According to the NHS, respiratory infections affect the throat, sinuses, lungs, and airways and can include symptoms like cough with yellow, green, or brown phlegm; sneezing; stuffy nose; sore throat; headaches; fever; body aches; wheezing; and malaise.
The specific symptoms you experience depend on the cause. For example, the common cold is caused by a virus. Its symptoms include a runny nose, cough with yellow or green mucus, and headache. However, it typically does not cause a high fever, per Keck Medicine of USC. Pneumonia can be caused by bacteria and it can have symptoms like fatigue, wheezing, chest pain, cough with thick yellow or brown mucus, high fever, and nausea. Other common conditions under the respiratory tract umbrella include flu, bronchitis, sinusitis, bronchiolitis, chest infection, and pneumonia, per Cleveland Clinic.
The course of treatment for your phlegmy cough and feeling unwell comes down to what’s causing it. Severe viral infections might be treated with an antiviral if caught early enough; but, typically, rest, fluids, and over-the-counter pain meds are the true heroes. Bacterial infections cause more severe symptoms and require a course of antibiotics in addition to rest and fluids.