Collapsing on sidewalks and constantly vomiting, some of the Yemeni villagers barely make it to the tiny health center where doctors spread cardboard sheets in the backyard and use trees to hang bags of IV fluids for patients.

They are part of a stream of hundreds of suspected cholera victims that continues to converge on the center from the impoverished town of Bani Haydan in Yemen’s northern Hajja province. Just hours after being infected, vomiting and diarrhea cause severe dehydration that can kill without rapid intervention.

In this photo taken on Wednesday, July 26, 2017, a girl scavenges for recyclable items at a garbage dump in a street in Sanaa, Yemen. (AP Photo/Hani Mohammed)

Yemen’s raging two-year conflict has turned the country into an incubator for lethal cholera: primitive sanitation and water systems put Yemenis at risk of drinking feces-contaminated water; wells are dirtied by runoff from rainfall on piles of garbage left uncollected for weeks; farmland is irrigated with broken sewers due to lax oversight and corruption; medical intervention is delayed due to unpaid government employees and half of the country’s health facilities are out of service.

The cholera outbreak in Haiti has killed more than 9,000 people since 2010, but Yemen has seen the largest outbreak of the disease recorded in recent memory in any country in a single year. The United Nations and international aid organizations say they are shocked at the speed and scale of the outbreak.

“It’s a cholera paradise,” said George Khoury, head of the U.N. Office for the Coordination of Humanitarian Affairs in Yemen. “It’s a recipe for disaster.”

One in every 120 Yemenis is now suspected of being sick with cholera, according to the International Committee of the Red Cross.

In this photo taken on Thursday, June 29, 2017, a man is treated for suspected cholera infection at a hospital in Sanaa, Yemen. (AP Photo/Hani Mohammed)

There have been around 2,000 deaths in the country since April 27. About 5,000 people fall sick every day and more than 450,000 more are suspected of having the disease, according to the World Health Organization.

The majority of those exposed to the bacteria known as Vibrio cholerae don’t fall sick and only 1 in 10 infected people develop signs of cholera. Cases are mostly treatable with a simple rehydration solution or IV rehydration.

The role the war has played in Yemen’s cholera outbreak can’t be overemphasized, said Adeeb al-Rassabi, Sanaa general coordinator for the Electronic Disease and Warning System, the country’s epidemic surveillance system. If not for the conflict, “we would have been able to contain cholera in no more than one month, no more, no doubt.”

In this photo taken on Saturday, July 8, 2017, workers fill bottles with water at the mineral water refilling station in Sanaa, Yemen. (AP Photo/Hani Mohammed)

Khoury acknowledged that U.N. agencies were caught by surprise at the rapid increase in the spread of the disease and missed an opportunity to control it in its early stages.

U.N. organizations and government health authorities initially thought the outbreak was over after a mild wave of the disease that started in October. A decline in new cases in February prompted a cut in funds to health centers and a relaxation among health monitors, said al-Rassabi.

But the outbreak returned with a vengeance in late April and Khoury pointed to the failure of the surveillance system designed to spot early cases as a primary reason for its return.

“This is like a fire alarm so if there is smoke and the system is not working, the fire will rage (throughout) the entire place,” he said.

Yemen’s civil war pits a Saudi-led coalition supporting the internationally recognized government against Shiite Houthi rebels. Disputes between the government and Houthis over revenues have left about a million civil servants, including 30,000 medical staffers, without salaries since September.

In this photo taken on Wednesday, July 12, 2017, a girl drinks water from a well that is suspected to be contaminated water with the bacterium Vibrio cholera, on the outskirts of Sanaa, Yemen. (AP Photo/Hani Mohammed)

Rima al-Youssefi, head of the surveillance system, defended her agency, telling The Associated Press that employees work around the clock without pay. “There is no budget ... there is a severe shortage of everything,” she said.

Her agency is just one of many state bodies that have been left to fall apart without help from the international community. Although the U.N. has appealed for $2.1 billion for relief work this year, only 44 percent has been funded.

In the town of Kohlan al-Sharaf, not far from Bani Haydan, doctors use overhead flashlights to examine patients in a school converted into a makeshift health center after the facility next door reached full capacity.

