In 1987, thousands of people gathered in Saudi Arabia for the annual Hajj pilgrimage. But what started out as a celebration led to a worldwide health crisis: more than 2,000 cases of meningitis broke out, spreading across Saudi Arabia and the rest of the world. How did it spread so quickly and what makes meningitis so dangerous? Melvin Sanicas examines how the disease affects our bodies. Lesson by Melvin Sanicas, directed by CUB Animation Studio.