of Health Sciences at Stellenbosch University, South Africa, says Mozambique is at high risk from cholera due to ongoing flooding and poor infrastructure.
"People have been displaced and are living in refugee-like accommodation – it's a situation ripe for cholera." The disease can remain dormant in the environment for years, she warns, and resurface as soon as conditions are right.
But, she says, vaccination against the disease would be ineffective. "The vaccinations only work for three to six months and are only 50 per cent effective. What is needed urgently are pit latrines, clean drinking water and education about hygiene."