Distribution of viral RNA, sialic acid receptor, and pathology in H5N1 avian influenza patients.

Avian influenza virus H5N1 infects and causes severe disease in humans. Despite the increasing number of fatal cases in 15 countries and the threat of influenza pandemic, detailed pathologic and virologic findings in humans are limited. In this study, we describe histopathologic findings, distributions of viral RNA and the Neu5Acα2-3Galβ1-4 sialic acid receptor in human tissues from three fatal avian influenza cases. Many of our findings are in agreement with previously published autopsy studies, that is, viral RNA and receptor were detected in type II pneumocytes, tracheal epithelium, intestinal epithelium, spleen, lymph nodes, and Kupffer's cells. In addition, we detected the viral RNA in glomeruli and renal tubules. There was a good correlation between viral RNA distribution and the presence of the sialic acid receptor. Despite the wide distribution of viral RNA, tissue damage and inflammation were mainly limited to pulmonary tissue.