17.5 — Respiratory Infections

Respiratory infections are the commonest illness humans experience. An adult has 2 to 4 colds a year; a young child has 6 to 12, which is normal and is how the immune repertoire is built.

And the great majority are viral, self-limiting, and need nothing but time.

The useful skill is telling those apart from the small minority that need treatment — and the signs that separate them are mostly things you can observe yourself.

Upper respiratory tract

The common cold

Runny nose, sore throat, cough, sneezing, mild fever. Peaks at days 2 to 3, resolves over 7 to 10 days, and the cough can persist for 2 to 3 weeks.

That trailing cough is the commonest reason people return convinced something is wrong. Post-viral cough lasting up to three weeks is normal, and it reflects airway inflammation rather than continuing infection.

Green or yellow mucus does not mean bacterial infection (Chapter 17.2). It is neutrophil enzymes, and it appears in ordinary colds.

What helps: fluids, rest, paracetamol or ibuprofen, saline nasal rinse, honey for cough in anyone over one year — which has better evidence than most cough medicines — and steam if it feels good, though it does not shorten anything.

What does not: antibiotics.

Sore throat

Around 70 to 90 percent are viral.

And distinguishing streptococcal from viral matters because of the rheumatic fever risk (Chapter 17.1), particularly where that disease is still common.

The features suggesting bacterial infection, scored formally in several systems: fever, tonsillar exudate, tender neck nodes, and — importantly — the absence of cough.

A sore throat with a runny nose, cough and hoarseness is viral.

Antibiotics for streptococcal throat shorten symptoms by about a day and reduce rheumatic fever substantially, which is why the calculation differs between settings: in a high-income country with almost no rheumatic fever, the case for treating is weak; where rheumatic heart disease is common, it is strong.

Glandular fever (Epstein–Barr) — severe sore throat, marked fatigue, enlarged nodes and often a large spleen.

Two practical points. Amoxicillin given to someone with glandular fever causes a florid rash in the great majority, which is not a penicillin allergy and is frequently recorded as one. And contact sports are avoided for several weeks because of splenic rupture risk (Chapter 7.8).

Sinusitis

Facial pain worse on leaning forward, blocked nose, discharge (Chapter 5.2).

Most are viral and resolve within 10 days. Bacterial infection is suggested by symptoms persisting beyond 10 days, or by a distinctive pattern: initial improvement followed by worsening.

Treatment: saline irrigation, nasal steroids, analgesia, and antibiotics reserved for prolonged or severe cases.

Ear infection

Very common in children, for the anatomical reason in Chapter 11.12.

Ear pain, fever, and reduced hearing.

And the majority resolve without antibiotics. Delayed prescribing — a prescription to use only if not improving in 2 to 3 days — reduces antibiotic use substantially without worsening outcomes, and it is a genuinely useful compromise.

Antibiotics are given without delay in children under 2 with bilateral infection, in perforation with discharge, and in those who are systemically unwell.

Croup and epiglottitis

Croup — barking cough, harsh noise on inspiration, worse at night, in young children (Chapter 8.1).

A single dose of oral steroid is highly effective, and it has transformed a frightening illness into one usually managed without admission.

Epiglottitis — now rare where Hib vaccination is routine.

Lower respiratory tract

Acute bronchitis

Cough with sputum, in an otherwise well person, without the signs of pneumonia.

Overwhelmingly viral, and self-limiting over 2 to 3 weeks.

Antibiotics shorten it by around half a day and cause side effects in around a fifth of people. It remains one of the largest sources of unnecessary prescribing.

Pneumonia

Infection of the lung tissue itself, and this is the one that matters.

Cough, fever, breathlessness, chest pain worse on breathing (Chapter 8.2), and sputum.

In older people it frequently presents without any of those — as confusion, a fall, or simply not being right. Fever may be absent, and a low temperature is more concerning than a high one.

The signs that separate pneumonia from bronchitis: raised respiratory rate, low oxygen saturation, focal findings on chest examination, and looking unwell.

Respiratory rate is the most useful and the most often not counted (Chapter 16.4).

