Immune cells could be a target of the virus infection. Previous findings showed that viral sequences and antigens have been detected in lymphocytes in lymph node tissue, as well as in Hofbauer cells (macrophages of the placenta), Kupffer cells (macrophages of the liver), and mononuclear cells in the intestinal mucosa [27] . This is consistent with our find. Our presented evidence shows that virus can be detected in macrophage. Moreover, our finding showed that viral RNA can be detected in CD3+ T lymphocytes, progenitor cells and follicular dendritic cells of spleen. The spleen is a complex organ with several functions, including the removal of senescent or aberrant red blood cells from circulation, as well as the removal of circulating pathogenic organisms [47] . So circulationg immune cell with H5N1 virus could play a role in dissemination of virus when those cells with virus can not remove the virus in cells completely. We unprecedentedly investigated 24 autopsy tissues of 5 organ systems from a dead patient of H5N1 infection. Our study results indicate that the H5N1 virus could be found in multiple organs. Viral load in infected tissues is correlated with host response. And circulating immune cell can not be excluded to play a role in dissemination of virus in vivo.