A Swiss study in which only 2.5% percent of 1,049 pediatric ambulatory and hospitalized patients presenting with a cough-illness and who were tests for pertussis were culture positive for B. pertussis or parapertussis. Probably a relatively accurate picture of the general prevalance of pertussis in a non-outbreak situation. They additionally report that viral superinfection is rare enough to be coincidental – 0.6% – although the authors do note other studies have reported higher incidence, particularly in RSV+ hospitalized children <6 months of age.
So, this data is out the window if there’s an outbreak situation, but the overall clinical take home is that, yet again, our index of suspicion may be too high for an infrequently diagnosed condition – and we should moderate testing in the lower acuity cases.
“Bordetella pertussis and Concomitant Viral Respiratory Tract Infections are Rare in Children With Cough Illness.”
www.ncbi.nlm.nih.gov/pubmed/21407144