Due to the country's civil war, more than 80 percent of the population lacks food, fuel, clean water and access to healthcare.
Only 5 percent of Puerto Ricans have electricity and less than half have clean drinking water.
The WHO sent a team of experts to Congo this month to try and stop the disease's spread.
The epidemic is the most explosive on record in terms of its rapid spread.
The disease is spread by ingesting fecal matter.
The situation is spiraling out of control, says the International Committee of the Red Cross.
The outbreak in Sanaa is the second in less than a year in the war-torn country.
Health officials declared a state of emergency in Yemen's capital.
People are sheltering from conflict wherever they can, including a network of islands in the swamps.