Your body is now releasing cells to fight this unknown disease you have.
Helper T Lymphocyte
Second Line of Defense
Memory B Lymphocyte
Killer T Lymphocyte
Third Line of Defense
Patient Zero's body is in the process of inflammation and lots of antibodies are being released to help fight the virus.
The Helper T Lymphocyte, marks all of the pathogens so then once the Memory T Lymphocyte comes around, it would remember that cell. The Killer T Lymphocyte would come and attack the marked and scanned pathogens.
Phagocytes will kill the left over pathogens that were marked with a certain antigen.