BEIRA, Mozambique — The first cases of cholera have been confirmed in the cyclone-ravaged city of Beira, Mozambique, officials announced on Wednesday, raising the stakes in an already desperate fight to help hundreds of thousands of people who lack clean water and are sheltering in increasingly squalid conditions.

The five cholera cases were discovered in Munhava, one of the poorest neighborhoods in the port city, the national director of medical assistance, Ussene Isse, told reporters. The city of some 500,000 people is still struggling to provide clean water and sanitation after Cyclone Idai roared in on March 14.

“You know, cholera is an epidemic situation. When you have one case, you expect to have more cases in the community,” Mr. Isse said.

The World Health Organization has warned of a “second disaster” if potentially lethal, waterborne diseases like cholera spread in the devastated region. On Tuesday, it said 900,000 oral cholera vaccines were expected to arrive this week.