C3 and infection: Infection of guinea pigs with A/Tiger/Harbin/01/2002 (H5N1) (HAB01), 2009 pandemic H1N1 A/Changchun/01/2009 (CH01) or a mouse-adapted A/Changchun/01/2009 H1N1 variant (MA CH01) resulted in increased concentrations of C3 in the serum when compared to uninfected controls (Figure 5A).