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A preschool teacher sneezes into her hand at 9am and wipes down a table two minutes later. Three days on, half her class has a runny nose. That’s how most respiratory infections travel: not through dramatic outbreaks, but through ordinary contact, shared air, and hands that touch everything.
Adults pick up roughly two to four of these infections a year. Children in childcare can hit eight or ten. Most are mild and resolve without treatment, yet the top 7 common respiratory infections below still drive an enormous share of GP appointments, missed workdays, and antibiotic prescriptions that were never going to help.
Knowing which one you’re probably dealing with changes what you do next, from whether antibiotics are worth asking for to whether you should stay home.
Why So Many Infections Start in the Same Place
Your airway is one continuous corridor: nose, sinuses, throat, voice box, windpipe, bronchi, and finally the alveoli, the tiny sacs where oxygen crosses into your blood. Infections get named for where they settle. A cold lives in the upper airway. Pneumonia pushes deep into lung tissue.
That shared anatomy explains the overlap. A runny nose, scratchy throat, and cough can belong to any of half a dozen conditions in the first few days. Location and timing are what separate them. If you want the broader map of how these sit alongside chronic lung conditions, this plain-English guide to respiratory diseases, from asthma to COPD covers the territory well.
1. The Common Cold
More than 200 viruses cause colds, with rhinoviruses responsible for roughly half. Symptoms creep in over a day or two: a scratchy throat first, then sneezing, clear mucus, mild tiredness, and sometimes a low fever in children.
They peak around day two or three and are mostly gone by day seven to ten. A dry cough can hang around for two or three weeks while the airway lining repairs itself. That tail end is normal, provided everything else is improving.
Antibiotics do nothing here. Neither do most over-the-counter cold remedies beyond modest symptom relief, which is worth remembering before you spend £12 on a combination sachet.
2. Influenza (the Flu)
Flu announces itself. Most people can name the hour they started feeling awful. Fever climbing to 38-40°C, shaking chills, headache, aching in the back and legs, a dry cough, and exhaustion that makes a flight of stairs feel like a hill sprint.
Cold or flu?
Speed and severity are the giveaway. Colds drift in. Flu hits like a wall, and the whole-body symptoms outweigh anything happening in your nose.
Influenza spreads through droplets, contaminated surfaces, and a contagious window that opens about a day before symptoms appear. That pre-symptomatic spread is a big reason flu tears through schools and offices so efficiently, a pattern it shares with several of the most contagious diseases and what makes them spread so quickly.
If you’re pregnant, over 65, or managing a long-term condition, call your doctor early. Antivirals work best within 48 hours of symptom onset and the window closes fast.
3. COVID-19
COVID overlaps heavily with flu. A few features still point toward it: loss of smell or taste, a sore throat that arrives before the cough, and a cough that tends to peak around day five to seven rather than day two. Some people get diarrhoea or nausea first.
Rapid antigen tests are most reliable once symptoms are established, ideally two or three days in. A negative result on day one proves very little, so test again 24 to 48 hours later if you’re still unwell.
Antivirals such as nirmatrelvir-ritonavir work best started within five days of symptoms beginning. That short window is the main argument for testing early rather than toughing it out.
4. Sinusitis
Pressure behind the cheeks, forehead, or the bridge of the nose. A blocked nose. Thick mucus. A dull headache that worsens when you bend forward, and sometimes aching in the upper teeth, which surprises people until they learn the sinus floor sits right above the tooth roots.
Most cases begin as an ordinary viral cold that inflames the sinus lining. The mucus colour tells you almost nothing; green reflects immune cells doing their job, not bacteria moving in.
When sinusitis is likely bacterial
Doctors lean on two patterns. Symptoms that persist past ten days without improving, or the double-worsening pattern where you feel better around day five and then distinctly worse. Those are the cases where antibiotics get discussed.
5. Pharyngitis and Tonsillitis
Most sore throats are viral and arrive with a cough, runny nose, and hoarse voice. Strep throat behaves differently: sudden severe pain, fever, swollen red tonsils with possible white patches, and usually no cough at all. Young children often vomit or complain of stomach pain before they mention their throat.
A rapid strep test takes minutes and is worth requesting. Untreated strep carries a small but real risk of rheumatic fever. Fewer than one in ten adult sore throats turn out to be bacterial, though, so most people leave the pharmacy with lozenges rather than a prescription.
6. Acute Bronchitis
This is the infection that leaves you coughing for weeks after everything else settles. The bronchi become inflamed and mucus production climbs. Expect a productive cough, chest soreness from the effort of coughing, and mild wheezing. Fever is usually low-grade or absent.
Around 90% of cases are viral, and antibiotics don’t shorten them. Trials have found no meaningful difference in how long the cough lasts. Honey, steam, and time do about as much as anything on the shelf.
A cough that drags past eight weeks has left bronchitis behind and moved into different territory. If that’s where you’ve landed, these causes of chronic cough and what’s really keeping you coughing are the next thing to read.
7. Pneumonia
Pneumonia is the one that can turn serious quickly. Infection reaches the alveoli, which fill with fluid and pus, so oxygen transfer drops. Watch for fever with shaking chills, a wet cough, breathlessness even while sitting still, sharp chest pain on inhalation, and fatigue well beyond ordinary tiredness.
Older adults often skip the textbook picture entirely. A 78-year-old may present with confusion, sudden weakness, or losing interest in food rather than a fever. Anyone over 65, a current or former smoker, or someone living with COPD should be assessed the same day. The risk factors for COPD and which ones you can change are worth understanding, because damaged lungs handle a chest infection far less gracefully.
Signs It’s Time to Stop Waiting It Out
Most of these infections are self-limiting. A minority are not, and the difference usually shows up in a handful of specific signs:
- Breathlessness at rest, or needing to prop yourself upright to breathe comfortably
- Lips, face, or fingertips turning blue or grey
- Fever above 39.5°C that won’t budge with paracetamol or ibuprofen, or any fever lasting beyond five days
- Chest pain that sharpens when you inhale
- Confusion, unusual drowsiness, or a child who is difficult to rouse
- Coughing up blood
- Unable to keep fluids down, or signs of dehydration such as dark urine and dizziness on standing
- New wheezing or a whistling sound on breathing out, which can be the first appearance of asthma. The asthma symptoms people usually miss are easy to write off as a lingering cold
What Actually Helps While You Recover
Very little shortens a respiratory infection once it’s underway. A few things genuinely take the edge off:
- Honey. A spoonful before bed outperformed dextromethorphan in a couple of trials. Not for babies under 12 months, ever.
- Saline nasal rinses. Cheap, low-risk, and decent evidence for reducing congestion and shortening sinus symptoms. Use distilled or boiled-and-cooled water.
- Fluids and humidified air. Neither cures anything, but thick secretions are easier to shift when you’re hydrated and the air isn’t bone dry.
- Sleep. In the classic 2015 Carnegie Mellon study, people sleeping under six hours a night were more than four times likelier to catch a cold after exposure than those getting seven or more.
Prevention is less glamorous and more effective. Wash hands when you come in from anywhere crowded; it’s still the single best-value habit going. Crack windows or run a filter when people share a room, since CO2 build-up is a rough proxy for how much of everyone else’s breath you’re inhaling. Keep flu and COVID vaccines current, and if you’re over 65 or have a lung condition, ask about the pneumococcal vaccine.
And when you’re the one sneezing, the table-wiping teacher had the right instinct. Cover the cough, bin the tissue, and give yourself a day or two before you’re back in the middle of everyone.
