The World Health Organisation said it would send a million cholera vaccine doses to Haiti, which has seen cases of the disease surge since it was ravaged by Hurricane Matthew on 28 September 2016.
A 'sharp increase' in cases
The storm, which has killed at least 372 people in the impoverished Caribbean nation, came as Haitians were already struggling with the intestinal disease spread by contaminated food and water.
WHO cholera expert Dominique Legros told reporters in Geneva there had already been "a sharp increase" in cases in the south of the country, with 148 cases detected in the Grand'Anse department and 53 more in the South department.
The potential for a reinvigorated cholera outbreak is especially alarming for Haiti, which has grappled with the disease since the aftermath of its catastrophic earthquake in 2010.
Since then, around 10,000 people have died from the disease, and on average some 500 new cases have been reported every week over the past six years.
New cases had already begun rising before the hurricane, with 29,000 reported since the beginning of the year, an average of nearly 800 a week, the WHO said.
Large-scale immunisation campaign
The hurricane, which fouled water sources, hit Haiti just as the country was approaching the period of the year when it generally counts most cholera cases, Legros said.
Making matters worse, the storm damaged around a quarter of all health facilities in the south of the country, making it more difficult for cholera patients to get treatment.
To try to halt the spread of the deadly disease, the WHO has decided to send one million vaccine doses to Haiti for a large-scale immunisation campaign, he said.
Two doses of the vaccine are needed to offer full protection, but Legros said the WHO and the Haitian government were considering a one-dose campaign in a bid to reach more people.
Legros explained that one dose of the vaccine had been shown to offer full protection for about six months, with the effect fully disappearing within about a year.
He said this should be "enough to cover the period most at risk".
Before the hurricane, some 400,000 people had already received a double dose of the vaccine since 2013, he said.