Overview
Whooping cough, also called pertussis, is a highly contagious bacterial infection of the airways. It begins like an ordinary cold, but the cough then comes in long violent bouts that can continue for weeks or months.
It is most dangerous in babies. CDC reports that in infants under one year, the cough may be minimal or absent and pauses in breathing may be the only sign, which makes it easy to miss at the point when it is most serious.
Disease Summary
- Category
- Infectious Disease
- Cause
- Bordetella pertussis
- Transmission
- Respiratory droplets from coughing and sneezing
- Body System
- Respiratory System
- Preventable
- Yes
- Curable
- Yes
Symptoms
Common Symptoms
Symptoms usually begin 5 to 10 days after exposure, and sometimes take as long as 21 days. The illness runs in three stages.
Runny or Blocked Nose
The illness begins like a common cold, and this first stage lasts 1 to 2 weeks.
Mild Fever
CDC describes a low-grade fever in the early stage. A high fever suggests a different illness.
A Mild Cough at First
The cough starts occasional and unremarkable, which is why the diagnosis is often made late.
Violent Coughing Fits
CDC describes rapid, violent and uncontrolled coughing fits, averaging around 15 attacks in 24 hours.
A High-Pitched Whoop
The whoop is the sound of breathing in hard after a coughing fit. Not everyone makes it, and many adults never do.
Vomiting After Coughing
Being sick during or straight after a coughing fit is characteristic enough to form part of the case definition.
Exhaustion Between Fits
People are left very tired after each bout, and sleep is badly disrupted.
Pauses in Breathing in Babies
CDC states that many infants do not cough at all and instead have pauses in breathing, which may cause them to turn blue.
Danger Signs
Seek urgent medical attention immediately if any of the following symptoms develop.
Any Difficulty Breathing
CDC states plainly to seek immediate care for breathing difficulties.
Pauses in Breathing in a Baby
CDC describes these as life-threatening and reports them in 68% of infants under 12 months with whooping cough.
Turning Blue
A blue or dusky colour around the lips, gums or nail beds means the baby is not getting enough oxygen.
A Baby Under One Year With Suspected Whooping Cough
CDC states babies under one are at greatest risk, and that about one third of infants under 12 months with pertussis need hospital treatment.
Signs of Pneumonia
CDC reports pneumonia in 22% of infants under 12 months with whooping cough.
Seizures
Seizures are an uncommon but serious complication and require emergency care.
Diagnosis
History and Examination
CDC lists the history of typical signs and symptoms first, followed by physical examination. The pattern of the cough is more informative than how the chest sounds.
The Case Definition
A cough lasting two weeks or more with at least one of coughing fits, a whoop on breathing in, vomiting after coughing, or pauses in breathing.
Timing From Exposure
Symptoms usually develop 5 to 10 days after exposure, but can take up to 21 days, which matters when tracing a household outbreak.
A Swab From the Back of the Nose
CDC advises obtaining a swab or aspirate from the back of the nose in everyone with suspected whooping cough.
Choosing the Test by How Long the Cough Has Lasted
Different tests work at different stages, so the duration of the cough decides which one is useful.
Laboratory Tests
PCR From a Nose Swab
Useful up to 3 to 4 weeks after the cough begins. Beyond four weeks the bacterial DNA falls away and false negatives become common.
Culture
CDC calls culture the reference standard. It is most reliable in the first two weeks of coughing and before antibiotics start.
Antibody Blood Test
Most useful 2 to 8 weeks after the cough began, when antibody levels peak. CDC states it is not used to confirm a case.
Testing for Related Bacteria
Related organisms cause a milder similar illness. Distinguishing them matters because only one of them is whooping cough.
General Blood Tests
Used alongside the swab to build the overall clinical picture, particularly in a sick infant.
Treatment
Macrolide Antibiotics
CDC names azithromycin, clarithromycin and erythromycin. They clear the bacteria and stop the person passing it on, and CDC states treatment in the first 1 to 2 weeks, before the coughing fits begin, is most effective at reducing how severe the illness becomes.
Treatment Within the Right Window
CDC gives a window of within 3 weeks of cough onset for people aged 1 year and older, and within 6 weeks for infants under 1 year and for pregnant women near term.
Hospital Care for Babies
CDC states that about one third of infants under 12 months with whooping cough need hospital treatment, for monitoring of breathing, oxygen and feeding support.
Alternative Antibiotics
CDC names an alternative for people over 2 months who cannot take a macrolide, and states it should not be given to pregnant women, breastfeeding mothers or infants under 2 months.
Preventive Antibiotics for Close Contacts
CDC recommends these for household contacts within 21 days of the onset of cough in the case, and for people at risk of severe illness.
Prevention
Vaccinate babies on time
WHO recommends a three-dose primary series starting as early as 6 weeks of age, with doses 4 to 8 weeks apart. Starting on time matters, because the danger period is the first months of life.
Give the booster doses
WHO recommends a booster preferably during the second year of life, and national schedules add further doses in childhood and adolescence.
Vaccination in pregnancy
WHO advises vaccinating pregnant women in the second or third trimester, ideally at least 15 days before delivery, so that protective antibodies pass to the baby.
Keep coughing adults away from newborns
WHO advises that suspected cases avoid contact with infants and young children for at least the first five days of antibiotic treatment.
Preventive antibiotics for household contacts
CDC recommends these within 21 days of the onset of cough in the case, particularly where there is a baby in the house.
