The terminology of epidemics - infection, incubation, recovery - is convenient to describe the rules of this class. The models all follow the same general outline; there is always a healthy population which is nevertheless subject to infection at any time.
Infection through a single contact is the most plausible model, but one way to account for a disease which is hard to transmit would be to require a higher intensity of infection, exemplified perhaps by requiring multiple simultaneous contacts before infection occurs.
Once infection has occurred, nature must take its course. The model followed in this submenu supposes that a cell, once infected, itself becomes infectious through the duration of its recovery. Eventually recovery occurs, this model supposes no immunity, leaving the cycle free to repeat at any moment.