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Streptococcal infections (Group A and Group B)

Page last reviewed: 13/07/2011

Streptococcal infections are any type of infection caused by a type of bacteria called streptococci or 'strep' for short.

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

This section focuses on what are called "beta-haemolytic strep infections", and is only dealing with the two commonest types of beta-haemolytic strep Group A and Group B).

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

  • Group A strep (strep A, also known as “Streptococcus pyogenes”), 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, also known as “Streptocccus agalactiae”), 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:

  • a 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
  • scarlet fever

Strep A can also cause rheumatic fever or nephritis (inflammation of the kidneys), but these conditions are rare. 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.

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:

  • a health condition, such as type 2 diabetes or HIV
  • a side effect of treatments, such as chemotherapy or steroid medication (corticosteroids)

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.

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. It is estimated that only 1 in every 33,000 people will develop an invasive infection in any given year in Ireland.

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.  

Page last reviewed: 13/07/2011

Minor strep A infections

Throat infection

Symptoms and signs of a sore throat include:

  • swollen tonsils (two small glands found at the back of your throat, behind the tongue)
  • enlarged and tender glands in your neck
  • a painful, tender feeling at the back of your throat
  • discomfort when swallowing

Skin infections

The two most common types of strep A skin infections are:

  • Impetigo: the symptoms of impetigo begin with red sores or blisters, usually around the nose and mouth, or on the arms, trunk (torso) or legs. The sores usually burst soon after they appear, leaving thick, yellow-brown golden crusts. The crusts dry to leave a red mark that will usually heal without scarring. Impetigo is not painful, but it can make your skin feel very itchy. Read more about the symptoms of impetigo.
  • Cellulitis: cellulitis most commonly affects one of your legs but symptoms can develop in any area of your body. The condition affects your skin in several ways, causing it to become red, painful, hot, swollen and tender. If you have cellulitis, you may also find that blisters develop on your skin. Cellulitis can make you feel generally unwell, causing symptoms such as a high temperature, nausea, shivering and chills.

Other types of strep A infection

Inner ear infection

Symptoms of inner ear infection include:

  • severe earache
  • a high temperature (fever) of 38°C (100.4°F) or above
  • flu-like symptoms in children, such as vomiting and a lack of energy
  • slight deafness


Symptoms of sinusitis include:

  • a blocked or runny nose
  • a throbbing pain in your face, which is often worse when you move your head
  • a high temperature

Invasive strep A infections

The symptoms of an invasive strep A infection will depend on what type of infection develops.

For example:

  • an infection of the lungs (pneumonia) causes persistent coughing, breathing difficulties and chest pain
  • an infection of the blood (sepsis) causes high temperature, rapid heartbeat and rapid breathing
  • an infection of the protective outer layer of the brain (meningitis) causes a severe headache, vomiting, stiff neck, sensitivity to light and a distinctive blotchy red rash

Much rarer types of invasive strep A infections include:

  • scarlet fever - an infection that can affect the whole body, with the most distinctive symptom being a widespread fine pink-red rash
  • toxic shock syndrome - a serious, widespread infection of the blood and multiple organs
  • necrotising fasciitis - an infection of the deepest layer of skin that causes the affected tissue to die (the death of tissue is known as gangrene)

Strep B infections

The symptoms of strep B infection in a newborn baby often develop within the first 12 hours of giving birth, but can occur anytime in the first three months after birth. Symptoms that a newborn baby may have include:

  • being floppy and unresponsive
  • poor feeding
  • grunting when breathing
  • irritability
  • an unusually high or low temperature
  • unusually fast or slow breathing
  • an unusually fast or slow heart rate

While much rarer, strep B infections can occasionally develop in adults. These tend to take a similar form to invasive strep A infection, with symptoms depending on where in the body the infection takes place, such as pneumonia, meningitis or sepsis.

Page last reviewed: 13/07/2011

Strep A

Strep A is a group of bacteria that are a common cause of infection in humans.

Most infections are minor and are confined to either the throat, the upper airways of the head or the skin.

