More than 500,000 Yemenis have been infected with cholera this year, and nearly 2,000 have died, the World Health Organization said Monday.

Cholera is endemic in Yemen, which is on the tip of the Arabian Peninsula and across the Gulf of Aden from Somalia. But the disease, caused by a bacterium in contaminated water, has spread rapidly since April.

Civil war and bombing by neighboring Saudi Arabia have crippled much of the country’s water-distribution system, destroyed hospitals and forced vast numbers of people to flee their homes.

By contrast, cholera has killed about 10,000 people in Haiti since it was reintroduced by United Nations peacekeepers in 2010, triggering that country’s first outbreak in 50 years.