Response of C-Reactive Protein and Serum Amyloid A to Influenza A Infection in Older Adults

Influenza epidemics are associated with significant morbidity and mortality in the elderly, with a substantial proportion of deaths due to cardiovascular events. Elevations of acutephase proteins have been associated with an increased risk of atherosclerotic events. Therefore, serum amyloid A (SAA) and C-reactive protein (CRP) were measured during influenza illness and 4 weeks later in 7 young persons, 15 elderly outpatients, and 36 hospitalized adults. Striking elevations were seen in mean acute SAA and CRP levels in all groups, but hospitalized patients had the highest levels (SAA, 503 vs. 310 mg/mL [ ]; CRP, 120 vs. 34 mg/mL P p .006 [ ]). The presence of dyspnea, wheezing, and fever was also associated with high CRP P ! .001 levels. Influenza infection is associated with significant elevations of SAA and CRP levels in elderly patients, especially those who require hospitalization. It is possible that direct effects of CRP may exacerbate preexisting atherosclerotic lesions and may help explain cardiovascular events associated with acute influenza. Influenza epidemics are associated with excess morbidity and mortality, with the highest hospitalization and death rates occurring among the elderly. Although many deaths are due to pneumonia, there is also a peak in deaths due to ischemic heart