MEXICO CITY — Venezuela’s refugee crisis is the worst Latin America has ever experienced. In the past 15 years, more than five million Venezuelans, equivalent to 16 percent of the population, have left their country. By the end of this year, six million Venezuelans will have fled their country. Only the civil war in El Salvador, a much smaller country, in the 1980s displaced a similar proportion of citizens.

Although the diaspora is far-flung, stretching from Spain to Chile, Colombia has borne a disproportionate share of the heavy burden of the influx. One of Venezuela’s three continental neighbors, it has taken in the largest cohort of refugees fleeing Nicolás Maduro’s dictatorship. In comparison, the United States will accept only 18,000 refugees, from all over the world, this fiscal year.

Colombia began giving protection to refugees under its previous government, led by Juan Manuel Santos, who won the Nobel Peace Prize for pursuing a peace agreement with the guerrilla rebels of the Revolutionary Armed Forces of Colombia, or FARC. The country’s policy of open borders as well as extending health care and protection to Venezuelans continued under his successor Iván Duque, a right-of-center technocrat, who, at first glance, would not be an obvious candidate for expressing such solidarity with poor Venezuelans — especially since many of his compatriots are less sympathetic to their plight.

The refugees pouring across the border into Cúcuta are largely destitute: men, women and children fleeing not only repression and human rights violations carried out by Mr. Maduro, but more significantly, hunger, disease and a lack of basic necessities including medicine. They are running from a crisis that has dragged on for years with no end in sight.