"In many African countries there are sporadic cases during the year, then the weather changes or other conditions change, and all of a sudden there is an outbreak," Dr Vasset says, adding that the disease is difficult to predict.
Sarah Morgan, Senior Health Programme Adviser at aid agency World Vision, agrees that it is possible low-level cholera was present in Haiti all along.
"Surveillance data on cholera in Haiti are not available," she says. However, watery diarrhoea has been common in the country, causing 5% to 16% of the deaths among Haitian children, according to CDC data.
With diarrhoea so prevalent and no stringent monitoring by health authorities and 80% of those with symptoms showing only moderate signs of infection, sporadic cases of cholera might not have registered.
On the rise
Cholera is widespread and on the rise, with three to five million cases worldwide, the says.
More than 100,000 people die from the disease every year, with the majority of cases in Sub-Saharan Africa. Epidemics of Vibrio Cholerae are caused by one of two strains: 01, which has been identified as the cause of the current epidemic in Haiti, and the South-East Asian strain 0139.
It is difficult to get a complete picture of the global spread of the disease, because some countries are reluctant to report cholera for fear of travel sanctions, says Adam Kamradt-Scott from the London School of Hygiene and Tropical Medicine.
Mr Kamradt-Scott points out that around 75% of people infected with Vibrio Cholerae do not develop symptoms. But they excrete the bacterium with their faeces for up to 14 days - a potential source of infection for others.
"The bacteria can be resident in water for a quite a while," Mr Kamradt-Scott explains and points to a cholera outbreak in Peru in 1991.
In Haiti, the disease has more likely been spread because people used the Artibonite river for washing and drinking.
"As soon as people have been infected and excrete the bacteria, the epidemic spreads very quickly," Mr Kamradt-Scott says.
"It is then important to break the cycle of the disease," he adds.
Because Vibrio Cholerae produces toxins that lead to watery diarrhoea, patients need to be rehydrated with liquids containing sugar and salt or with intravenous fluids.
Those infected need to receive treatment immediately, Mr Kamradt-Scott says. If not treated, the death-rate of cholera can rise up to 50%.
But the potentially deadly cholera cycle can only be broken when people also stay away from the contaminated water source until the bacteria have cleared, he adds.
25 October 2010 Last updated at 16:05 GMT
Part I Relevant Concepts and Terms
List the relevant concepts and terms in the box below. Some have been given as examples.
Part II Reflective Questions
Using the concepts and terms identified above, discussing the following questions.
-
What are the implications of the sudden cholera outbreak in Haiti on epidemic prevention?
- What can each of the stakeholders do to help prevent an outbreak of epidemic?
~~End of News Commentary Three~~