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Pertussis (Whooping Cough): An Under Recognized Disease in Adults

Barry A. Mizock MD, FACP, FCCCM
- Senior Physician and Associate Director of the Medical Intensive Care Unit at the John Stroger Hospital

Pertussis (whooping cough) is generally promptly recognized in infants and children. However, the diagnosis of pertussis is often missed or delayed in adolescents and adults where the symptoms are commonly ascribed to a viral upper respiratory infection. The incidence of pediatric pertussis has been markedly reduced since routine vaccination of children was instituted in the 1950’s. However, during the past two decades the overall incidence of the disease has increased, due in large part to new cases in adults and adolescents who were previously immunized (immunity against pertussis dwindles 4-12 years after vaccination).

The clinical manifestations of pertussis have been divided into three stages: an initial (catarrhal) stage, lasting 1-2 weeks, characterized by cold-like symptoms (e.g. low-grade fever, muscle aches, runny nose, watery eyes). This is followed by a second (paroxysmal) phase in which symptoms of an acute bronchitis dominate the picture. Pertussis-associated bronchitis is characterized by violent, repetitive, uncontrolled, coughing “spasms” (paroxysms) that may be associated with vomiting, or loss of consciousness. Wheezing may also occur. The characteristic inspiratory “whoop” seen in children is much less common in adults. The paroxysmal phase may last from 1-6 weeks, and often results in the patient seeking medical care in a physician’s office or emergency room. The third (convalescent) phase lasts 2-12 weeks during which time symptoms gradually improve. It has been estimated that 20-25% of adults with prolonged cough (lasting less than 3 weeks) have laboratory evidence of recent pertussis infection.

Clinical diagnosis of pertussis is made by the presence of an acute cough for 14 days plus either paroxysmal cough, vomiting following coughing, or inspiratory “whooping”. The chest x-ray is most often normal but may show patchy abnormalities. The diagnosis of pertussis can be confirmed by growing the organism in culture, or by more sophisticated testing (e.g., PCR assay).

Definitive treatment of pertussis with antibiotics should be initiated based on a characteristic clinical presentation without waiting for laboratory confirmation. Oral erythromycin for 14 days was previously considered the treatment of choice, but has now been supplanted by azithromycin (x 5 days), or clarithromycin (x 7d) due to better patient compliance. Antibiotics have not been shown to reduce disease duration once paroxysmal coughing has begun. However, antibiotic therapy at this stage serves to reduce transmission to individuals at risk (e.g., infants, children). The disease is highly infectious (it is spread by aerosolized droplets from coughing or sneezing). Patients are considered contagious until 3 weeks after the end of the paroxysmal stage, or until after 5 days of antibiotics. Close household contacts should receive prophylactic antibiotics, even if they are asymptomatic. Supportive therapy of pertussis involves administration of drugs that reduce symptoms such as antihistamines, corticosteroids, bronchodilators. Routine administration of these drugs is not recommended, but they may provide symptomatic relief in selected cases.

New standards for vaccination for pertussis in adolescents and adults have been recently proposed in 2006 by the Advisory Committee on Immunization Practices to the CDC (http://www.cdc.gov/nip/publications/VIS/vis-dtp.pdf).They recommend administration of a single dose of the tetanus diphtheria acellular pertussis vaccine (Tdap) (e.g. Adacel) for adults age 19 to 64 years to replace a single booster dose of tetanus diphtheria (Td) vaccine (generally given if >10yrs have elapsed since the last vaccination). Health care workers who are in direct patient contact should also be vaccinated with Tdap. In addition, adults who are likely to have close contact with infants less than 1 yr of age should also receive the vaccine, at least 1 month prior to contact. The Tdap vaccine is not recommended to adults older than 65 years. However, these individuals still require a tetanus-diphtheria booster every 10 years.