Causes of Chest Infection Causes of chest infection vary depending on whether the infection is viral, bacterial, or, in rare cases, fungal. Understanding the causes of chest infection helps guide treatment and determine whether medical intervention is necessary. 1. Viral Infections Most cases of acute bronchitis — the milder form of chest infection — are caused by viruses. These include: These viruses irritate the airways and lead to inflammation and mucus build-up. 2. Bacterial Infections | Causes of Chest Infection Pneumonia is often caused by bacteria such as: Bacterial chest infections are usually more serious and may require antibiotic treatment. 3. Fungal Infections Fungal chest infections are rare and usually occur in people with severely compromised immune systems, such as those with HIV/AIDS or undergoing chemotherapy. Examples include: These infections require specialised antifungal medications. 4. Risk Factors Several factors increase the likelihood of developing a chest infection: 5. Environmental Exposure Exposure to pollution, dust, or chemicals can irritate the lungs, making them more prone to infection. Living in crowded or poorly ventilated conditions also raises the risk. Whether viral or bacterial, the causes of chest infection often stem from pathogens invading a weakened or stressed respiratory system. Preventing infection involves hand hygiene, vaccination, and avoiding known risks like smoking. [Next: Symptoms of Chest Infection →]