- Viral infections- Most cases of acute sinusitis follow a viral upper respiratory infection caused by common cold viruses such as Rhinovirus, Enterovirius, Coxsackie virus. These are main causes of Sinusitis.
- Bacterial infections- It is commonly associated with bacteria such as Staphylococcus aureus. In such conditions bacteria tend to grow and multiply giving rise to yellowish or greenish discharge from the nose. Bacterial infection is one of the chief causes of Sinusitis.
- Fungi: In cases where immunity of the patient has been compromised (such as in HIV, ongoing chemotherapy, etc.), fungi try to grow in the sinus secretions.
Other factors and causes of Sinusitis include: