Pertussis and respiratory syncytial virus infections.

During the winter 2005-2006, all infants <4 months of age admitted for bronchiolitis or acute respiratory tract infection in a tertiary care pediatric hospital in Paris were tested for respiratory syncytial virus (RSV) and pertussis with real-time polymerase-chain reaction (RT-PCR). A positive pertussis-PCR was found in 14/90 (16%) infants infected with RSV and in 5/30 negative for RSV. Similar clinical symptoms were found in all RSV-positive infants with or without pertussis co-infection. Most infants (73%) were not vaccinated against pertussis, and the other children had received one or two injections. In conclusion, pertussis-RSV co-infection is common in young infants, and pertussis-PCR should be used, whenever available.