A full timeline of canon and the game is located in the group, but here is an abbreviated one:
June 13 - the virus breaches containment and begins to spread.
June 21 - a majority of the population of the town patient zero crashed into on the 16 are dead and there are outbreaks across the entire country.
June 24 - The virus is considered out of control in 30 cities and 12 states.
June 26 - A clearly ill president of the United States denies the severity of the flu and the rumor it was government made - being sure to also note the worldwide outbreaks.
June 27 - A majority of the population is dead or nearly so.