Next year, the number of Venezuelans fleeing their country will overtake the Syrian exodus. To date, more than 4 million have left. One-third of these refugees and migrants are sheltering in Colombia, which has maintained a very generous open-door policy.

However, the strain is beginning to show. We were recently in Colombia, where a senior international official told us, "Colombia is a now a ticking time bomb."

This description may be hyperbole, but the country indeed appears headed towards a tipping point. Such an outcome would exacerbate the regional humanitarian crisis triggered by Venezuela's collapse.

It could also threaten the long-term investment made by the United States in Colombia's prosperity. All this should prompt the United States and others to act now before it's too late. Six trends explain why:

The crisis in Venezuela shows no signs of abating

The political situation in Venezuela continues to deteriorate. In September, Norwegian-sponsored negotiations between the Maduro government and the opposition led by Juan Guaidó were declared dead. The economy is in freefall. Officially, there are 1.4 million Venezuelans already in Colombia, but the real figure is likely between 1.6 and 2 million. This outflow of Venezuelans will likely double in the coming year. At this rate, Venezuelans could shortly make up a tenth of Colombia's population.

Those fleeing are increasingly vulnerable.

Unlike early arrivals, Venezuelans streaming into Colombia today arrive with little more than the shirt on their backs. Many are malnourished. So are most babies born to Venezuelan women who make it to Colombia. Many have chronic illnesses like diabetes, cancer, or HIV for which they cannot be treated at home. Trafficking in women and girls and child labor are also on the rise.

All this puts heavy pressure on parts of Colombia's health-care system. The Erasmo Meoz public hospital in the border town of Cúcuta has delivered free emergency care to about 13,000 Venezuelans so far this year, but the government has failed to reimburse the hospital for those expenses. Nor can the hospital's 600 beds accommodate all who need care. Some patients lay in beds under a tarp in the heat of the parking lot.

Other host countries in the region are shutting their doors

Colombia has welcomed Venezuelans. Many have received special two-year permits that give them the right to work and access to some services. Colombia is a transit route to other host countries. But two, Peru and Ecuador, have begun to close their doors, trapping Venezuelans in Colombia. Some have been unable to join family members who passed through earlier. One humanitarian worker described these closures as acting like a cork stuck in the bottle. The pressure is building.

Donors have yet to step up

Distressingly, international donors have ponied up less than 2 percent of aid for Venezuelans they had provided at the same point for the Syrian response. A donor conference in Brussels in late October offers donors an opportunity to step up, but no one is counting on increased generosity.

Colombia's own internal crisis is heating up

In 2016, Colombia signed a peace agreement with the FARC, formally ending more than 50 years of conflict with the country's largest guerrilla group. The war had killed almost 220,000 and displaced nearly 8 million. But the peace agreement did not include Colombia's other armed groups, who continued to operate.

And now, even that accord is fraying. Several of its provisions remain unfulfilled and international support has dried up. Most worryingly, some prominent former members of the FARC announced in August that they would return to the battlefield. If others heed their call to arms, the humanitarian and security situation is likely to deteriorate rapidly.

The two crises are colliding

Fleeing Venezuelans and Colombian IDPs increasingly find themselves living on top of each other in the same marginal communities from the border to Bogota. In these areas, the Colombian state is largely absent and armed groups have filled the vacuum. Now, they are taking advantage of vulnerable Venezuelans moving into and through the territories they control 3- demanding bribes for passage, recruiting them into their ranks, and using this to fuel the drug trade.

None of this bodes well. Millions of displaced Venezuelans and Colombians are increasingly desperate. Colombia could decide to close its borders. Even if Venezuela's political and economic crisis were magically resolved tomorrow, it would take years before Venezuelans could return home.

So what is to be done?

An obvious place to begin would be to increase humanitarian aid. The United States has earmarked $160 million for Venezuelans in Colombia this year. However, the European Union and other traditional donors need to step up. The EU has spent some $6 billion to help Turkey care for 3.6 million Syrians. Last month, it pledged $33 million to Colombia. This disparity boggles the mind.

Second, for long-term success, Venezuelans should be socially and economically integrated into Colombian society. In recent years, the World Bank and the Inter-American Development Bank have introduced new finance mechanisms for middle-income countries to strengthen services and create jobs for refugees and host communities alike. They have already begun such work in Colombia, but these investments must be brought to scale.

Third, other large host countries need to reopen their doors. Peru, Ecuador, and Chile should reverse course, eliminating unrealistic visa requirements for Venezuelans. In exchange, the World Bank and others could fast-track concessional financing to Peru and Ecuador to help those governments foot the bill.

Fourth, the United States should grant Temporary Protected Status (TPS) for Venezuelans. The TPS program prevents foreign nationals from being deported to countries where they would be at risk. The Trump administration has so far refused to extend the program to Venezuelans despite bipartisan support among lawmakers. Congress should act where the administration has failed to do so.

Hardin Lang is the vice president for programs and policy at Refugees International. Natacha Weiss is co-chairperson of the board of directors of Refugees International and previously worked as an advocate for the organization from 1995 to 2000.