Pertussis (Whooping Cough)

Overview

Pertussis, commonly called whooping cough, is a highly contagious infection of the respiratory tract caused by the bacterium Bordetella pertussis. It is best known for causing intense, uncontrollable coughing fits that can make breathing difficult and are sometimes followed by a high-pitched "whoop" as the person gasps for air.

Pertussis can affect people of any age, but it is most dangerous for infants, who may not yet be fully vaccinated and can develop serious complications. The illness is sometimes called the "100-day cough" because the cough can linger for many weeks. Vaccination has greatly reduced cases, but outbreaks still occur, particularly when immunity wanes over time.

Pertussis spreads easily within households, schools, and communities, and adults or older children with mild, cold-like symptoms can unknowingly pass it to vulnerable infants. Protecting babies, who face the highest risk of severe complications, is a central goal of pertussis prevention. This is why vaccinating pregnant women and keeping family members up to date with boosters is strongly recommended.

Symptoms

Pertussis typically progresses through stages over several weeks:

• Early stage (1-2 weeks): Symptoms resemble a common cold, with a runny nose, mild cough, low-grade fever, and watery eyes.
• Paroxysmal stage: Violent, repeated coughing fits, often ending in a whooping sound, vomiting after coughing, exhaustion, and a red or blue face during fits.
• Recovery stage: The cough gradually becomes less severe over weeks to months.

Infants may not whoop or even cough much; instead, they may have pauses in breathing (apnea), turn blue, or struggle to feed. These signs are medical emergencies.

Causes

Pertussis is caused by infection with Bordetella pertussis bacteria, which attach to the lining of the airways and release toxins that inflame and damage them. This irritation triggers the characteristic coughing fits.

The infection spreads easily from person to person through respiratory droplets released when an infected person coughs or sneezes. People are most contagious early in the illness, before the severe cough develops, which makes it easy to pass on unknowingly. Adults and older children with mild illness can unknowingly spread it to vulnerable infants.

Risk Factors

• Being an infant who is too young to be fully vaccinated
• Incomplete or waning vaccination (immunity fades over years)
• Close contact with an infected person, including in households
• Pregnancy (and unvaccinated newborns of unvaccinated mothers)
• Crowded settings such as schools and childcare

Diagnosis

Pertussis can be hard to recognize early because it resembles a cold. Doctors diagnose it using:

• History and examination: The pattern of severe coughing fits, whooping, or post-cough vomiting is suggestive.
• Nasal or throat swab: A sample tested for the bacteria, often using a sensitive method that detects bacterial DNA.
• Blood tests: Sometimes used, especially later in the illness.

Early testing is most accurate, so prompt evaluation helps confirm the diagnosis and guide treatment of contacts.

Treatment

Treatment is most effective when started early, before the severe coughing stage. It includes:

• Antibiotics: Started early, they can reduce severity and, importantly, limit spread to others. Close contacts may also be given antibiotics to prevent infection.
• Supportive care: Rest, fluids, a calm environment, and small frequent meals to avoid vomiting.
• Hospital care for infants: Young babies often need monitoring, help with breathing, and feeding support because of the risk of severe complications.

Cough medicines are generally not helpful for pertussis. Once the cough is established, antibiotics no longer shorten it but still reduce contagiousness.

Prevention

• Stay up to date with pertussis vaccines (DTaP for children, Tdap booster for adolescents and adults)
• Recommend Tdap during each pregnancy to protect newborns
• Keep infants away from people with cough illnesses
• Practice good cough hygiene and handwashing
• Seek prompt antibiotic treatment to limit spread when pertussis is diagnosed in a household

When to See a Doctor

See a doctor for a prolonged or worsening cough, coughing fits, or a whooping sound, especially after known exposure. Call emergency services immediately if an infant or anyone:

• Stops breathing, has pauses in breathing, or turns blue
• Struggles to breathe or breathes very fast
• Cannot keep fluids down or shows signs of dehydration
• Has a fever with severe coughing or appears very unwell

Related Topics

Frequently Asked Questions

References

1. Centers for Disease Control and Prevention (CDC). Pertussis (Whooping Cough).
2. Mayo Clinic. Whooping cough — Symptoms and causes.
3. MedlinePlus, U.S. National Library of Medicine. Whooping cough.
4. World Health Organization (WHO). Pertussis.