What is strep throat?

Streptococcal sore throat, or 'strep throat' for short, is an infection of the throat caused by group A Streptococcus bacteria. Common symptoms include a sore throat, chills, fever and a swollen throat and lymph nodes

Although anyone can get strep throat, it is most commonly seen in children aged between 5-15 years. It is uncommon in people aged under three or over 40. In these groups, a sore throat is more likely to have a different cause, such as a common cold or flu virus.

Lymph nodes

A small organ of the lymphatic system containing many immune cells. Lymph nodes, also known as lymph glands, are the sites where many interactions between immune cells and foreign materials occur.

Causes

Group A Streptococcus bacteria, also known as group A beta-haemolytic streptococcus (GABHS) or Streptococcus pyogenes, invade the tissues within the throat, causing a localised infection of the throat (pharyngitis) and tonsils (tonsillitis). These bacteria are also responsible for other conditions, such as impetigo. Some individuals may carry the bacteria in their nose and throat, or on the skin, and do not exhibit any signs or symptoms of an infection.

Strep throat can be passed from one person to another within droplets from coughing and sneezing, or by sharing food or drinks. For this reason, the condition often spreads among members of the same household.

Anatomy of the respiratory system showing redness and swelling due to streptococcal sore throat.Strep throat can cause a red, swollen and sore throat. 

Pharyngitis

Inflammation of the pharynx, or 'a sore throat'.

Risk factors

Risk factors that increase the likelihood of developing strep throat include:

  • Age - being aged between 5-15 years;
  • Exposure to family or household members who have the condition;
  • Crowded living conditions, and;
  • Being prone to having Streptococcus bacteria living in your throat.

Signs and symptoms

Symptoms of strep throat appear within about four days of coming into contact with an infected person. The condition can affect just the throat (pharyngitis), or both the throat and tonsils (tonsillitis).

Common signs and symptoms of strep throat include:

  • Sore throat;
  • Fever and chills;
  • Redness, swelling or white patches inside the throat;
  • Swollen lymph nodes (sometimes referred to incorrectly as 'glands') in the neck;
  • Pain when swallowing or talking, and;
  • Bad breath.

Strep throat is not usually accompanied by a cough, which can be a feature that sets it apart from a sore throat caused by infection with a virus.

A young girl with swollen tonsils and swollen lymph nodes from streptococcal sore throat.Strep throat can cause swollen lymph nodes and tonsils in a child. 

Lymph nodes

A small organ of the lymphatic system containing many immune cells. Lymph nodes, also known as lymph glands, are the sites where many interactions between immune cells and foreign materials occur.

Pharyngitis

Inflammation of the pharynx, or 'a sore throat'.

Methods for diagnosis

To diagnose strep throat, your doctor may look closely inside your throat, feel your neck, take your temperature and perform a throat swab.

During a throat swab, the throat and tonsils are gently rubbed with a sterile cotton swab, to collect a sample for laboratory testing. Laboratory testing can accurately identify if strep throat is the cause of the sore throat, although it can take several days to get a result.

A more immediate test is the rapid antigen detection test (RADT), which also uses a throat swab, but can be performed in the doctor's office. 

A blood test can also help rule out other potential causes of a sore throat, such as mononucleosis (also known as glandular fever).

Types of treatment

Treatments for strep throat aim to relieve pain, shorten the duration of illness, limit the spread of infection and reduce the risk of complications. With these aims in mind, your doctor may prescribe one or more of the following options:

Self care

To relieve pain and fever, your doctor may suggest over-the-counter pain-relief medications, such as paracetamol and ibuprofen (but not aspirin in children, due to the risk of Reye's syndrome). Similarly, saltwater gargles, soothing liquids and medicated lozenges that cool or numb the throat may be helpful. Water and rest may also be recommended to boost your immune system's natural response against infection.

Antibiotics

Although the symptoms of strep throat usually clear on their own within seven days, Streptococcus bacteria can remain without treatment. To reduce the risk of complications or further spread of the condition, antibiotics are prescribed when infection with Streptococcus bacteria has been confirmed.

The most common antibiotic for strep throat is oral penicillin. Less frequently, roxithromycin or erythromycin may be recommended if you're allergic to penicillin.

Surgery

Surgical removal of the tonsils (tonsillectomy) may be recommended if Streptococcus bacteria causes frequent tonsillitis. This procedure is conducted under general anaesthetic in a hospital or clinic. Like all surgeries, tonsillectomy is associated with the possibility of side effects, such as bleeding during or after surgery, pain and infection. However, most people recover fully within four weeks.

Immune system

The organs and cells involved in protecting the body against infection.

Rapid antigen detection test

A test that quickly detects the presence of specific disease-causing organisms commonly using a throat swab or blood sample.

Potential complications

Although most cases of strep throat are successfully treated with antibiotics, complications can arise when the condition is left untreated or keeps coming back. Possible complications include:

Spread of infection

If left untreated, an infection with Streptococcus bacteria can spread to the following areas (causing different infections):

During a strep throat infection, the body's immune system activity is increased in an effort to remove the bacteria. In some cases, this can lead to inflammation in other areas of the body, including the joints, heart, kidney and skin. It gives rise to the following conditions:

Rheumatic fever

Rheumatic fever refers to widespread inflammation in the body, following an untreated Streptococcus bacterial infection. It usually occurs about 2-4 weeks after the sore throat. In attempting to fight off the bacteria, the body's immune system mistakenly attacks the various parts of the body. Commonly, the joints, skin, heart and brain can be affected. 

While rheumatic fever leaves no lasting damage to the brain, joints or skin, it can cause permanent damage to the heart, known as rheumatic heart disease (see below). 

Rheumatic heart disease

Rheumatic heart disease is  permanent damage to the heart, following rheumatic fever. Various structures of the heart can be damaged by inflammation, including the muscle, lining or valves. It can lead to heart failure and sometimes the need for heart surgery.

Post-streptococcal glomerulonephritis

In a similar manner to rheumatic fever, an untreated strep throat infection can lead to the body's immune system damaging the kidneys, which can cause kidney disease. It generally occurs around 1-3 weeks after the sore throat.

Symptoms of post-streptococcal glomerulonephritis usually include blood in the urine, a puffy face and swollen feet and ankles. However, it usually clears on its own within a week, without causing any lasting damage.

Scarlet fever

Scarlet fever occurs typically in children and has a characteristic rough, red rash that starts on the neck and chest, before it spreads over the body. It is due to a poison released by the bacteria that cause strep throat. It can start  as early as 1-2 days after the onset of the sore throat. In the past, scarlet fever was considered to be a serious childhood disease. However, it is now treated with antibiotics.

Immune system

The organs and cells involved in protecting the body against infection.

Glomerulonephritis

A group of conditions in which the part of the kidneys that helps filter the blood is damaged.

Prognosis

The outlook for strep throat is good when the condition is correctly diagnosed and treated early with antibiotics. In most cases, the condition clears within about a week of starting treatment.

Prevention

Strep throat may be prevented by avoiding contact with people who have the condition. If contact cannot be completely avoided, regularly washing your hands and not sharing food, drinks or personal items with infected individuals may reduce the likelihood of developing strep throat.

Teaching children good hygiene habits, such as washing their hands and covering their mouths when coughing or sneezing, can also help to prevent the spread of strep throat.

If you do get strep throat, staying home and keeping children away from organised activities is recommended. Replacing toothbrushes after starting antibiotic treatment can also reduce the possibility of re-infection. Similarly, taking the full course of antibiotics prescribed by your doctor may help to limit further spread of the Streptococcus bacteria.