Detection of influenza B virus in throat swabs using the polymerase chain reaction.

: An assay protocol based on exploiting the polymerase chain reaction (PCR) for the direct detection of influenza B virus in throat swabs is described. By the use of PCR with nested primers, it was possible to detect the virus in throat swabs. Dilution experiments showed that as little as 1 plaque forming unit of virus was sufficient for detecting the HA gene by the PCR. All throat swab samples from which influenza B virus had been isolated by conventional methods were also positive by the PCR method.