Detection of influenza virus RNA in peripheral blood mononuclear cells of influenza patients

Gastroenteritis, arthralgaia and myalgia are frequently associated with influenza virus infections in humans. One explanation for these symptoms may be extrarespiratory transmission of virus by peripheral blood mononuclear cells (PBMC). We tried to detect genomic viral RNA of the nucleoprotein (NP) and H3 subtype hemagglutinin (HA) genes by the method of RT-PCR in PBMC of 18 children aged 1-14 who sufferred from an influenza outbreak in the Kansai district of Japan between December 1992 and February 1993. Three of the 18 samples were RT-PCR positive. The NP gene sequence observed in one patient's PBMC was identical to that obtained from his throat swab fluid. The HA gene sequences observed in the two other PBMC differed from those of RT-PCR-amplified DNA from throat swabs by an order of 3-9 nucleotides. We believe these results suggest the presence of a PBMC-associated virus.