PARIS — More migrants have died or disappeared in 2016 than in any previous recorded year, more than half of them in the Mediterranean Sea.

In a survey of migration routes across the world, the International Organization for Migration reported Thursday that 7,189 migrants and refugees have died so far this year. Of the total, 4,812 migrants were lost in the Mediterranean, amid the greatest migration crisis in Europe since 1945.

In the past two years, nearly 1.5 million migrants and refugees have poured into continental Europe, mostly from war-torn regions in Africa and the Middle East.

To maximize profits, smugglers often pack as many migrants as possible into makeshift vessels. In the event of mechanical difficulties or the bad weather common in the winter months, few of these migrants can swim.

In what remains one of the worst disasters in the migrant crisis to date, an 88-foot boat crammed with nearly 700 people sank off the coast of Italy in April 2015. Only 28 of those aboard survived.