Overview and the importance of their differences

Distinguishing between similar health conditions may be difficult, especially in moments of stress. Croup and pertussis are both infections of the respiratory system affecting largely babies and young children. Telling them apart is crucial for understanding how patients can be diagnosed and treated by their doctor as well as how the condition may progress. This article will clearly outline the defining features of both infections and emphasize the key differences between the two and what this means for the affected individual.

Overview of croup

Definition and causes

When an irritant enters the airway, the body fights back against this irritation which subsequently causes inflammation of the affected area. In croup, the irritant is often a virus, commonly the parainfluenza virus.¹ The virus enters the airway through contaminated air particles or surfaces.

The term ‘croup’ includes the descriptions of laryngotracheitis, laryngotracheobronchitis, and laryngotracheobronchopneumonitis.² These confusing words simply describe the parts of the airway affected by this inflammation and help doctors understand how far the infection has spread.

Croup, or laryngotracheitis, is the inflammation of the larynx (voice box) and the trachea (windpipe). This inflammation may extend into the lower airway and affect the large passageways called bronchi (laryngotracheobronchitis). It may also extend even further and affect the lung tissue itself (laryngotracheobronchopneumonitis). 

Inflammation causes the airways to swell. In children under 8 years old the lowest part of the voicebox, just under their vocal cords, is the narrowest part of their airway.³ The symptoms of croup are a result of the swelling of this narrowed airway so the inflammation causes more symptoms in children than adults.¹ Adults can get the same viruses which cause croup, however, because they have bigger airways they rarely get the symptoms which characterize the condition.

Symptoms

The symptoms of croup are a result of this swelling of the narrowed airway, which blocks the airflow and makes it difficult for the child to breathe. This can result in the following symptoms as described by the NHS:

• A barking cough which imitates a seal: the forceful push of air through the narrowed airway causes the swollen vocal cords to produce a seal-like noise¹
• Breathing in is followed by a high-pitched sound: because the airway is blocked by this swelling, the flow of air in normal breathing is met with resistance²
• A hoarse voice or loss of voice: due to the involvement of vocal cords 
• Possible fever: as the body fights the virus² 

Know when to seek medical attention.

Difficulty breathing may get worse at night or when the child is distressed.²

Diagnosis

The most useful method of diagnosing croup is based on a clinical diagnosis where the doctor diagnoses based on symptoms. Tests are avoided as they are rarely necessary and may cause additional distress in the child and worsen symptoms.⁴ As explained by the Mayo Clinic the doctor may:

• Listen to the child’s breathing
• Use a stethoscope to assess the child’s breathing 
• Look at the child’s throat 
• Occasionally use X-rays if suspicion that a different condition may be more likely 

Treatment options 

Although symptoms may look scary and seeing their child distressed may be anxiety-inducing for parents, most cases of croup can be safely treated at home.⁴ As distress and crying worsen the child’s symptoms, it is important for parents to remain as calm as possible and use the usual comfort measures to soothe their child.⁴

It is understandable that some parents may feel anxious and wish to do more for their child at home. The Cleveland Clinic describes some useful home remedies:

• Using a cool mist humidifier/shower steam 
• Medication such as paracetamol or ibuprofen
• Pillow elevation for children older than 12 months 

If your child does require medical attention, doctors may prescribe:

• Corticosteroids: which decrease inflammation by reducing the body’s ‘fight back’ against the irritant, therefore lessen the swelling of the voicebox.⁵ Dexamethasone or prednisolone are common, usually through the mouth or by injection⁵
• Epinephrine: inhaled treatment which reduces airway swelling

Overview of pertussis

Definition and causes 

The irritant which causes pertussis is a bacteria, rather than a virus. Pertussis is the name given to an upper respiratory infection⁶ caused by the bacteria Bordetella pertussis. Similarly to croup, it is spread through air particles. 

Pertussis used to primarily affect babies and young children, however since the vaccine it is now associated with children under 2 months who are too young to be vaccinated⁶ or teenagers and adults who have lost their immunity. 

Studies show that infants under 12 months⁷, especially those under 6 months old⁶, are most at risk of complications and death from pertussis so prevention and timely treatment are important. 

Adults can get pertussis and although it is usually milder, some adults may develop serious and longer-lasting cases.⁶ Pertussis is also known as whooping cough because of the high-pitched ‘whoop’ associated with the strenuous gasps for breath taken between coughing episodes.

Symptoms

The symptoms of pertussis are caused by the irritation from the Bordetella pertussis bacteria which additionally releases poisons, causing airway swelling and release of mucus.⁶ The NHS describes the progression of the associated symptoms of pertussis: 

• Initial symptoms: similar to symptoms of the cold (runny nose, possible fever, sore throat) 
• After around a week: Intense coughing episodes, more common at night. May stay for 10 weeks or more⁶
• ‘Whoop’ sound in between coughs: as patients may struggle to catch their breath, however this symptom isn’t present in everyone
• Coughing up thick mucus and occasionally vomiting
• Young babies may not develop a cough but instead struggle to breathe and even turn a blue colour

The NHS 999 section explains when an ambulance should be called.

Diagnosis

Doctors use clinical symptoms together with tests to diagnose pertussis. Doctors follow the NICE guidelines which look out for: 

• A cough present for 14 days or more with no other obvious cause PLUS one or more of an: episodic cough, ‘whoop’ sound on breathing in, vomiting after coughing and difficulty breathing in infants 

When clinical symptoms raise suspicion, laboratory tests can be used as confirmation. Pertussis is diagnosed by the presence of clinical features PLUS one positive test from:

• Cultures
• PCR 
• Serology 

Treatment options

Pertussis can be treated with antibiotics if started during the first 1-2 weeks before the coughing episodes occur, however, antibiotics will not be effective if started later in the illness.⁸ Because of this, doctors may sometimes start treatment before obtaining test results. However, antibiotics are primarily to reduce the spread of infection and may not ease symptoms. There are things patients can do to manage discomfort.

Key differences between croup and pertussis

Aetiology

Clinical presentation

Diagnostic approach

Treatment

Complications and prognosis

Potential complications of croup

Croup usually resolves in children within 48 hours, however may sometimes take longer.⁹ Mortality is low, as shown in a 10 year long study where only 0.5% of intubated children died.⁹Rare complications include: 

• Pneumonia
• Too much fluid in the lungs
• A bacterial infection of your windpipe (bacterial tracheitis)⁹

Potential complications of pertussis 

Adults often recover well from pertussis, with complications which may occur as a result of the intense coughing episodes. However, in babies and children complications can be serious and even life-threatening for babies under 6 months. Hospital treatment may be required as this will provide the best care. 

The complications to be aware of in infants include: 

• Pneumonia
• Seizures or brain dysfunction: however this is rare occurring in less than 2% of cases¹⁰
• Stopped breathing¹¹
• Dehydration¹¹

Prevention strategies

Both infections are very contagious. To prevent their spread, children with croup should stay home until their fever has passed⁵ whereas patients with pertussis without antibiotics are contagious from 6 days after the start of initial symptoms to 3 weeks after the coughing begins.¹²

Good hygiene of hands and the child’s surrounding environment is most important in preventing transmission of croup. These hygiene practices are also important in preventing pertussis, along with the pertussis vaccination and preventative antibiotics for people who may have come into contact with the bacteria and are at high risk of catching the infection.¹³

Summary

Although croup and pertussis are both very contagious respiratory infections, they differ in clinical presentation, the part of the respiratory system they affect and the causes of the illness. Distinguishing between them is important for understanding the expected diagnostic process, treatment offered and possible complications.