Geneva: The World Health Organization (WHO) is sending 1 million doses of cholera vaccine to Haiti, where more than 200 cases of the killer disease have been reported since Hurricane Matthew.

The campaign is aimed at quashing new outbreaks before the peak transmission of cholera in the Caribbean country which is from November to January, during the rainy season.

"The top priority clearly for those people affected by the hurricane is to give them access to safe water. That's the only way we can control cholera," Dominique Legros, WHO cholera expert, told a news briefing on Tuesday before traveling to Port-au-Prince.

Those already infected with cholera need treatment, but a quarter of the health centers in Haiti's hard-hit southern area have been destroyed or seriously damaged, he said.

The powerful hurricane slammed into Haiti last week, killing at least 1,000 people according to a tally of numbers from local officials.

Cholera causes severe diarrhea and can kill within hours if untreated. It is spread through contaminated water and has a short incubation period, which leads to rapid outbreaks.

Some 150 suspected cholera cases have been reported in Grande'Anse department and 50 in South department since the hurricane struck, Legros said, calling it a "sharp increase compared to usual figures".

He had no death figures.

A further 28 cholera cases have been reported in Artibonite and six cases in North West, the WHO said.

Cholera was introduced to Haiti accidentally by U.N. peacekeepers who dumped sewage into a river after the 2010 earthquake. The outbreak has since infected hundreds of thousands of people - including an annual average of about 800 since 2014 - and killed more than 9,000.

WHO, which has deployed 80 staff to Haiti, was considering giving people a single dose of the vaccine rather than the classic double dose, to cover more people, albeit it with a shorter protection period, Legros said.

"So far we have one experience of a large-scale campaign with a single dose, it was done inBangladesh two years ago. It proved effective for six months," Legros said.

"After six months, you still have about 60 to 70 percent efficacy (of the vaccine) for severe cases of cholera, those are the ones we're interested in."