Sinusitis is not contagious, according to MedicineNet. Sinusitis, also referred to as a sinus infection, is caused by viruses, bacteria or fungi that get into the sinus cavity of the infected person and prosper there causing inflammation and blockage of the sinus airways.
Sinus infections occur when the patient's sinuses exhibit abnormalities that allow infection-causing pathogens to enter the sinus cavity. Abnormal swelling, mucus production, inflammation or nasal or facial trauma can contribute to the formation of sinusitis, according to MedicineNet. While infection is the most common cause of sinusitis, allergies and exposure to other irritants can cause sinusitis. Typical symptoms include headache, fever, cough and sore throat.