Learn English: How Viruses Had to Overcome Huge Odds to Spread Across Oceans (hard)

Before airplanes and fast ships, illnesses often died out on board before reaching land, a new study reveals.

Researchers used mathematical models to show that viruses had a very low chance of crossing the ocean.

This is because most illnesses would naturally disappear within the confined space of a ship.

The study suggests that viral transmission became significantly easier with the advent of modern transportation.