Whooping Cough (Pertussis): Symptoms, Complications, and Prevention
Also known as: Pertussis
What is whooping cough?
Whooping cough, also called pertussis, is a highly contagious bacterial respiratory infection caused by Bordetella pertussis. It causes serious illness in people of all ages, but it is most dangerous for babies. In the United States, whooping cough returns in cyclical outbreaks every 3 to 5 years despite vaccination, in large part because protection from the vaccine fades over the years.
That waning protection is well documented. After the full childhood DTaP series, effectiveness drops from about 98% in the first year to roughly 71% five years later. In adolescents, effectiveness falls from about 73% within a year of the booster to about 34% after two to four years.
Causes and risk factors
Whooping cough spreads through the air, in droplets released when an infected person coughs or sneezes, and through close breathing contact. It spreads easily within households, which is why one case in a family often becomes several.
Babies under 6 months old, who are unvaccinated or only partly vaccinated, face the highest risk of severe disease. Adults whose immunity has faded can carry the infection with only a nagging cough and pass it to a newborn without ever realizing it.
Symptoms
The illness moves through three stages, each typically lasting 1 to 2 weeks, though the stages often run longer in teenagers and adults:
- An early cold-like phase: runny nose, mild fever, and an occasional cough
- A coughing phase: violent, repeated bursts of coughing, sometimes followed by a loud gasp for air (the classic “whoop”), often with vomiting and exhaustion afterward
- A recovery phase: the fits slowly become less frequent
In babies, the cough may be mild or absent altogether, replaced by choking spells and long pauses in breathing (apnea), sometimes with a bluish color. Apnea is a medical emergency. Coughing fits can also come back months later with the next respiratory infection.
Complications
Complications are concentrated in the youngest patients. About half of babies under 1 year old who get whooping cough need to be cared for in the hospital, where treatment may include humidified oxygen and intravenous fluids when coughing prevents them from drinking. The complications that drive those admissions in young infants are apnea, low blood oxygen, dehydration, and pneumonia.
Diagnosis
Diagnosis starts with the clinical picture, prolonged coughing fits and a known exposure, and is confirmed in the lab. A PCR test on a nasopharyngeal swab is the main confirmatory test, and performs best when done within 1 to 4 weeks of the first symptoms. A blood count can help too: in babies under 3 months, a white cell count above 20,000/µL with more than 50% lymphocytes strongly suggests pertussis. A chest x-ray is sometimes added.
Treatment
- Antibiotics (usually macrolides such as erythromycin) work best when started early. They are still recommended for up to 3 weeks after the cough begins, mainly to stop the spread. Started later than that, they rarely change the course of the illness, because the damage is already done.
- Hospital care for babies with severe disease, especially those under 6 months, given the risk of apnea, low oxygen, dehydration, and pneumonia
- Supportive care: fluids, smaller and more frequent meals, and close monitoring of breathing
- Staying home from school, daycare, or work until 5 days of antibiotics are complete. Untreated, a person can stay contagious for up to 3 weeks after the cough starts.
- Preventive antibiotics for household members and other close contacts at high risk, most effective when started within 21 days of the first cough
Prevention
Vaccination is the core of prevention. Children get the DTaP vaccine at 2, 4, 6, and 15 to 18 months, with a booster at 4 to 6 years. A Tdap booster follows at age 11 or 12, and adults who never received one should get a dose, then a booster every 10 years.
The single most effective step for protecting a newborn is vaccinating the mother: a Tdap dose during every pregnancy, between 27 and 36 weeks of gestation, passes antibodies across the placenta and shields the baby during the window before their own shots begin. Vaccinating the people who will be around the baby is a useful complement, and anyone in close contact with an infant under 12 months should be up to date on Tdap. On its own, though, vaccinating the entourage is no longer relied on as the main strategy, since vaccinated people can still catch and pass on pertussis.
When should you see a doctor?
See a doctor promptly for coughing fits that drag on, particularly in a baby. Seek emergency care if an infant has pauses in breathing, turns blue, or is struggling to breathe.
Sources
- MedlinePlus, U.S. National Library of Medicine health information
- MedlinePlus Medical Encyclopedia: Whooping cough, symptoms, treatment, and vaccination
- StatPearls, NCBI Bookshelf (National Library of Medicine), clinical review of pertussis
- American Lung Association, patient education and resources