Pertussis (Whooping Cough)

How pertussis spreads

Pertussis spreads through respiratory droplets when an infected person coughs or sneezes. It is one of the most contagious diseases: an unprotected person living with someone who has it is very likely to be infected. People are most contagious in the first 2 weeks, during the cold-like stage, often before pertussis is suspected. Without antibiotics, they can remain contagious for 3 weeks or more after coughing fits begin.

Babies are often infected by older siblings, parents or caregivers with mild or unrecognized illness.

The three stages

The total illness can last 10 weeks or more, hence the name "100-day cough".

In babies

Babies may not whoop, and the illness can be confused with bronchiolitis. Instead, they may gag, gasp, have pauses in breathing (apnea), turn blue, or struggle to feed. About a third of babies under 1 year with pertussis are hospitalized, and most deaths occur in babies under 3 months.

In teens and adults

Symptoms are often milder, especially in vaccinated people, with a prolonged cough without whooping. Coughing fits can still cause vomiting, broken ribs, hernias, fainting and urinary leakage. Adults are a key source of infection for babies.

Complications

• Babies: pneumonia, apnea, seizures, brain damage, dehydration, weight loss and death.
• Older children and adults: rib fractures, hernias, sleep loss, fainting, bleeding in the whites of the eyes, and pneumonia.

Diagnosis

• PCR test: a swab from the back of the nose (nasopharynx); most accurate in the first 3 weeks of cough and before antibiotics.
• Culture: confirms the diagnosis but is slower.
• Blood antibody tests: useful later in the illness.
• Blood count: babies often have a high lymphocyte count.

Doctors often start treatment based on symptoms and exposure before results return, especially in babies.

Treatment

• Antibiotics: azithromycin is preferred, especially for babies under 1 month. Clarithromycin, erythromycin or trimethoprim-sulfamethoxazole are alternatives. Antibiotics given early can shorten the illness; given later, they mainly prevent spread to others.
• Stay home from school, work and childcare until 5 days of antibiotics are completed.
• Supportive care: rest, fluids, small frequent feeds, a humidifier, and avoiding smoke and other cough triggers.
• Hospital care for babies and severe cases: oxygen, suction of mucus, monitoring for apnea, and IV fluids.
• Cough medicines do not help and are not recommended for young children.

Preventing spread to contacts

Preventive antibiotics are recommended for household contacts and for people at high risk, such as babies, pregnant people in the third trimester, and people who live with or care for babies.

Vaccination

The vaccine schedule in the US:

• DTaP for children: at 2, 4 and 6 months, 15 to 18 months, and 4 to 6 years.
• Tdap at age 11 to 12.
• Tdap during every pregnancy, ideally between 27 and 36 weeks. The mother's antibodies pass to the baby and protect them in the first months of life, before they can be fully vaccinated.
• Adults who never received Tdap should get one dose, especially those around babies.

Immunity from vaccines and from infection fades over time, so vaccinated people can still get pertussis, usually more mildly.

For a symptom-focused overview of the cough itself, see whooping cough.

Frequently asked questions

What are the stages of pertussis?

Pertussis has three stages: a cold-like catarrhal stage lasting 1 to 2 weeks, a paroxysmal stage with severe coughing fits lasting 1 to 6 weeks or longer, and a convalescent stage of gradual recovery over weeks to months.

Why is pertussis dangerous for babies?

Babies have small airways and immature breathing control. Instead of whooping, they may stop breathing, turn blue or have seizures. Most deaths from pertussis occur in babies under 3 months, before they are fully vaccinated.

How long is pertussis contagious?

It is most contagious during the first 2 weeks, when it looks like a cold. Without treatment, people can spread it for 3 weeks or more after coughing fits start. After 5 days of appropriate antibiotics, they are no longer considered contagious.

Why do I need a Tdap vaccine in every pregnancy?

Antibodies from the vaccine fade quickly, so a new dose in each pregnancy, ideally between 27 and 36 weeks, maximizes the antibodies passed to the baby. This protects newborns during the first months, when pertussis is most dangerous.

Can adults get pertussis if vaccinated?

Yes. Protection from childhood vaccines and Tdap fades over the years. Vaccinated adults who get pertussis usually have a milder illness, but can still spread it to babies. Staying up to date with Tdap reduces risk.