Story highlights There have been 1,634 deaths from the illness since April 27, the organization says

"The biggest challenge is reaching people," a WHO spokesman says

(CNN) The death toll continues to rise in Yemen, where a cholera outbreak has been spreading for months, according to the World Health Organization.

There have been 275,987 suspected cholera cases and 1,634 deaths from the illness between April 27 and July 5, the WHO said in a statement Wednesday. Children under the age of 15 make up 41% of these cases, and people older than 60 account for 33% of the deaths.

"If you get caught early in the morning with this and you don't get treated by the end of the day, then you really have a problem," WHO spokesman Christian Lindmeier said. "A weak elderly person could really be dead by the end of the day."

Cholera patients await treatment at a hospital in Sana'a, Yemen, in May.

The WHO said in a statement last week, "we are now facing the worst cholera outbreak in the world."

Cholera is caused by ingestion of Vibrio cholerae bacteria, which are spread through water or food that is contaminated with feces. Eighty percent of people with cholera don't have symptoms, but they are still capable of spreading it. Those who do show symptoms have a sudden onset of watery diarrhea, which can lead to death by severe dehydration. About 14.5 million people in Yemen don't have access to clean water and sanitation, according to the WHO.

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