Strep throat – causes, symptoms, treatment

Strep throat, also called streptococcal sore throat, is an infection of the throat and tonsils caused by Streptococcal bacteria. Typical symptoms are sore throat, chills, fever, and swollen lymph nodes in the neck. Strep throat is cured by antibiotic treatment. If left untreated, strep throat can cause serious heart and kidney complications.

Sore throats can be associated with colds and flu, tonsillitis and strep throat. This page deals primarily with strep throat. Refer also to our tonsillitis and influenza (flu) pages. 

The majority of sore throats are caused by viruses, most commonly a cold or flu virus. A viral sore throat will usually get better by itself, and has a low likelihood of complications.

A sore throat caused by bacteria, however, has a higher chance of complication and requires more attention. A sore throat in children that is accompanied by headache, high fever, stomach-ache, vomiting or severe tiredness, with or without a red rash, indicates the need for a visit to a family GP.

Although many types of bacteria can cause throat infections, Streptococcus, or strep, is the most common cause of bacterial sore throat.

Strep throat is contagious. It is spread by close contact with an infected person, often by inhaling airborne droplets from an infected person’s coughs and sneezes.  It can also be spread through shared food or drinks.

Close-quarter living conditions, such as a family home, and school and university hostels, provide an ideal environment for the transmission of strep throat from one person to another.

Children between the ages of 5 and 15 years have the highest incidence of strep throat.

A strep throat infection may involve inflammation of the tonsils (bacterial tonsillitis). However, treatment of the condition is likely to be different to that for viral tonsillitis. 
Signs and symptoms

Symptoms of strep throat develop one to four days after exposure to the bacteria via airborne droplets or by direct contact with an infected person.
The most characteristic symptoms of strep throat are sore throat and painful swallowing. Other symptoms include:

Chills and fever
Swollen and tender glands (lymph nodes) on the sides of the neck
Red and swollen appearance inside the throat
Pus-like white or yellow patches or spots may be visible on the back of the throat and on the tonsils
Headache, nausea and vomiting may also be present
Body aches and pains.
Some people will develop a red skin rash that feels rough to the touch. A strep throat infection accompanied by this distinctive rash is known as scarlet fever. The rash is caused by toxins produced by the Streptococcus pyogenes bacterium. 

Potential complications of untreated strep throat infection include middle ear infection (otitis media), sinus infection (sinusitis), pneumonia, meningitis, kidney disease, and rheumatic fever. Of these, rheumatic fever and kidney disease are of most concern.

Rheumatic fever
Rheumatic fever is a serious complication of strep throat. Untreated or inadequately treated strep throat may result in bacteria remaining in the tonsils stimulating a persistent immune response.  The on-going immune response may cause inflammation in other parts of the body including the brain, heart, joints and skin. This is rheumatic fever and it usually occurs two to four weeks after a strep throat infection.

The most serious consequence of rheumatic fever is that inflammation affecting the heart can cause scarring of the heart valves, necessitating heart valve replacement surgery.  

Those at highest risk of developing rheumatic fever are young and of Maori or Pacific ethnicity living in lower socioeconomic regions of the country. The number of New Zealanders of Pacific ethnicity admitted to hospital with rheumatic fever is approximately eight times higher than the national average.  the number of Maori admitted to hospital with rheumatic fever is about twice the national average.

Visit the Ministry of Health’s rheumatic fever webpage for more information.

Kidney disease
The response of a person’s immune system to a strep throat infection may also cause inflammation of the kidneys (post-streptococcal glomerulonephritis). This form of kidney disease is more common but less serious than rheumatic fever.

It usually occurs one to three weeks after a strep throat infection, and typically resolves on its own within several days without causing any long-term kidney damage.   Children are at the highest risk of developing this condition following a strep throat infection. Symptoms may include blood in the urine, swollen ankles and puffy eyes.

