Peripheral blood lymphopenia and neutrophilia in children with severe respiratory syncytial virus disease.

It is not known why respiratory syncytial virus (RSV) is associated with prolonged sequelae in many children. Measles virus (also a paramyxovirus), acute stress in sepsis, and cardiac bypass all cause lymphopenia. Using a retrospective analysis of records of children in Bristol with RSV infections over 5 years, we found that children with RSV had lower lymphocyte counts than unstressed, stable children prior to cardiac surgery. Children who required intensive care had the lowest lymphocyte counts. Neutrophil counts were raised in RSV-infected children. These data may offer an insight into pathological mechanisms, and suggest new research avenues.