Pharyngitis is a sore throat caused by an infection or inflammation of the back of the throat or the pharynx. Most people associate pharyngitis with strep throat; however, there a numerous microbial causes of pharyngitis.

Typically the cause of the pharyngitis cannot be determined solely on clinical grounds as symptoms overlap broadly with few exceptions.

Strep throat is caused by group A Streptococcus bacteria./CDC
Strep throat is caused by group A Streptococcus bacteria./CDC

Streptococcal pharyngitis

Easily the most important pathogen as a cause of pharyngitis is Streptococcus pyogenes or group A strep. Clinically an inflamed and edematous pharynx is observed with the infected person complaining of throat pain and difficulty in swallowing. Also present is fever, headache, swollen lymph nodes and sometimes a red papule rash.

Other types of beta-hemolytic strep particularly groups C and G can produce similar symptoms as group A strep, only somewhat milder. Only group A strep is associated with rheumatic fever as a sequelae.

Arcanobacterium haemolyticum pharyngitis

The bacterium that causes this type of pharyngitis closely resembles streptococcal pharyngitis even including the rash in some patients. A. haemolyticum pharyngitis is frequently seen in young adults and adolescents as opposed to streptococcal pharyngitis which is primarily a disease of young children.

Viral pharyngitis

Viruses are by far the most common cause of pharyngitis in both adults and children. Epstein-Barr virus (infectious mononucleosis) is the most common virus implicated with adenoviruses and the cold viruses-coronaviruses and rhinoviruses are also common.

People with pharyngitis caused by adenoviruses frequently have viral conjunctivitis concurrently. Symptoms differ little from bacterial pharyngitis and culture and “rapid tests” are required to rule out bacterial pharyngitis.

Gonococcal pharyngitis

Many agents of sexually transmitted infections can also cause pharyngitis including Chlamydia and syphilis.

An oropharyngeal infection with gonorrhea can be asymptomatic or clinical symptoms may be present and can be seen with disseminated infection.

It may be suspected in patients that engaged in oral sex. If the physician suspects gonococcal pharyngitis he or she must indicate this so the appropriate bacteriological media is used to culture it.


Though extremely rare in the United States with less than 10 cases reported annually, it can occur sporadically. It is very easy to differentiate from red patches as seen in streptococcal pharyngitis.

Diphtheria is characterized by a thick grayish-white membrane which covers the back of the throat with swelling in the surrounding tissues.

Specimens for suspected diphtheria are typically referred to public health laboratories for identification.

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