The hantavirus outbreak on the MV Hondius cruise ship has thrown a previously little-known virus into international headlines and mobilized health authorities from all corners of the globe, with the head of the World Health Organization arriving in Spain Sunday ahead of the ship’s arrival near the Canary Islands.

The outbreak was caused by same rare virus that killed Gene Hackman’s wife Betsy Arakawa in New Mexico last year, but the strain aboard the ship – the Andes virus – is uniquely able to transmit from human to human.

The story begins on November 27, when couple Leo and Mirjam Schilperoord, ornithologists from the Netherlands, set off on a months-long South America journey. They traveled through Chile, Uruguay and then back to Argentina in late March.

They are thought to have inhaled from the feces of long-tailed pygmy rice rats, which carry the virus, when they visited a landfill in Ushuaia, Argentina to spot a rare bird known as Darwin’s caracara.

Here is how things unfolded.