Haiti has launched a massive cholera vaccination campaign in parts of the country devastated by Hurricane Matthew.
The campaign, begun Tuesday, is expected to be the world's largest, targeting 820,000 people.
There have been around 3,500 suspected cases of the water-borne illness since the Category 4 storm tore across southwest Haiti last month. It created ideal conditions for the spread of cholera by destroying water supplies and forcing people who lost homes to squeeze into overcrowded shelters. The government says the storm killed 546 people.
Haiti has battled a cholera outbreak since 2010, when the bacteria was imported into the country by a contingent of United Nations peacekeepers. Since then, the illness has sickened more than 800,000 people and killed about 9,000.
The campaign will mark the first time that so many people will be given only one dose of the cholera vaccine. Normally, the vaccine is given in two doses.
But a previous initiative conducted by Doctors Without Borders in South Sudan found that a single dose of the cholera vaccine proved to be extremely effective at boosting immunity, according to a study published in the medical journal The Lancet in November.