Staphylococcus aureus is a bacterium first described in 1880 in pus from surgical abscesses. Frequently, S. aureus lives on the skin, in the nose, throat, and other body surfaces. It has been estimated that up to 30% of the population are “staph carriers,” exhibiting no symptoms unless an active infection is present. Through the 1950s, S. aureus infections were generally treated with early beta-lactam antibiotics includ- ing penicillin. In the early 1960s an antibiotic-resistant form of S. aureus, named MRSA (Methicillin- Resistant S. aureus) was isolated in the United Kingdom. MRSA was identified in the U.S. in 1968. Ini- tially described in hospitals and facilities, this strain was referred to as “health care-associated” MRSA (HA-MRSA). HA-MRSA strains had evolved an ability to resist treatment with all beta-lactam antibiot- ics, requiring treatment with specialized antibiotics. In hospitals, patients with open wounds, invasive de- vices, and compromised immune systems were at greater risk for contracting this infection. The spread of bacterial colonies from patient to patient was attributed in part to contacts with hospital staff, which sug- gests that modeling the nature and frequency of contacts between workers and patients is of central im- portance in modeling HA-MRSA transmission.