The world is witnessing a resurgence of cholera accompanying several hunger crises that threaten more than 20 million people in four countries.

Some 100,000 people are estimated to be sick with the water-borne, often fatal bacterial disease in war-torn Yemen. Cholera outbreaks have also struck Nigeria, South Sudan and Somalia in the past year. The disease tends to erupt amid famine, making a bad situation much worse.

“Cholera will come to kick you while you are down, and can spread to disastrous levels if not addressed immediately,” Michelle Gayer, emergency health director at the International Rescue Committee, warned in a statement this week.

Yemen is down. International intervention escalated a conflict between the country’s government and Houthi rebels. Civilians bear the brunt of the conflict. Access to clean water is cut off, trash piles build up in major cities and hospitals are destroyed. More than 4,600 civilians were killed the two years since fighting began and the U.N. estimates more than 18.8 million people need humanitarian assistance.

Aid groups are scrambling to stop the spread of the disease at a time when they already struggle to keep up with increasing rates of malnutrition. Nearly 7 million people are severely food insecure, says the World Food Program. It and other U.N. agencies warned in recent months that they are struggling to keep up with the increasing rates of hunger.

U.N. agencies and aid groups are responding to cholera ‘hot spots’ to stop the spread of the water-borne disease that causes and can turn deadly if untreated. Nearly 800 people in Yemen have died as a result of the current outbreak, which the WHO this week estimated has spread to 100,000 and continues to worsen.

As with nearly every humanitarian response, there is not enough money. Donors still need to contribute billions of dollars just for the famine response, let alone the millions needed to stop the spread of cholera.

“With inadequate humanitarian funding, aid agencies are not able to build up and deliver services quickly enough to address food insecurity and the cholera outbreak,” Gayer said. “This is a recipe for disaster.”

The hunger and cholera crises share the same cause – government failure and conflict. Yemen is on the “brink of famine” due to “man-made” causes, declared the U.N.’s humanitarian chief Stephen O’Brien in March. It is the same idea put forward by Nobel Prize-winning economist Amartya Sen in his renowned book Democracy as Freedom.

“No famine has ever taken place in the history of the world in a functioning democracy,” he said.

As Sen and other experts on these kinds of crises contend, famine is not really caused by lack of food or drought, but by governments that are unable to support their citizens. In the case of Yemen, food is no longer easily accessible. Insecurity prevents farmers from working their fields, trucks from transporting crops and stores from selling produce. It causes food prices to rise at a time when the economy is collapsing and unemployment is rising.

Similar issues contribute to the spread of cholera. More than half of the country does not have access to clean water. People drinking water from contaminated sources are vulnerable to diseases like cholera.

Humanitarian organizations respond to outbreaks by providing access to clean water, setting up treatment centers and dispensing oral vaccines. The concerted effort helps deal with the sudden onset of the disease by both stopping the spread and treating sick people. A hunger response involves distributing food and expanding health services for people suffering from acute malnutrition.

The responses are designed to address the immediate problems. Some projects do have a long term impact, such as installing wells and supporting farmers. But they are only small fixes to a deeper problem. Without a functioning state food prices are unstable, markets are fragmented and health systems are weak. Another drought can trigger another crisis.

Somalia is an example of the cycle. A drought in 2009 and 2010 triggered a famine that killed as many as 260,000 people. The country was dealing with the al-Shabaab insurgency that managed to prevent the government from functioning efficiently and made it harder for aid groups to provide assistance. Resilience emerged as the buzzword in the wake of the famine, serving as a rallying cry to implement programs that help people deal with future droughts.

Drought returned in 2016 and hunger once again rose in Somalia. The good news is that al-Shabaab is weaker than it was 7 years ago, but the government is still building up its basic institutions. As a result, people are left without access to basic necessities, such as food and clean water. Hunger and cholera returned as a result of those shortcomings.

The three other famine-prone countries face similar challenges. Insecurity and weak governance amplify the challenges faced by people living in poverty. It will get worse soon if nothing is done, said aid groups.

“As the rainy season is upon us, we cannot sit here idle and watch this crisis take yet another horrific turn,” Gayer said. “It is our collective responsibility to do everything to stop this outbreak in its tracks.”