Acute bronchitis and post-viral cough: why antibiotics don't help and what does

Acute bronchitis is the most common reason an adult seeks urgent or same-day general practice care in Australia, accounting for roughly 5% of all GP encounters. The visit often follows an upper respiratory tract infection by several days — the throat has cleared but the cough has settled in the chest, producing mucus, aching behind the sternum, and the miserable fatigue that comes with ongoing inflammation.

The clinical challenge is not diagnosis. It is managing the expectation that a chest infection means antibiotics — and explaining clearly why that expectation, in this condition, produces more harm than good.

A. Core clinical — the AU general-practice framework

What acute bronchitis is

Acute bronchitis is inflammation of the large and medium airways (the bronchi) following a viral upper respiratory tract infection. It causes cough, with or without sputum, lasting up to three weeks. A post-viral cough (also called post-infectious cough) persists after the virus has cleared — typically three to eight weeks — because of ongoing airway inflammation and temporary hyperresponsiveness.

Cough lasting three to eight weeks is called subacute. Cough lasting beyond eight weeks is chronic and warrants a separate diagnostic workup distinct from the acute bronchitis pathway.

The pathogens

More than 90% of acute bronchitis is caused by viruses: rhinovirus, coronavirus, influenza A and B, RSV, parainfluenza, adenovirus, and human metapneumovirus. Bacterial causes — Mycoplasma pneumoniae, Chlamydophila pneumoniae, and Bordetella pertussis — account for roughly 5–10% and require targeted management, not routine antibiotics.

Purulent (coloured) sputum does not indicate bacterial infection — colour reflects neutrophil debris and cellular breakdown, not aetiology. This is one of the most important misconceptions to address at the bedside.

History and examination

The RACGP guidance on viral infections and persistent cough recommends assessing:

• Cough characteristics — onset, duration, productive or dry, paroxysmal, nocturnal, any post-tussive vomiting or whoop
• Associated symptoms — fever (pattern and duration), dyspnoea, chest pain (pleuritic vs dull), haemoptysis, weight loss, night sweats
• Exposures — sick contacts, recent travel, occupation, smoking history, wood-fire or biomass exposure, pet birds
• Vaccination history — influenza, COVID-19, pertussis booster (every 10 years adult; most recent pregnancy)
• Drug history — ACE inhibitor (dry persistent cough in ~10%), OCP or recent immobility (PE risk factors)
• Risk factors for complications — age ≥65, COPD or asthma, immunocompromise, BMI ≥40, pregnancy, ATSI background, residential aged care

Examination includes vital signs (respiratory rate ≥22 is a key threshold), oxygen saturation, chest auscultation for focal crackles, wheeze, decreased air entry, and percussion for dullness. The finding of focal consolidation changes the diagnosis to pneumonia and the management pathway entirely.

Investigations — the default is none

For uncomplicated acute bronchitis with normal vital signs and a clear chest examination, no investigation is needed. This is the correct and evidence-aligned approach.

Selective investigations apply in specific circumstances:

• Chest X-ray (MBS item 58503) when focal chest examination findings are present, respiratory rate ≥22, SpO₂ below 95%, temperature ≥38.5°C persisting, age >65 with comorbidity, immunocompromise, cough exceeding three weeks, or suspicion of PE, TB, or malignancy
• Pertussis PCR (nasopharyngeal swab, MBS item 69494) when there is paroxysmal cough, whoop, post-tussive vomiting, infant household contact, or known case exposure
• Influenza, COVID-19, or RSV PCR when the patient is high-risk or an antiviral would be indicated
• D-dimer and CTPA when PE features are present
• Spirometry (MBS item 11506) when asthma or COPD is suspected from the history

Management — the framework

Therapeutic Guidelines (eTG) and RACGP guidance are unambiguous: no antibiotic for uncomplicated acute bronchitis.

Symptomatic care is the active treatment:

• Paracetamol 10–15 mg/kg per dose (max 4 g/day for adults) for fever and discomfort
• Ibuprofen 5–10 mg/kg per dose (max 1.2 g/day OTC adult) if not contraindicated
• Honey 1–2 teaspoons at bedtime for cough in patients aged 1 year and over — never under 12 months (botulism risk)
• Adequate hydration
• Rest
• Saline gargles for accompanying sore throat

Antibiotic stewardship counselling is an active component of the consultation, not an absence of treatment. Patients who understand why antibiotics are not indicated — and who receive a clear explanation of the expected recovery timeline — have better outcomes and lower re-attendance rates.

