Strep A is a group of bacteria that are a common cause of infection in humans. The bacteria can be spread in several ways.

Most infections are minor and 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.

Read more about the causes of throat infection.

Impetigo

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.

Read more about the causes of impetigo.

Cellulitis

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

Read more about the causes of cellulitis.

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.

Read more about the causes of otitis media.

Sinusitis

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

Read more about the causes of sinusitis.

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 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, known as a late-onset group B strep infection.

In most cases there is no obvious reason why this happens but known risk factors include:

• being born prematurely
• being part of a multiple birth – for example, twins or triplets
• having a mother with a history of group B strep infection

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

Streptococcal infections are any type of infection caused by the Streptococcus (‘strep’) group of bacteria.

There are many different types of Streptococci and infections vary in severity from mild throat infections to pneumonia. Streptococcal infections are usually treated with antibiotics.

Streptococci are divided into two key groups:

• alpha-haemolytic – made up of two groups, Streptococcus pneumoniae and Viridans Streptococci
• beta-haemolytic – made up of Group A and Group B Streptococci

This topic focuses on the beta-haemolytic group of Streptococci. Read about pneumococcal infections for information on infections caused by Streptococcus pneumoniae.

Group A and Group B strep

Group A strep (strep A) are often found on the surface of the skin and inside the throat. They are a common cause of infection in adults and children.

Group B strep (strep B) usually live harmlessly inside the digestive system and, in women, the vagina. Strep B tend to only affect newborn babies and usually cause more serious types of infection.

These two groups are described in more detail below. You can find information on the symptoms, causes and treatment of specific infections by following the links provided.

Strep A

Minor strep A infections

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

• a throat infection at the back of the throat, known as pharyngitis, which can cause swollen glands and discomfort when swallowing
• impetigo – a skin infection which can cause blistering of the skin around the nose, mouth, arms, trunk or legs
• cellulitis – an infection of the deeper layers of the skin, which most commonly affects the legs
• a middle ear infection, which often causes earache, a high temperature and some temporary hearing loss
• sinusitis – an infection of the small cavities behind the forehead and cheekbones, which causes a blocked or runny nose and a throbbing pain in your face

Invasive 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 infections include:

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

Diagnosing a strep A infection

Strep A infection can be diagnosed by taking a swab of affected tissue or saliva and checking it for the presence of bacteria. A blood test can also be used later on in the illness to check if your immune system has produced certain antibodies in response to a strep A infection.

If an invasive group A infection is suspected, blood tests can be used to confirm whether there are actually bacteria in the blood, rather than just the antibodies.

Who is at risk of a strep A infection?

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

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

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 England. They usually affect people with a weakened immune system, such as:

• 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
• pregnant women

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

Treating a minor strep A infection

Some minor strep A infections, such as a throat infection or inner ear infection, will often get better on their own without the need for treatment. 

Paracetamol or  non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen may be used to control any pain and fever. However, there is some evidence to suggest that NSAIDs can increase the risk of an invasive infection. This may be due to NSAIDs masking more severe symptoms, or delaying the immune system’s response to infection.

Aspirin should not be given to children aged under 16.

Minor infections of the skin will usually require treatment with antibiotic tablets or creams.

Most people with a minor strep A infection will make a full recovery and experience no long-term complications.

Treating an invasive strep A infection

Invasive strep A infections (with the possible exception of pneumonia) are regarded as a medical emergency and you’ll need to be admitted to hospital. You may need to be placed in an intensive care unit while medical staff treat the infection.

The infection is usually treated with injections of antibiotics for 7-10 days. In some cases, surgery may be needed to remove or repair damaged tissue. Occasionally, a blood transfusion may be used to help neutralise toxins produced by the bacteria.

The outlook for more serious invasive strep A infections 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.

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.

Strep B in pregnancy

It is estimated that 1 in 5 pregnant women have strep B bacteria in their vagina and/or digestive system. The bacteria can sometimes be passed on to the baby through the amniotic fluid (a clear liquid that surrounds and protects the unborn baby in the womb). Strep B infections are thought to affect 1 in every 2,000 births.

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

Strep B in newborn babies

The symptoms of a strep B infection in a newborn baby usually develop within the first 12 hours of giving birth and 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

In some cases a baby can catch an infection a few months after birth, known as a late-onset group B strep infection. There is often no obvious reason why this happens, but known risk factors include:

• being born prematurely
• being part of a multiple birth – for example, twins or triplets
• having a mother with a history of group B strep infection

Treating a strep B infection

As newborn babies have a poorly developed immune system, the bacteria can quickly spread through their body, causing serious infections such as meningitis and pneumonia.

