Not all whooping cough is pertussis.
The reported number of pertussis cases in the U.S. has increased dramatically in recent years as a result of waning immunity, increased physician awareness, and improved diagnostic testing. Nonetheless, laboratory confirmation remains problematic, and many diagnoses are made clinically. From 2004 through 2006, outbreaks of pertussis-like illnesses were reported in New Hampshire, Massachusetts, and Tennessee. Although all three outbreaks initially were thought to be caused by pertussis, subsequent laboratory investigation failed to confirm the diagnosis.
Each outbreak began with an index case with credible evidence for clinical pertussis (1 laboratory worker with paroxysmal coughing and posttussive emesis and 2 unimmunized infants). The index…