Delayed prescription strategy — writing a prescription with instructions to fill it only if symptoms are not improving after 7 days — reduces antibiotic dispensing by approximately 30% without worsening outcomes, per a Cochrane review by Spurling et al. (2017). This is a useful tool when patient expectation pressure is high.

B. Evidence appraisal — what the trials actually show

Antibiotics for acute bronchitis

The 2017 Cochrane meta-analysis by Smith et al. pooled evidence from multiple randomised controlled trials of antibiotics versus placebo in acute bronchitis. The results: antibiotics shortened cough duration by approximately half a day. The number needed to harm (any adverse event) was approximately 5.

This is not a close call. The benefit is marginal and the harms are real — diarrhoea, nausea, rash, Clostridioides difficile risk, and population-level antimicrobial resistance.

Bronchodilators for acute bronchitis

A 2015 Cochrane review by Becker et al. found no evidence of benefit for beta2-agonists (salbutamol) in unselected acute bronchitis. Bronchodilator use is appropriate only when wheeze and reversible airway obstruction are documented on examination or spirometry — that is, when there is a genuine asthma or post-viral bronchoconstriction component.

Honey for cough

A 2018 Cochrane review by Oduwole et al. found honey more effective than no treatment and equivalent to dextromethorphan for reducing cough frequency in children. The evidence base specifically covers children; adult data are more limited but the safety profile of honey is favourable and the intervention is supported by eTG.

Inhaled corticosteroids for post-viral cough

Small trials suggest a four to six week trial of inhaled corticosteroids (such as budesonide) may reduce cough in patients whose post-viral cough is accompanied by airway hyperresponsiveness features (wheeze, nocturnal cough, response to bronchodilator). Evidence is rated as moderate quality; this is a reasonable targeted approach in cough persisting beyond three weeks when hyperresponsiveness is suspected.

C. Targeted management — pertussis, post-viral cough, and specific subgroups

Pertussis (whooping cough)

Pertussis requires specific antibiotic treatment and is notifiable in all Australian states. Adults often present atypically — without the classic whoop — making it a diagnostic trap. Key features: paroxysmal cough episodes, post-tussive vomiting, cough persisting beyond two weeks, household contact with an infant.

Treatment per eTG:

• Adults: azithromycin 500 mg on day 1, then 250 mg on days 2–5
• Paediatric: azithromycin 10 mg/kg on day 1, then 5 mg/kg on days 2–5

High-risk household contacts (infants under 6 months, pregnant women in the third trimester) should receive post-exposure prophylaxis even without symptoms. Healthcare and childcare workers must be excluded from work for 5 days after commencing appropriate antibiotics.

Influenza and COVID-19 — antivirals in high-risk patients

Oseltamivir (PBS Authority Streamlined) is appropriate for high-risk patients with influenza within 48 hours of symptom onset. Nirmatrelvir/ritonavir and other COVID-19 antivirals apply to eligible high-risk patients within 5 days of symptom onset per current criteria. Prescribers should check current PBS criteria at the time of prescribing.

Atypical bacterial pathogens

Mycoplasma pneumoniae and Chlamydophila pneumoniae occasionally cause community-acquired bronchitis, particularly in household clusters and in specific risk groups. When clinically suspected: doxycycline 100 mg twice daily for 7 days (adults), or a macrolide alternative.

Post-viral airway hyperresponsiveness

When cough persists beyond three weeks with features suggesting airway hyperresponsiveness (nocturnal worsening, wheeze on examination, response to salbutamol), a trial of inhaled budesonide for four to six weeks is reasonable. If this does not resolve the cough by eight weeks, the workup shifts to chronic cough — including asthma, upper airway cough syndrome (post-nasal drip), gastro-oesophageal reflux disease, and ACE inhibitor side effect.

D. Australian operations

MBS billing

• Standard GP consultations: items 23, 36, 44
• Telehealth (video): items 91790, 91800; phone: 91890, 91891
• Chest X-ray PA and lateral: item 58503
• Pertussis PCR: item 69494
• Spirometry pre/post bronchodilator (GP-initiated): item 11506
• GPCCMP preparation and review (items 965/967) — applicable when chronic respiratory diagnosis (asthma, COPD) coexists or is confirmed
• ATSI Health Assessment: item 715

PBS prescribing

• Azithromycin, doxycycline — general schedule
• Salbutamol inhaler — general schedule (also available OTC short-course)
• Inhaled corticosteroids (budesonide, fluticasone) — Authority Required (Streamlined) for asthma
• Oseltamivir — Authority Required (Streamlined) for influenza in high-risk patients per PBS season criteria
• Codeine — Schedule 8 prescription-only since February 2018; not indicated for viral cough
• Pholcodine — withdrawn from Australian market March 2023 (TGA notification)

Notifiable diseases

Pertussis, tuberculosis, influenza (in some states), COVID-19 (in some states), and Legionella are all notifiable to the state Department of Health. Prompt notification supports contact tracing and outbreak management, particularly for pertussis near infant contacts.

