What a cold actually is
The common cold is an infection of the upper respiratory tract — the nose, sinuses, and throat — caused by viruses, most often rhinoviruses. The runny nose, sneeze, sore throat, and mild cough are not the virus damaging you directly so much as your immune response: swelling, extra mucus, and inflammation. That inflammation is uncomfortable, but it is also the body clearing the invader.
Colds run a predictable arc. Symptoms build over two to three days, peak around days three to five, then slowly fade. A lingering cough can outlast everything else by a week or two because the airway lining needs time to repair and the cough reflex stays touchy. This is normal recovery, not a sign of failed treatment.
Acute bronchitis: the cough that won't quit
Acute bronchitis is inflammation of the larger airways (the bronchi) that usually follows a cold. The hallmark is a productive cough that can last three weeks, sometimes more. People often feel they ought to be over it by now, and worry the infection is getting worse. Usually it is not — the airways are simply still inflamed and clearing themselves through mucociliary clearance.
In otherwise healthy adults, more than 90% of acute bronchitis is viral. That is the crucial number: antibiotics target bacteria, so for a viral illness they add nothing useful and carry real downsides — nausea, diarrhoea, allergic reactions, and contributing to antibiotic resistance across the whole community.
When to take it more seriously
A cold or bronchitis should not give you a high fever, breathlessness at rest, chest pain on breathing, or coughing up blood. These suggest the infection has moved deeper — possibly into pneumonia — and deserve a proper assessment. People with COPD, asthma, heart disease, or a weakened immune system have a lower threshold to seek help, because a 'simple' chest infection can destabilise them quickly.
- Fever above about 38.5°C lasting more than three days, or returning after improving
- Shortness of breath at rest, fast breathing, or bluish lips (cyanosis)
- Sharp chest pain on breathing, or coughing up blood
- Symptoms still worsening past day 10, rather than slowly easing