2010.04.20 Quiz: Why is 2009 H1N1 Pneumonia Sometimes So Severe?

Which of the following is incorrect?
A. Human seasonal flu virus preferentially recognizes the alpha 2-6 sialic acid residue (in upper respiratory tract), while the 2009 H1N1 flu virus can bind to both alpha 2-3 (in lower respiratory tract) and alpha 2-6 sialic acid residues (in upper respiratory tract) equally well.
B. 2009 H1N1 can induce much higher levels of pro-inflammatory cytokines than seasonal flu virus
C. Seroprevalence studies showed that increasing age is associated with a higher likelihood of having cross-reative antibodies, but the level of antibodies is much lower in the Chinese population, around only 4% of those over 60 years of age.
D. Low levels of IgG₂ have been found to be associated with severe disease
E. In general, influenza patients are more prone to secondary bacterial pulmonary infection, but Staphylococcous aureus co-infection will not lead to increased viral replication