Vaccination at every cough encounter

A GP encounter for acute bronchitis or post-viral cough is a natural opportunity to check:

• Influenza (annual)
• COVID-19 (per current ATAGI schedule)
• Pertussis booster (10-yearly adult; offered in pregnancy at 20–32 weeks)

E. Special populations

Children under 6 years. Over-the-counter cough and cold preparations are not recommended by the TGA. Honey (from age 1 year), saline nasal spray, and paracetamol or ibuprofen (age-appropriate dosing) are the practical options. Never give honey to infants under 12 months.

Pregnant women. Ibuprofen is avoided after 20 weeks of gestation. Paracetamol remains appropriate. Pertussis vaccination is recommended at 20–32 weeks of each pregnancy regardless of prior vaccination. Pertussis in a pregnant woman in the third trimester requires close follow-up for the newborn.

Older adults (age 65+). Lower threshold for chest X-ray and clinical review. Consider pneumonia, heart failure (cardiac cough, orthopnoea), and PE on a broader differential. Annual influenza vaccination is particularly important in this group.

Smokers. Every acute respiratory presentation is an opportunity to discuss smoking cessation — NPS MedicineWise, the Lung Foundation, and the Quitline (13 78 48) provide patient resources. A cough in a smoker over 40 that persists beyond three weeks warrants a chest X-ray to exclude malignancy.

Immunocompromised patients. A lower threshold for investigation applies. Atypical organisms, reactivation TB, and fungal infections can all present as productive cough. Involve specialist input early for patients on chemotherapy, biological agents, or with haematological malignancy.

When to escalate

Arrange emergency transfer or urgent same-day review for:

• Hypoxia (SpO₂ below 95% on room air) or respiratory distress
• Suspected PE (pleuritic chest pain, dyspnoea, haemoptysis, risk factors)
• Suspected pneumonia with sepsis features
• Suspected TB (cough >3 weeks, weight loss, night sweats, haemoptysis, origin from or travel to endemic area)
• Significant haemoptysis

Arrange same-week review for:

• Pneumonia confirmed but managed as outpatient
• Suspected pertussis with infant in household
• Recurrent bronchitis suggesting possible bronchiectasis

Arrange routine respiratory specialist review for:

• Unexplained chronic cough beyond 8 weeks despite a therapeutic trial
• Suspected lung cancer, TB, or interstitial lung disease
• Asthma or COPD requiring formal characterisation

What this article is and is not

This is general health information based on current Australian general practice guidelines including Therapeutic Guidelines, RACGP guidance, NPS MedicineWise, the Lung Foundation, and Cochrane evidence. It does not constitute personal medical advice and does not create a doctor–patient relationship. Decisions about individual treatment, including whether investigation or specific medication is appropriate, are made with a treating clinician who knows the full clinical picture.

For patient-level information: HealthDirect — Bronchitis, Lung Foundation Australia, and Better Health Channel.

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Sources cited

1. RACGP — Viral infections and persistent cough
2. RACGP AJGP — Antimicrobials for respiratory infections (2022)
3. Therapeutic Guidelines (eTG)
4. Australian Medicines Handbook
5. NPS MedicineWise — Antimicrobial stewardship
6. TGA — Codeine rescheduling (2018)
7. TGA — Pholcodine cancellation (2023)
8. TGA — Children’s cough and cold medicines
9. Lung Foundation Australia — Acute bronchitis
10. Choosing Wisely Australia
11. HealthDirect — Bronchitis
12. Better Health Channel — Bronchitis
13. Smith SM et al. — Antibiotics for acute bronchitis (Cochrane 2017)
14. Spurling GKP et al. — Delayed antibiotic prescriptions (Cochrane 2017)
15. Becker LA et al. — Beta2-agonists for acute bronchitis (Cochrane 2015)
16. Oduwole O et al. — Honey for cough in children (Cochrane 2018)