However, if the bacteria manage to penetrate deeper inside the body more severe infections can occur.

Minor strep A infections

Throat infections

Throat infections are spread in much the same way as a cold or the flu. If an infected person coughs or sneezes, tiny droplets of fluid that contain the bacteria are launched into the air. If you breathe these in, you may become infected.


An impetigo infection can occur when the bacteria invade otherwise healthy skin through a cut, insect bite or other injury.

An infection can also occur when the bacteria invade the skin as a result of the skin barrier being disrupted by another underlying skin condition, such as head lice, scabies or eczema.


Cellulitis usually occurs when the surface of your skin is damaged. It creates an entry point for the bacteria, allowing them to attack the skin and tissue underneath.

You are more at risk from cellulitis if you:

  • are obese (excessively overweight)
  • have a weakened immune system
  • have poorly controlled diabetes
  • have circulation problems
  • have chickenpox or shingles

Inner ear infection

Inner ear infection is caused when bacteria in the nose or throat spread up into a tube that runs between the throat and the ear.

Children are more likely to be affected by otitis media as they have a weaker immune system and the tube that runs from their throat to their ear is shorter, so it is easier for bacteria to reach it.


Most cases of sinusitis are caused by viral infections but occasionally bacteria can spread from the throat or the nose and into the sinuses.

Invasive infection

A more serious invasive strep A infection can usually only occur if someone has a wound, injury or other type of trauma that can allow bacteria into the body, and a weakened immune system.

A healthy immune system will usually prevent bacteria from spreading deeper inside the body.

The following people could have a weakened immune system:

  • babies aged less than six months
  • those over 75 years of age
  • those with a health condition that weakens the immune system, such as HIV, cancer or type 2 diabetes 
  • those who inject drugs such as heroin
  • those who misuse alcohol 

There are a number of medical treatments that can also weaken the immune system, such as:

  • chemotherapy 
  • steroid tablets (corticosteroids)
  • a type of medication called an immunosuppressant that is designed to prevent your body from rejecting a donated organ

Strep B

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

Strep B bacteria can sometimes be passed on to the baby through the amniotic fluid. Amniotic fluid is a clear liquid that surrounds and protects the unborn baby in the womb.

It is also possible for a baby to contract a strep B infection as it passes through the birth canal during labour.

In some cases, a baby can contract an infection a few months after birth, most likely by catching it from another person who is carrying Strep B

Most children and adults have a natural immunity to the strep B bacteria, though infections can sometimes occur in people with weakened immune systems.

Bacteria are tiny, single-celled organisms that live in the body. Some can cause illness and disease and some others are good for you.
The immune system is the body's defence system, which helps protect it from disease, bacteria and viruses.

Page last reviewed: 13/07/2011

Strep A

A strep A infection can be diagnosed by taking a swab of affected tissue or fluid and checking for the presence of bacteria

A blood test can also be used to check if your immune system has produced certain antibodies in response to a group A infection.

In cases of suspected an invasive group A infections, blood tests can be used to confirm whether there are actually bacteria in the blood, rather than just the antibodies.

Strep B

If your baby has symptoms that could indicate they have a strep B infection then a diagnosis can be confirmed using blood and urine tests.



Bacteria are tiny, single-celled organisms that live in the body. Some can cause illness and disease and some others are good for you.
Urine test

Urinalysis / UA is when a urine sample is tested, commonly to check for any signs of infection, or protein or sugar levels.


Useful Links

Page last reviewed: 13/07/2011

Minor strep A infections

Throat infection

A throat infection usually passes without the need for medication.

To help relieve symptoms:

  • use over-the-counter (OTC) painkillers, such as paracetamol, to help control pain and fever
  • avoid food or drink that is too hot, as they could irritate your throat
  • avoid smoking and smoky environments
  • gargle regularly with warm, salty water to help reduce any swelling or pain

Antibiotics are not recommended for most cases of throat infections as they will do little to speed up your recovery time and can cause side effects such as nausea, vomiting and diarrhoea.

In addition, using antibiotics to treat minor ailments can make them less effective in the treatment of life-threatening conditions.

