Respiratory
An 8 year old child is brought into the Emergency Department with a 1 week history of a violent paroxysmal cough. A classmate has recently been diagnosed with whooping cough. How should the diagnosis be confirmed in this patient?
Answer:
PCR, a molecular technique used to detect DNA sequences of B. pertussis, is suitable for people of all age groups with a cough duration of less than 21 days. PCR is usually more sensitive than culture as the organism does not need to be viable; however, PCR is less likely to be positive in people with a symptom duration of 21 days or more. Available from regional UKHSA laboratories.Pertussis
Respiratory
Last Updated: 24th February 2026
Whooping cough, also known as pertussis, is a highly infectious disease caused by the bacterium Bordetella pertussis, which produces pertussis toxin and other substances which are believed to have an important pathogenic role in the disease. Whooping cough is now relatively rare compared with the pre-vaccination era. Whooping cough is a notifiable disease.
Clinical disease
The incubation period is about 7 - 10 days (range 5 - 21 days). Whooping cough is spread by aerosol droplets released during coughing and is considered to be infectious for from onset of symptoms until 48 hours of appropriate antibiotic treatment OR for 21 days from onset of symptoms if appropriate antibiotic therapy has not been completed.
- Catarrhal phase
- The catarrhal phase lasts between one and two weeks. Pertussis is rarely diagnosed during this stage unless there has been contact with a person who is known to be infected.
- Symptoms are often difficult to distinguish from those of other upper respiratory tract infections, and include: nasal discharge, conjunctivitis, malaise, sore throat, low-grade fever, dry, unproductive cough.
- Paroxysmal phase
- The paroxysmal phase typically occurs about 1 week after the catarrhal phase and lasts between one and six weeks. Between coughing fits (paroxysms), the person is usually relatively well, and has undisturbed sleep. The paroxysmal episodes during this phase:
- Typically consist of a short expiratory burst followed by an inspiratory gasp, causing the 'whoop' sound. The ‘whoop’ is less common in adults, and in children younger than 3 months of age (who may present with apnoea alone).
- May be severe enough to cause cyanosis in children, and are frequently associated with post-tussive vomiting. Adults may experience sweating attacks with facial flushing, and rarely, cough syncope.
- The paroxysmal phase typically occurs about 1 week after the catarrhal phase and lasts between one and six weeks. Between coughing fits (paroxysms), the person is usually relatively well, and has undisturbed sleep. The paroxysmal episodes during this phase:
- Convalescent phase
- A protracted cough can last for up to 3 months (convalescent phase), during which there is a gradual improvement in cough frequency and severity.
A previously infected person can become re-infected with pertussis, but subsequent infections are usually less severe. Vaccination does not always prevent infection, but it usually attenuates the disease.
Complications
Complications include:
- Secondary bacterial bronchopneumonia
- Secondary bacterial otitis media
- Apnoea following coughing spasms
- Seizures
- Encephalopathy
- Unilateral hearing loss
- Complications due to violent prolonged coughing
- Pneumothorax, abdominal/inguinal hernia formation, rectal prolapse, rib fracture, herniation of lumbar intervertebral discs, urinary incontinence, subconjunctival or scleral haemorrhage, facial/truncal petechiae, post-coughing vomiting leading to dehydration/malnutrition
Diagnosis
Laboratory confirmation of clinically suspected cases of whooping cough can be made by culture, polymerase chain reaction (PCR), serological testing, or oral fluid testing (OFT).
The local health protection team will advise on appropriate tests for confirmation and surveillance, this will depend on the person's age, duration of symptoms, and local laboratory facilities. The following tests are available:
- Culture and isolation of Bordetella pertussis (from nasopharyngeal aspirate [NPA] or nasopharyngeal swab [NPS]/pernasal swab [PNS]) is suitable for people of all age groups with a cough duration of less than 21 days. Available from NHS laboratories, confirmed isolates are sent to the Respiratory and Vaccine Preventable Bacteria Reference Unit (RVPBRU).
- PCR, a molecular technique used to detect DNA sequences of B. pertussis, is suitable for people of all age groups with a cough duration of less than 21 days. PCR is usually more sensitive than culture as the organism does not need to be viable; however, PCR is less likely to be positive in people with a symptom duration of 21 days or more. Available from regional UKHSA laboratories. Positive samples are sent to RVPBRU.
- Serology is suitable for older children (aged over 16 years old) and adults with more than 14 days history of cough and at least one year after the most recent dose of whooping cough vaccine (including any dose administered in pregnancy). Serology detects antibodies to the whooping cough toxin. It may be suitable in people with a cough duration of 21 days or more, when culture and PCR are unlikely to yield positive results. Available from RVPBRU.
- OFT is suitable for people aged between 2–16 years (that is, aged 2 to under 17 years) with a history of more than 14 days of cough and at least one year after the most recent dose of whooping cough vaccine. They are tested for anti-pertussis toxin immunoglobulin G (IgG). The OF kits are sent to the patient at notification by the health protection team and samples tested and reported by the RVPBRU.
Treatment
Arrange admission if the person:
- Is 6 months of age or younger and acutely unwell.
- Has significant breathing difficulties (for example apnoea episodes, severe paroxysms, or cyanosis).
- Has a significant complication (for example seizures or pneumonia)
If admission is not needed, prescribe an antibiotic if the onset of cough is within the previous 21 days. A macrolide antibiotic is recommended first line: clarithromycin for infants < 1 month old, clarithromycin or azithromycin for children and adults and erythromycin for pregnant women. Co-trimoxazole is indicated if macrolides are contraindicated or not tolerated.
Otherwise, the mainstay of treatment is supportive and early treatment of secondary bacterial infections.
Prevention
Advise that children and healthcare workers who have suspected or confirmed whooping cough should stay off nursery, school, or work until 48 hours of appropriate antibiotic treatment has been completed, or 21 days after onset of symptoms if not treated. People who work in other settings should avoid contact with infants under one year of age who are unvaccinated or partially vaccinated until 48 hours of appropriate antibiotic treatment has been completed, or 21 days after onset of symptoms if not treated.
Offer antibiotic prophylaxis to close contacts of the ‘index case’ with suspected or confirmed pertussis (such as those living in the same household, or with overnight stays in the same room in an institutional setting), when the symptoms in the 'index case’ occurred within the previous 21 days, and the close contact is at increased risk of severe complications from pertussis (e.g. unvaccinated infants < 1 years) or when the close contact is at increased risk of transmitting infection to high-risk individuals (e.g. unvaccinated healthcare workers, pregnant women ≥ 32 weeks gestation).
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
