(CNN) It's not just the fear of deportation that migrants face while crossing the Mexican border to the US. It's the possibility of a slow, agonizing death while crossing a scorching desert or being crammed between 100 other people in an overheated semi truck.

So what drives these people to take such drastic risks? While some undocumented immigrants crossing the Mexico-US border are indeed Mexican, many embark on much longer journeys -- from Central America and beyond.

Here's a snapshot of the conditions in some of the countries they're fleeing:

Honduras

Police hold a boy whose father was killed in 2016 by alleged gang members for refusing to pay them a "war tax" in Tegucigalpa, Honduras.

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