Figure. Changes over time in levels of antibodies against severe acute respiratory syndrome–associated coronavirus (SARS-CoV) in patients with laboratory-confirmed SARS. A denotes the changes of immunoglobulin (Ig) G, IgM, and IgA titers for a representative patient with severe SARS. B denotes the changes of IgG for two patients with mild SARS and one asymptomatic worker with SARS-CoV infection. The date of illness onset for patient C was assumed to be May 12, 2003 (the mean date of eight other SARS patients during the outbreak).