In this photo taken on Wednesday, July 26, 2017, a man fills a tank lorry with water from a water-tap in Sanaa, Yemen. (AP Photo/Hani Mohammed)

Cash-strapped doctors say they haven’t been paid for months and some have pawned their wives’ jewelry to buy clean water. Health workers tasked to monitor, collect and report data to the central agency are in debt, even borrowing money to charge their phones.

The war, which has killed 10,000 civilians, caused famine to spread to parts of the country. U.N. figures show there are 17 million people who are hungry. Nearly 80 percent of Yemen’s children need humanitarian assistance while 2.2 million children suffer from acute malnutrition. Around 14.5 million people do not have access to clean water and sanitation.

The chance of death from cholera increases if patients already suffer from malnutrition or other health issues.

Last month, U.N. agencies canceled the delivery of a million doses of vaccines, saying it was already too late for the vaccines to act as a preventive measure. Another reason was concern that their uneven distribution in areas under Houthi and government control could fuel the conflict.

The strong majority of cholera-infected people, who have access to health services, survive.

In this photo taken on Thursday, Jun. 29, 2017, an elderly woman is treated for suspected cholera infection at a hospital in Sanaa, Yemen. (AP Photo/Hani Mohammed)

U.N. agencies have set up more than 1,000 centers for treatment and are trying to compensate medical workers with stipends and help thousands of volunteers who go from door to door to spread awareness among families on how to protect themselves from cholera.

A recently updated map from WHO shows cholera has affected 22 of Yemen’s 23 provinces but is concentrated in the northern region, which falls under the Houthis’ control. This is where the majority of the population lives — about 70 percent of Yemen’s 26 million people.

According to WHO, the Hajja province northwest of Sanaa ranks among the worst stricken areas and has a total 366 deaths since the second wave of the disease started April 27. In some areas in Hajja out of reach of U.N. agencies, large numbers of Yemenis have been infected. In Bani Haydan village, nearly 20 percent of the population has fallen sick or died of cholera.

The civil war has forced the displacement of 3 million people, further contributing to the problem. When newcomers to a village set up septic tanks underneath their houses not far from water wells, sewage often leaks into the drinking water.

In the cholera hotspot of al-Umayri village, where the first case was reported in Sanaa province, one water well labeled “polluted” is still frequented by barefoot boys carrying jerry cans. Near Sanaa’s main water treatment plant, which pumps treated sewage to farmlands, farmers frequently break the pipelines and irrigate their farmlands with raw sewage. The harvest goes to Sanaa’s residents and restaurants.

In this photo taken on Wednesday, July 12, 2017, boys carry buckets to fill with water from a well that is alleged to be contaminated water with the bacterium Vibrio cholera, on the outskirts of Sanaa, Yemen. (AP Photo/Hani Mohammed)

Poor sanitation and sewage are decades-old problems in Yemen, where millions depend on water wells.

Some fall under the jurisdiction of central authorities but the majority are run by individuals who sell the water to truck owners, who then distribute it to tanks attached to households. Depending on their income, families either buy water directly extracted from wells — usually not a safe source of drinking water— or from a mushrooming number of privately owned water stations, which disinfect and purify water before selling it in bottles.

Field workers take samples from the wells and stations. Those found contaminated are ordered shut down. However, many bribe corrupt bureaucrats to get their stations or wells reopened.

In this photo taken on Wednesday, July 12, 2017, people fill buckets with water from a well that is suspected to be contaminated water with the bacterium Vibrio cholera, on the outskirts of Sanaa, Yemen. (AP Photo/Hani Mohammed)

Nashwan al-Attab, deputy health minister, produced a map of Sanaa province. Red dots depicted cases of cholera, many concentrated around water wells. “We believe they are contaminated ... there is no other explanation.”

Cholera outbreaks will continue until millions of Yemenis get access to clean water and that will remain a challenge as long as there is war, experts say.

“My main message here is that if the cholera outbreak goes down, don’t forget about Yemen and stop supporting (the country), else we may have another (outbreak) in a few months,” said Marije Broekhuijsen, a UNICEF sanitation and hygiene specialist.