Synopsis
Distinguish self-limiting viral upper-respiratory infection from influenza and bacterial or lower-respiratory complications, using targeted antiviral treatment and safety-netting rather than routine antibiotics.
- Most acute coryzal illnesses are viral and improve with supportive care; purulent nasal discharge alone does not prove bacterial infection or justify antibiotics.
- Influenza more often causes abrupt fever, myalgia, headache, profound malaise and dry cough, but clinical features overlap with COVID-19 and other respiratory viruses.
- Assess severity and host risk: pregnancy, older age, immune suppression and chronic cardiac, respiratory, renal, hepatic or neurological disease increase complication risk.
- Use respiratory testing when it changes antiviral, isolation, outbreak or admission decisions; a negative result is interpreted against timing and sample quality.
- Offer oseltamivir according to current NICE and UKHSA treatment criteria, ideally early, and do not delay in hospitalised or severely ill eligible patients solely for a result.
- Antibiotics do not treat uncomplicated influenza or viral upper-respiratory infection; new focal consolidation, recurrent fever or clinical decline suggests bacterial complication.
- Advise hydration, appropriate analgesia, infection-control measures and clear red flags; review vaccination after recovery rather than during the acute diagnostic decision.
Key red flags
Dyspnoea, hypoxaemia, pleuritic pain, focal crackles or recurrent fever after initial improvement suggests viral pneumonitis or secondary bacterial pneumonia.
Pregnancy, immune suppression, frailty and chronic organ disease lower the threshold for testing, antiviral treatment and same-day clinical review.
Investigation priorities
Identify influenza, SARS-CoV-2 or another virus when the result changes treatment or infection control.
Management branches
Symptoms remain confined to the upper airway with stable observations, hydration and no high-risk host factor.
- Explain the likely viral course, review analgesic contraindications and advise fluids, rest, hand hygiene and respiratory etiquette.
- Avoid routine antibiotics and low-value testing, while considering COVID-19 or influenza testing when current public-health or treatment rules make it useful.
- Give a specific review trigger for breathlessness, dehydration, confusion, chest pain, recurrent fever or deterioration after initial improvement.
Key medicines
OseltamivirUsual adult treatment is 75 mg orally twice daily for five days, with renal adjustment and specialist extension for selected cases.Adjust to current renal function and review vomiting and neuropsychiatric symptoms. Pregnancy is an influenza risk state and is not, by itself, a reason to withhold indicated treatment; use current UKHSA pregnancy guidance and seek specialist advice for severe immune suppression, complicated disease or treatment failure.
ParacetamolUse 500 mg to 1 g orally up to four times daily, maximum 4 g in 24 hours for most adults.Reduce maximum exposure in low body weight, liver disease, malnutrition or heavy alcohol use and check combination cold remedies to prevent inadvertent overdose.