Whooping Cough: An Unwelcome Return

Between 1920 and 1950, 200,000 Americans, on average, developed whooping cough (pertussis), an incessant dry cough, each year. Whooping cough is caused by the gram-negative bacterium Bordetella pertussis¹ and a related species, Bordetella parapertussis.^2,3 This infection’s impact has been reduced through 60 years of aggressive immunization.¹ However, the World Health Organization indicates that in the past few years, more than 16 million cases (and roughly 200,000 deaths) have been reported worldwide,^4,5 with 30,000 to 40,000 deaths reported annually in the United States between 2010 and 2014.6 Infants are at greatest risk for hospitalization and death.⁷ Whooping cough is back.

B pertussis causes respiratory tract inflammation and increased mucus production. In response, patients cough frequently, sometimes relentlessly. Eventually, they experience intractable bouts of coughing and alarming spasms during which the windpipe closes, leaving them temporarily unable to breathe. Once they are able to breathe again, patients make an involuntary “whoop”— the noise from which the infection derives its common name—as inspired air goes through a still partially closed airway.⁸

Most cases of pertussis occur in developing countries. However, in developed countries—including the United States— the number of cases tripled between 2010 and 2012 compared with previous years.¹ The incidence of pertussis in the United States is cyclic, with peaks every 3 to 5 years as the number of susceptible persons in the population increases.⁷ This increase in cases has public health officials concerned and experts investigating possible causes (Table 1^9-12).

Symptoms

Although the typical incubation period for pertussis is 9 to 10 days, it can range from 6 to 20 days. After the incubation period, inflammation and excess mucous production begin.¹³ At first, symptoms (called the catarrhal stage) resemble those of the common cold: mild cough, low-grade fever, and a stuffy or runny nose. The characteristic “whoop” may also appear, although elderly adults and infants sometimes do not develop this symptom but are at elevated risk for apneic exhaustion. The severe paroxysmal cough that can last for up to 6 weeks can cause dehydration, difficulty breathing and sleeping, and vomiting. Once this severe coughing ends, a milder cough will continue for an additional 7 to 10 days.¹⁴

Complications can include ear infection, appetite loss, coughing blood, dehydration, and hernia. Infants and younger children may also develop irregular breathing, seizures, and/or pneumonia. Children younger than 1 year experience the most severe symptoms and may require hospitalization. In adults, the severe coughs can lead to involuntary urination, dizziness, and/or fractured ribs.¹⁴

Prevention

The DTaP (diphtheria, tetanus, and pertussis) vaccine has helped to limit the number of pertussis cases. However, the vaccine’s effectiveness appears to wane over time. The Centers for Disease Control and Prevention (CDC) recommends children receive DTaP in 5 doses before age 6 years (Online Table 2⁴). Five years after the last dose is administered, its effectiveness falls to 70%, necessitating a booster shot for adolescents.

Table 2: CDC Recommendation for Acellular Pertussis Vaccine (DTaP) in Children

Dose

Age

First

2 months

Second

4 months

Third

6 months

Fourth

15-18 months

Fifth

4-6 years

^{Adapted from reference 4.}

Adults (individuals older than 18 years) who have not received the DTaP series should receive 1 dose of Tdap (tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis vaccine). Tdap resembles DTaP, but is recommended for individuals aged 11 to 64 years.⁴ Tdap is recommended especially for adults who will come into contact with a newborn within 2 weeks after the infant receives the booster or if there has been a pertussis outbreak. When newborns are immunized against pertussis, all people who come into contact with them, especially adults whose protection may have waned, should be up-to-date with their immunizations.⁴

In addition, all pregnant women should be vaccinated with Tdap even if they were previously vaccinated. If, however, a woman is not vaccinated with Tdap during her pregnancy, she should be immunized immediately postpartum.¹⁵

Treatment

Health care providers typically diagnose pertussis based on the symptoms and can test mucous for pertussis bacteria. They also should start treatment if they suspect pertussis, rather than waiting for test results, and should monitor the CDC’s treatment recommendations (see www .cdc.gov/pertussis/clinical/treatment. html) with regard to each patient’s unique presentation (eg, very young age, pregnancy, allergies, QTc prolongation).¹⁴

Most patients older than 1 year can be treated at home, but should be monitored and reevaluated frequently. Supportive care should be tailored to each patient’s needs and may include oxygenation, breathing treatments, and mechanical ventilation. Intractable nausea and vomiting, failure to thrive, seizures, encephalopathy, and sustained hypoxemia during coughing paroxysms are red flags requiring hospitalization.¹⁴

