This weather pattern – drought followed by rain was similar during a mysterious outbreak of a fatal disease in the United States. In the Four Corners region, an unidentified infection caused acute respiratory failure. 52 people died. At the Centre for Disease Control in Atlanta Georgia - a world authority on communicable disease - scientist John Krebs describes how virologists worked to identify the killer as a strain of Hanta Virus. This lethal virus is carried by rodents. The specific pattern of weather had increased rodent numbers ten fold and increased the chances of humans coming into contact with the infected mammals. Are rodents key to the spread of the virus in Aztec Mexico?