Streptococcal infections


Streptococcal infections are any type of infection caused by a type of bacteria called streptococcal or ‘strep’ for short.

Strep infections can vary in severity from mild throat infections to pneumonia, and most can be treated with antibiotics.

There are more than 20 different types of strep bacteria, which are split into two main groups:

  • Group A strep (strep A), which are often found on the surface of the skin and inside the throat, and are a common cause of infection in adults and children.
  • Group B strep (strep B), which usually live harmlessly inside the digestive system, and in women, in the vagina. Strep B tend only to affect newborn babies and usually cause more serious types of infection. 

It is estimated that 1 in 5 pregnant women have strep B bacteria in their vagina and/or digestive system.

Strep A

Most of the different types of infections caused by strep A are unpleasant but do not usually pose a serious threat to health. They include:

  • throat infection - specifically an infection at the back of the throat which is known as pharyngitis
  • impetigo - a type of skin infection that can cause blistering of the skin
  • cellulitis - an infection of the deeper layers of the skin
  • inner ear infection 
  • sinusitis - an infection of the small air-filled cavities that are found behind the forehead and cheekbones

Read more about the symptoms of common types of strep A infections.

Strep A bacteria only pose a potentially serious threat to health if they penetrate deeper inside the tissues and organs of the body and trigger what is known as an invasive infection. Examples of invasive infection include:

  • pneumonia - an infection of the lungs
  • meningitis - an infection of the protective layer that covers the brain
  • osteomyelitis - an infection of the bone
  • necrotising fasciitis - a very serious skin infection that can cause rapid damage and then death to skin tissue and is considered to be a type of gangrene

Treating strep A infections

Some minor strep A infections, such as a throat infection and inner ear infection will get better by themselves without the need for treatment. However, minor infections involving the skin will usually require treatment with antibiotic tablets or creams.

More serious invasive strep A infections, such as pneumonia and meningitis, will need to be treated in hospital with injections of antibiotics. In some cases, surgery may be needed to remove or repair damaged tissue.

Read more about treating group A streptococcal infections.

Who is at risk of a strep A infection?

People of any age can be affected by a throat infection, sinusitis or cellulitis. Impetigo and inner ear infection are most common in children under 15 years of age.

More serious invasive strep A infections usually affect people with a weakened immune system, which is the body’s natural defence against infection. This can be due to:

Read more about the causes of streptococcal infections.

Strep B

Most people quickly develop a natural immunity to strep B, so these types of infection are much rarer and tend only to affect newborn babies.

As newborn babies have a poorly developed immune system strep B infections can quickly spread into the body causing serious infections such as meningitis and pneumonia.

Healthcare professionals take a preventative approach to treating a strep B infection by trying to identify babies at a high risk of developing an infection and treating them with antibiotics before they are born.

Read more about the treatment of strep B infections.

How common are streptococcal infections

Minor strep A infections are very common. One estimate is that one in every four sore throats is caused by a strep A infection.

More serious invasive strep A infections are much rarer.

Strep B infections are also rare, affecting only 1 in every 2,000 births.


The outlook for minor strep A infections is excellent as most people will make a full recovery and experience no long-term complications.

The outlook for more serious invasive strep A infection is poor, especially as most people who develop this type of infection have a weakened immune system. It is estimated that 1 in 4 people who develop an invasive strep A infection will die from it.

The outlook for strep B infections is also poor. Although the survival rates have improved significantly in recent years, 1 in every 10 babies with a strep B infection will die.


Bacteria are tiny, single-celled organisms that live in the body. Some can cause illness and disease and some others are good for you.
A high temperature, also known as a fever, is when someone's body temperature goes above the normal 37°C (98.6°F).
Body tissue is made up of groups of cells that perform a specific job, such as protecting the body against infection, producing movement or storing fat.  
Last updated: 26 April 2012

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