Pertussis treatment should ideally begin within the first 2 weeks. Infected individuals should receive a macrolide antibiotic (erythromycin 50 mg/kg/day divided in 4 doses/day for 14 days). Cotrimoxazole is an alternative. Infected individuals remain contagious for up to 5 days after antibiotics are initiated. People who have been exposed should also be treated.16 Corticosteroids, beta2-adrenergic agonists, pertussis-specific immunoglobulin, antihistamines, and (possibly) leukotriene-receptor antagonists are not recommended.¹⁷

End Note

Increasingly, it looks like booster vaccinations may be needed for the entire adult population. Experts suggest that a single vaccination strategy is unlikely to eliminate circulating B pertussis or to completely protect infants against severe disease. Multiple immunization strategies with current vaccines are being studied.¹² The goal is to consign whooping cough to the history books once and for all.

Ms. Wick is a visiting professor at the University of Connecticut School of Pharmacy and a certified immunizer.

References

• Rumbo M, Hozbor D. Development of improved pertussis vaccine. Hum Vaccin Immunother. 2014;10(8):2450-2453. doi: 10.4161/hv.29253.
• Cherry JD, Seaton BL. Patterns of Bordetella parapertussis respiratory illnesses: 2008-2010. Clin Infect Dis. 2012;54(4):534-537. doi: 10.1093/cid/cir860.
• David S, van Furth R, Mooi FR. Efficacies of whole cell and acellular pertussis vaccines against Bordetella parapertussis in a mouse model. Vaccine. 2004;22(15-16):1892-1898
• Pertussis vaccines: WHO position paper. Wkly Epidemiol Rec. 2010;85(40):385-400.
• Mimms S. As the number of unvaccinated Americans grows, measles and whooping cough make a comeback. Nationaljournal.com. 3 June 2014.
• National Center for Immunization and Respiratory Diseases, Division of Bacterial Diseases. Pertussis cases by year (1922-2014). Centers for Disease Control and Prevention website. www.cdc.gov/pertussis/surv-reporting/cases-by-year.html. Updated March 6, 2015. Accessed August 11, 2015.
• del Portal DA, Karras DJ. Infectious disease/CDC update. Update on emerging infections: news from the Centers for Disease Control and Prevention. Ann Emerg Med. 2013;62(1):91-93. doi: 10.1016/j.annemergmed.2013.04.001.
• Tefon BE, Özcengiz E, Özcengiz G. Pertussis vaccines: state-of-the-art and future trends. Curr Top Med Chem. 2013;13(20):2581-2596.
• Wendelboe AM, Van Rie A, Salmaso S, Englund JA. Duration of immunity against pertussis after natural infection or vaccination. Pediatr Infect Dis J. 2005;24(suppl 5):S58-S61.
• Mooi FR, van Loo IH, King AJ. Adaptation of Bordetella pertussis to vaccination: a cause for its reemergence? Emerg Infect Dis. 2001;7(suppl 3):526-528.
• Warfel JM, Zimmerman LI, Merkel TJ. Acellular pertussis vaccines protect against disease but fail to prevent infection and transmission in a nonhuman primate model. Proc Natl Acad Sci USA. 2014;111(2):787-792. doi: 10.1073/pnas.1314688110.
• Gaillard ME, Bottero D, Moreno G, Rumbo M, Hozbor D. Strategies and new developments to control pertussis, an actual health problem. Pathog Dis. 2015. pii: ftv059. Epub ahead of print]
• Immunization, vaccines and biologicals: pertussis. World Health Organization website. www.who.int/immunization/topics/pertussis/en/. Updated June 21, 2011. Accessed August 10, 2015.
• Treatment. Centers for Disease Control and Prevention website. www.cdc.gov/pertussis/clinical/treatment.html. Updated March 20, 2013. Accessed August 10, 2015.
• CDC Advisory Committee for Immunization Practices recommends Tdap immunization for pregnant women [news release]. Atlanta, GA: Centers for Disease Control and Prevention; October 24, 2012. www.cdc.gov/media/releases/2012/a1024_Tdap_immunization.html. Accessed August 10, 2015.
• Bocka JJ, Steele RW. Pertussis medication. Medscape website. http://emedicine.medscape.com/article/967268-medication. Updated December 5, 2014. Accessed August 10, 2015.
• Bettiol S, Thompson MJ, Roberts NW, Perera R, Heneghan CJ, Harnden A. Symptomatic treatment of the cough in whooping cough. Cochrane Database Syst Rev. 2010;(1):CD003257. doi: 10.1002/14651858.CD003257.pub3.