Severity is scored, and the components are worth knowing because they are all observable: confusion, urea, respiratory rate above 30, low blood pressure, and age over 65.

Community-acquired pneumonia — commonest organisms are Streptococcus pneumoniae, and viral causes including influenza and COVID-19.

Hospital-acquired pneumonia — different organisms, more resistant, worse outcomes.

Aspiration pneumonia — after inhaling gastric contents or food, and it is a leading cause of death after stroke (Chapter 6.3).

Treatment: antibiotics guided by severity and local patterns, oxygen, fluids. Most mild cases are treated at home.

And prevention is where the largest gains are: pneumococcal and influenza vaccination in those at risk, not smoking, and — after stroke — swallow assessment before anything by mouth.

Influenza

Abrupt onset — people frequently recall the hour — with fever, severe muscle aches, headache and profound fatigue.

And those symptoms are largely interferon effects rather than direct viral damage (Chapter 13.1), which is why they are so systemic.

The distinction from a cold is genuinely useful: a cold builds over a day or two and you can function; influenza arrives suddenly and puts you to bed.

Antivirals shorten it by around a day if started within 48 hours, and are used mainly in those at risk of complications.

Annual vaccination is needed because the virus changes constantly (Chapter 13.5), and its effectiveness varies year to year with how well the strains were predicted. Even in a poorly matched year it reduces severe disease and death, which is the outcome that matters.

The 1918 pandemic killed an estimated 50 million people, and pandemic preparedness remains built around influenza for good reason.

COVID-19

And it is worth including as an established disease rather than an event.

SARS-CoV-2 causes a spectrum from asymptomatic to fatal, with severity strongly determined by age, vaccination status and comorbidity.

Loss of smell with a clear nose was its most distinctive early feature (Chapter 11.7).

Vaccination substantially reduces severe disease, hospitalisation and death, and the protection against infection wanes faster than the protection against severe disease — which is why boosters target the vulnerable.

Antivirals are available and most effective when started early in high-risk patients.

Long COVID — persistent symptoms beyond 12 weeks, most commonly fatigue, breathlessness, cognitive difficulty and post-exertional worsening. It is real, it affects a meaningful minority, and its mechanisms are not established. The honest position is uncertainty about cause and a growing evidence base on management, and dismissing it repeats the pattern in Chapter 16.1.

Whooping cough

Weeks of paroxysmal coughing, often ending in vomiting, with the characteristic whoop in children.

In adults it presents as a prolonged cough without the whoop, and is frequently undiagnosed — which is how it reaches infants.

And infants are where it kills. Maternal vaccination in pregnancy reduces infant whooping cough by around 90 percent (Chapter 13.3), which makes it one of the highest-value vaccines in the schedule.

Bronchiolitis

RSV in infants under two. Coryza then wheeze, breathlessness and feeding difficulty.

Mostly managed supportively, and severity is judged by feeding, work of breathing and oxygen saturation.

And there has been a genuine advance: a long-acting monoclonal antibody given to all infants, and a maternal vaccine, both substantially reduce hospital admission — the first effective prevention for a condition that fills paediatric wards every winter.

When to seek help

A practical list, and it applies across all of the above.

Difficulty breathing, or breathing fast.Chest pain.Coughing blood.Confusion or drowsiness.Symptoms of a cold that improve and then markedly worsen.Fever persisting beyond 5 days.Inability to keep fluids down.In an infant: poor feeding, grunting, chest recession, or fewer wet nappies.And in anyone with a chronic lung condition or immunosuppression, a lower threshold throughout.

What is improving

Vaccination has removed several of these from ordinary experience — Hib epiglottitis, most invasive pneumococcal disease, and increasingly RSV.

Antibiotic stewardship is reducing unnecessary prescribing without worsening outcomes.

And oxygen saturation monitoring, which was hospital equipment a generation ago, is now cheap and available — with the caveat about skin pigmentation in Chapter 8.4.

What the next page fixes

Chapter 17.6 covers the other infections everybody gets — gut infections, why most need no treatment, and the one intervention that has saved more children's lives than any drug.