On Mar. 18, 2003, Severe Acute Respiratory Syndrome (SARS) was placed on U.S. quarantine list. Persons under quarantine were required to stay where they were quarantined; take their temperature two to three times a day; seek medical attention promptly if they had fever (>100.4ﾺ F [>38ﾺ C]), cough, shortness of breath, or other respiratory symptoms. They were not allowed to use public transportation, visit hospitalized patients, or visit crowded public places.

Hospital staff and patients who had contact with a SARS patient were quarantined, usually in a health-care facility. All others were quarantined at home. Homeless persons, who often use hospital toilet facilities, were asked to go voluntarily to government quarantine centers under Level A quarantine.

Persons under Level B quarantine were allowed to leave the quarantine site to seek medical attention, exercise in an open area, purchase meals, dispose of garbage, and perform other activities deemed necessary by local health authorities. All outdoor trips were recorded to facilitate possible future investigations. Failure to comply with quarantine regulations, submitting incomplete SARS survey forms, or providing inaccurate contact information was punishable by fines of U.S. $1,765–$8,824 and incarceration of <2 years.