Antibiotics are usually only recommended if you are more vulnerable to the effects of a throat infection due to having a weakened immune system or a serious health condition such as heart disease.

In such a circumstance a 10-day course of a penicillin class of antibiotics is usually prescribed.

If you are prescribed an antibiotic, it is important to finish the course even if you feel better. If you are allergic to penicillin, another antibiotic called erythromycin may be used.

Skin infections

Impetigo can be treated using antibiotic cream.

Cellulitis is a more deep rooted type of skin infection, so it will require a course of antibiotic tablets.

Inner ear infection

Four out of five cases of inner ear infection clear up within a few days without the need for treatment.

Over-the-counter (OTC) painkillers, such as paracetamol and ibuprofen may be used to control the symptoms of inner ear infection (pain and fever). Aspirin should not be given to children who are under 16 years of age.

Antibiotics are not recommended for the reasons discussed above unless the symptoms are particualry severe or symptoms worsen with time.


If your symptoms of sinusitis do not resolve within seven days it is likely that your GP will prescribe you a short dose of antibiotics.

Over-the-counter painkillers such as paracetamol, ibuprofen or aspirin can be used to relieve a headache, high temperature and any facial pain or tenderness.

Invasive infection

Invasive strep A infections (with the possible exception of pneumonia) are regarded as a medical emergency. Therefore, if you develop this type of infection, you are likely to be admitted to hospital. You may need to be placed in an intensive care unit (ICU).

The ICU will be able to help support any affected body function, such as breathing or blood circulation, while the medical staff will be able to focus on treating the infection.

The infection will be treated using intravenous antibiotics (injected directly into a vein). Intravenous antibiotics usually have to be given for between seven and 10 days.

If there is an identifiable source of infection, such as an infected wound, it has to be removed. This is known as source control.

Source control could involve:

  • draining the pus from an infected wound
  • surgically removing infected or dead tissue

Strep B infections

Health professionals use a preventative approach to deal with strep B infections. This means trying to identify babies who have an increased risk of being born with a strep B infection.

As a precaution, mothers of high-risk babies can be given antibiotics during their pregnancy. Alternatively, the baby can be given antibiotics shortly after birth.

Known risk factors that may mean you need to take antibiotics during pregnancy include:

  • having given birth to a previous baby with a strep B infection
  • if strep B is found in your urine during urine tests that were carried out for other purposes, such as checking if your bladder and kidneys were functioning normally
  • if strep B is found during vaginal and rectal swabs that were carried out for other purposes, such as checking if you had an infection inside your vagina (vaginosis)
  • if you have a high temperature during labour
  • if you go into labour prematurely
  • giving birth more than 18 hours after your waters have broken

If your baby develops a strep B infection after birth, they will need to be treated with intravenous antibiotics.


Antibiotics are medicines that can be used to treat infections caused by micro-organisms, usually bacteria or fungi. For example, amoxicillin, streptomycin and erythromycin.
An allergen is a substance that reacts with the body's immune system and causes an allergic reaction.
Intravenous (IV) means the injection of blood, drugs or fluids into the bloodstream through a vein.
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.
Veins are blood vessels that carry blood from the rest of the body back to the heart.

Page last reviewed: 13/07/2011

The spread of all strep bacteria can be reduced by good hygiene, such as regularly washing your hands with soap, particularly:

  • after coughing and sneezing
  • before preparing foods
  • before eating

Cuts, grazes and other wounds should be kept clean, and you should be watchful of any signs of infection, particularly if you have a weakened immune system. Signs of infection include:

  • swelling
  • redness
  • a high temperature (fever) of 38°C (100.4°F), or above
  • pus or other types of discharge
  • an unpleasant smell coming from the wound
  • pain in the area of the wound
Bacteria are tiny, single-celled organisms that live in the body. Some can cause illness and disease and some others are good for you.
Inflammation is the body's response to infection, irritation or injury, which causes redness, swelling, pain and sometimes a feeling of heat in the affected area.

Content provided by NHS Choices www.nhs.uk and adapted for Ireland by the Health A-Z.

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