Treat early to stop spread
CDC states infected people remain contagious for at least 2 weeks after coughing begins unless treated.
Risk Factors
Babies Under One Year
CDC states this group is at greatest risk of both catching whooping cough and having severe complications.
- Infants too young to have completed the primary series
- CDC reports pauses in breathing in 68% of infants under 12 months
- CDC reports pneumonia in 22% of infants under 12 months
- About one third of infants under 12 months require hospital treatment
Unvaccinated and Under-Vaccinated Children
Missed or delayed doses leave children exposed during the years the illness is most severe.
- Children whose primary series was never started
- Children who missed booster doses
- Children in communities with low immunisation coverage
- Older siblings, who often bring the infection into the home
Pregnant Women and New Mothers
Vaccination in pregnancy protects the baby in the weeks before their own doses begin.
- Women in the third trimester
- Unimmunised mothers of newborns
- Pregnant women exposed to a case, who need prompt preventive treatment
- Households where a newborn is expected
People With Weakened Immunity or Severe Asthma
CDC names these groups as facing elevated risk of severe illness.
- People with immunocompromising conditions
- People with moderate to severe asthma under medical treatment
- Close contacts of these people, who are also offered preventive antibiotics
- Older adults with chronic lung disease
Complications
Pauses in Breathing
CDC reports these in 68% of infants under 12 months and describes them as life threatening.
Pneumonia
CDC reports pneumonia in 22% of infants under 12 months with whooping cough.
Hospital Admission
CDC reports that approximately one third of infants under 12 months with whooping cough require hospital treatment.
Seizures and Brain Injury
An uncommon complication caused by lack of oxygen during prolonged coughing fits or by the bacterial toxin.
Rib Fractures and Hernias in Adults
Prolonged violent coughing can crack ribs and cause hernias, particularly in older adults.
A Cough That Lasts for Months
CDC states coughing fits typically last 1 to 6 weeks but can extend to 10 weeks, and may return with later chest infections.
When to Seek Medical Care
Any Difficulty Breathing
CDC states to seek immediate care for breathing difficulties, at any age.
A Baby With Pauses in Breathing or Blue Colour
This is an emergency. It is the way whooping cough usually shows itself in the youngest babies.
Violent Coughing Fits
CDC advises consulting a health worker for violent coughing, particularly when it comes in bouts.
A Cough Lasting Two Weeks or More
Especially with coughing fits, a whoop, or vomiting after coughing.
After Known Exposure, Especially With a Baby at Home
Preventive antibiotics are recommended within 21 days of the onset of cough in the case, so contact the clinic rather than waiting for symptoms.
Prognosis
Most People Recover Fully
Recovery is gradual, with the cough becoming milder and less frequent over weeks.
Outcome Depends Strongly on Age
CDC states the risk of severe complications and death is highest in unvaccinated infants under 12 months, and that complications are usually less severe in older age groups.
Recovery Takes Weeks to Months
CDC states coughing fits typically last 1 to 6 weeks and can extend to 10 weeks, with a further convalescent period after that.
Immunity Is Not Permanent
CDC states that vaccine protection decreases over time and that infection itself does not give lifelong immunity, which is why boosters exist.
Differential Diagnosis
Viral Chest Infections
Infections such as RSV and influenza have shorter incubation periods, usually cause fever, and do not produce the paroxysms and whoop.
Atypical Pneumonia
Causes fever, crackles in the chest and raised inflammatory markers, unlike the typically fever-free later stage of whooping cough.
Cough-Variant Asthma
Features wheeze, night symptoms and a history of allergy, and improves with inhaled treatment.
Reflux
Causes a chronic cough from irritation of the airway without coughing fits or vomiting after a bout.
Inhaled Foreign Object
Starts suddenly with choking and causes one-sided chest findings, rather than the gradual build-up of whooping cough.
References
World Health Organization: Pertussis
WHO health topic page covering the disease, vaccination and global case figures.
CDC: Symptoms of Whooping Cough
The three stages of illness, symptoms in babies, and when to seek immediate care.
CDC: Clinical Features of Pertussis
Case definition, complication rates in infants and the course of illness.
CDC: Treatment of Pertussis
Recommended antibiotics, treatment windows and preventive treatment of contacts.
Frequently Asked Questions
How long does whooping cough last?
CDC states that the early cold-like symptoms last 1 to 2 weeks, then coughing fits typically last 1 to 6 weeks and can extend to 10 weeks, followed by a gradual recovery over weeks to months. The fits may return with later chest infections.
How long is someone with whooping cough contagious?
CDC states that infected people remain contagious for at least 2 weeks after coughing begins. WHO advises that suspected cases avoid contact with infants and young children for at least the first five days of antibiotic treatment.
Do antibiotics help, and when?
Yes, but timing matters. CDC states that treatment in the first 1 to 2 weeks, before the coughing fits begin, is most effective at reducing how severe the illness becomes, and that antibiotics also stop the person passing it on. Later treatment still prevents spread even if the cough continues.
Can I protect a newborn before their own vaccinations?
Yes. WHO advises vaccinating pregnant women in the second or third trimester, ideally at least 15 days before delivery, so that antibodies pass to the baby. Making sure everyone in the household is up to date also helps.
Why does my baby not cough but seem to stop breathing?
CDC states that rather than coughing, many infants have pauses in breathing, which it describes as life threatening and which may cause the baby to turn blue. CDC reports these pauses in 68% of infants under 12 months and states that in infants they may be the only symptom. Seek immediate care.