Objective To investigate the relationship between tissue tropism of influenza viruses and sialic acid receptors in ferret. MethodsThe distribution of influenza viruses H5N1 (SZ406H, A/VN/1203/04), SH1N1, H3N2(Brisbane/09, HK/09) in infected ferrets was analyzed by virus isolation, and the distribution of sialic acid receptors in tissues was determined by direct immunofluorescence assay. The binding of influenza virus to sialic acid receptor was detected by indirect immunofluorescence assay. ResultsH5N1 (SZ) and H5N1 (A/VN/1203/04) viruses were detected in the liver, spleen, lung and intestine. In addition, H5N1(A/VN/1203/04) virus was also detected in the brain. SH1N1 and H3N2(Brisbane/09, HK/09) viruses were detected in the intestine. Sialic acid receptors type I SAα2,6Gal and SAα2,3Gal were distributed in the spleen, heart, lung, intestine, and brain, type II SAα2,3Gal receptors were distributed in the spleen, heart, lung, intestine, brain, and liver. SH1N1 virus was bound to SAα2,6Gal in the tissues, while H5N1 was bound to SAα2,3Gal. ConclusionsOur results indicate that H5N1(SZ,VN) virus can be distributed in many organs in ferret. SH1N1 and H3N2(HK,BR) viruses are only distributed in the intestine, while both SAα2,3Gal and SAα2,6 Gal receptors are distributed in many organs. So that we would conclude that SA receptors are not determinant factors for organ distribution of different subtype influenza viruses in ferrets. 