Infectious agents - normal flora become pathogenic
Reservoir - anyplace where pathogens can live, they multiply
3. Portal of exit - body fluids, coughing, seeping wounds, IV lines..
4. Mode of transmission - contact, droplet, airborne, vector
5. Portal of entry - eyes nares, mouth, urethra, vagina, wounds, IV or drainage sites.
6. Susceptible host - person w. inadequate defense. Elderly, really young, immune deficiency.