April 2: Patient Zero in Tijuana, Mexico eats the infected mushrooms, thus beginning the pandemic.
April 3: 14 more eat the infected mushrooms, and these are all over the world. If not for the global nature of the beginning, the plague may have not gotten to driving humanity on the brink of extinction. These 21 are spread out in the following locations: Los Angeles, Mexico City, Boston, Seattle, Atlanta, New York, Toronto, Pretoria, Orlando, Miami, Houston, Rio De Janeiro, London, Bejing, Shanghai, Mumbai, Monrovia, Istanbul, Pyongyang, Seoul, and Tokyo.
The first case of human-to-human transmission, Patient Zero crosses the border into the US, 29 hours after eating the infected mushrooms. He turns while waiting in line, and gets out and infects 5 U.S Customs officials, 3 Mexican customs officials, and 4 pedestrians.
A map of the first CBI cases - zoom out to get the full map
April 4: 6 more people are infected, this time all 6 are in South America.