Diagnosis of strep throat is important because starting antibiotic treatment within 48 hours lessens the duration of symptoms by one to two days, cuts down the risk of rheumatic fever and kidney disease, and reduces the risk of disease transmission to other people. During a GP visit, a throat culture might be taken by touching a cotton swab to the throat and tonsils. The swab is then sent to a laboratory where strep throat is confirmed by bacteriological culture and identification of the streptococcal bacteria in the throat swab.

Although throat culture is the definitive test for a strep throat infection, the results usually take 24-48 hours to come back to the GP.

A Rapid Antigen Detection Test (or RADT), which also involves taking a swab of the throat and tonsils, may also be done. Although the RADT can provide results within minutes, it is not as precise as a throat culture.

If strep throat is strongly suspected, both the throat swab and RADT may be performed and antibiotic treatment started immediately, even if the RADT test is negative, while waiting for the throat swab results to come through. If the throat swab result does not confirm streptococcal infection, the antibiotics will be stopped. 

Because of the potential for serious complications, strep throat should be treated with antibiotics as soon as possible. Antibiotics used to treat strep throat include the following:

Phenoxymethyl penicillin: is taken orally and is the most commonly prescribed antibiotic for strep throat.
Amoxicillin: is a useful oral penicillin alternative as it can be given with food, which may help people to remember to take all of their doses.
Benzathine benzylpenicillin or procaine penicillin: is given as a single intramuscular injection and may be used in patients who are unable to take penicillin orally or are unlikely to complete the 10-day oral course.
Erythromycin ethyl succinate: is a suitable oral antibiotic alternative for people who are allergic to penicillin.
With oral antibiotic treatment, the full 10-day course must be completed, even if symptoms resolve after only two to three days, to ensure that the infection does not return and to minimise the risk of developing rheumatic fever and kidney disease.

Symptom relief for sore throat can be gained from a saltwater gargle (half teaspoon of salt to a cup of warm water) and sucking throat lozenges containing ingredients that are cooling, anaesthetic, anti-septic, or anti-inflammatory.

Pain relief and reduction of fever can be obtained from use of over-the-counter paracetamol and ibuprofen.

Surgical removal of the tonsils may be recommended for people who have recurrent strep throat. Surgery does carry some risks, including bleeding during and after the operation in some people. Throat pain and difficulty eating is usual in the first few days after the operation. Full recovery typically takes two to three weeks. 

An important part of managing a strep throat infection is to prevent its spread to other people. Simple steps to help prevent the spread of strep throat include:

Covering the mouth and nose with a tissue when sneezing or coughing
Frequent and thorough washing and drying of hands
Avoiding close physical contact
Not sharing food, liquids, or eating or drinking utensils with an infected person
If strep throat is confirmed, staying home for 24 hours after starting antibiotic therapy
Support and information

Additional information about strep throat and rheumatic fever can be obtained from Healthline, which is a free 24-hour telephone advice service provided by the Ministry of Health. Healthline is staffed by registered nurses who can advise and recommend appropriate care for callers with symptoms.

Free phone: 0800 611 116

Kerdemelidis M, Lennon D, Arroll B, Peat B. Guidelines for sore throat management in New Zealand. N Z Med J. 2009;122(1301):10-8.
Khan, Z.Z. (2017). Group A streptococcal (GAS) infections (Web page). Medscape Drugs and Diseases. New York, NY: WebMD LLC. [Accessed: 25/09/17]
Ministry of Health (2017). Sore throat (Web Page). Wellington: New Zealand Government Ministry of Health. [Accessed: 25/09/17]
O’Toole, M.T. (Ed.) (2013). Rheumatic Fever. Mosby’s Dictionary of Medicine, Nursing & Health Professions (9th ed.). St Louis, MI: Elsevier Mosby.
O’Toole, M.T. (Ed.) (2013). Strep throat. Mosby’s Dictionary of Medicine, Nursing & Health Professions (9th ed.). St Louis, MI: Elsevier Mosby.
Ministry of Health (2017). Previous BPS target: Reduce rheumatic fever (Web Page). Wellington: New Zealand Government Ministry of Health. [Accessed: 25/09/17]