Pharyngitis or sore throat affects the pharynx or the back of the throat in human beings and the two primary causes of pharyngitis include viral and bacterial infections. While most cases of sore throat or pharyngitis are caused due to viral infections, there are other types of pharyngitis that are caused due to bacterial infections. Apart from the common causes, there are also a few risk factors that can contribute to the occurrence of this disorder.

One of the major causes of sore throat or pharyngitis is viral infection. Pharyngitis caused due to viral infections is commonly known as viral pharyngitis. These types comprise about 40-60% of all infectious pharyngitis cases and they are considered the probable symptoms for several types of viral infections. Among all the viral causes of pharyngitis, the Adenovirus is the most common. In this case, the throat often does not appear red and is quite painful. The neck lymph node also enlarges on a modest degree. The Orthomyxoviridae virus is another cause of viral pharyngitis. This virus often causes influenza and it makes its presence felt with rapid onset of high temperature, headache and generalised ache. Apart from these two, the other viruses identified as causes of sore throat or pharyngitis include the Epstein-Barr virus, the Herpes simplex virus, measles and the common cold viruses like rhinovirus, coronavirus, respiratory syncytial virus, parainfluenza virus, etc. Illnesses like Mononucleosis (mono), chicken pox, croup, etc. are also considered probable causes of pharyngitis. Sometimes, the primary HIV virus is a probable reason behind pharyngitis as well.

Bacterial infection is a primary cause for sore throat or pharyngitis. The bacteria infected types of pharyngitis are called bacterial pharyngitis and these types usually occur due to infection of the human throat. The Group A streptococcus bacteria is the most common among all bacterial causes of pharyngitis. The pharyngitis that occurs due to these bacteria is known as Streptococcal pharyngitis and is considered one of the severe types of pharyngitis. This group of bacteria is responsible behind development of about 15-30% of all cases of pharyngitis and its common symptoms include enlarged and tender lymph glands, with bright red, inflamed, and swollen throat of sudden onset with severe pain. The other bacteria causing pharyngitis include the Corynebacterium diphtheriae, Neisseria gonorrhoeae, Chlamydophila pneumoniae, and Mycoplasma pneumoniae, etc.

Both viruses and bacteria enter a person`s body through mouth or nose and cause sore throat or pharyngitis. Viruses and bacteria may enter the body either because of breathing in particles that are released into the air when someone coughs or sneezes. These may also enter one`s body for having contact with an infected person or using shared objects like utensils, towels, toys, doorknobs or a telephone. However, sometimes it becomes almost impossible to distinguish between pharyngitis caused due to viral and bacterial infections.

Apart from the viral and bacterial infections, there are also a few other factors considered as probable causes of sore throat or pharyngitis. These factors include fungal infections, irritants like pollutants or chemical substances, allergies, dryness, pollution and other irritants, muscle strain, acid gastroesophageal reflux disease (GERD), HIV infection, tumours, tonsillitis, mumps, sinusitis, etc. The fungal infection like Candida albicans is a cause of pharyngitis and sometimes, the Fusobacterium necrophorum may also cause sore throat. In rare occasions, leukemia may lead to sore throat as well. The risk factors for sore throat or pharyngitis include excessive smoking and talking, frequent sinus infections, etc. The people who use their voice frequently as in certain professions like singing, acting and teaching have a higher risk of suffering from pharyngitis.

The above mentioned factors have mostly been found to cause sore throat or pharyngitis. However, there may be a few other factors that are not common but can cause the disease. Knowing the causes of sore throat or pharyngitis helps a lot in choosing the right kind of treatment for the disease.