Healthcare professionals take a preventative approach to treating strep B infections by trying to identify babies at high risk of developing such infections and giving injections of antibiotics (intravenous antibiotics) to the mother during labour. Alternatively, the baby can be given intravenous antibiotics shortly after birth.

Known risk factors that may mean you need injections of antibiotics during labour include:

• you have previously given birth to a baby with a strep B infection
• strep B is found in your urine during tests carried out for other purposes
• strep B is found during vaginal and rectal swabs carried out for other purposes
• you have a high temperature during labour
• you go into labour prematurely

The preventative approach is used because although survival rates have improved significantly in recent years, 1 in every 10 babies with a strep B infection will die.

If your baby has symptoms that suggest a strep B infection, a diagnosis can be confirmed using blood and urine tests and they will need to be treated with intravenous antibiotics.

Strep bacteria can be prevented from spreading  by good hygiene.

This includes regularly washing your hands with soap:

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

Read more information on how to prevent germs spreading.

It is also important to make sure your hands are clean when handling young babies (less than three months old).

The group B strep bacteria, as well as other types of bacteria, live on the skin and young babies are more vulnerable to the effects of infection as they have an underdeveloped immune system.

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

Read more about treating cuts and grazes.

If you have a streptococcal infection, your symptoms will depend on the type of infection you have.

Symptoms of strep A infections

Usually, strep A infections only cause minor symptoms. Only in rare cases can a more serious infection develop.

Throat infection

Symptoms and signs of a sore throat include:

• swollen tonsils
• swollen glands in your neck
• a painful, tender feeling at the back of your throat
• discomfort when swallowing

Read more about the symptoms of a throat infection.

Skin infections

The two most common strep A skin infections are:

• Impetigo – red sores or blisters develop, usually around the nose and mouth or on the arms, trunk or legs. The sores usually burst soon after they appear, leaving thick, golden crusts. The crusts dry to leave a red mark that will usually heal without scarring. Impetigo is not painful, but can make skin feel very itchy.
• Cellulitis – this most commonly affects one of your legs but symptoms can develop in any area of your body. Cellulitis causes the skin to become red, painful, hot, swollen and tender. Blisters may also develop on your skin. You may feel generally unwell, with a high temperature, nausea, shivering and chills.

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

Read more about the symptoms of inner ear infection.

Sinusitis

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

Read more about the symptoms of sinusitis.

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, causing 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 deep layer of skin that causes the affected tissue to die (gangrene)

Symptoms of strep B infections

Strep B infection usually only affects newborn babies, but it can spread quickly and cause serious infections.

The symptoms of a strep B infection in a newborn baby usually develop within the first 12 hours of giving birth. Typical signs in the baby are:

• 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.

Treatment for a streptococcal infection will vary depending on whether it is a minor or invasive strep A infection, or a strep B infection in a newborn baby.

Minor strep A infections will often clear up on their own. In some cases, your GP may prescribe a short course of antibiotics.

Invasive strep A infections and strep B infections can be much more serious and require emergency treatment with injections of antibiotics.

These treatments are described in more detail below.

Minor strep A infections

Throat infection

To help relieve symptoms:

• 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

Paracetamol or non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen may be used to control any pain and fever. However, there is some evidence to suggest that NSAIDs can increase the risk of an invasive infection. This may be due to NSAIDs masking more severe symptoms, or delaying the immune system’s response to infection.

Antibiotics are not recommended for throat infections since most are due to viruses, not streptococcal infections. Antibiotics 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 circumstances, 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.

Read more about the treatment of throat infections.

Skin infections

Impetigo can be treated using antibiotic cream.

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

Read more about the treatment of impetigo and cellulitis.

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 younger than 16.

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

Read more about the treatment of otitis media.

Sinusitis

If your symptoms of sinusitis do not resolve within seven days your GP will often prescribe 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.

Read more about the treatment of sinusitis.

Invasive infection

Invasive strep A infections (with the possible exception of pneumonia) are regarded 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 help support any affected body function, such as breathing or blood circulation, while medical staff will 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 7 to 10 days.

If there is an identifiable source of infection, such as an infected wound, it has to be treated. 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 injections of antibiotics (intravenous antibiotics) during labour.

Alternatively, the baby can be given antibiotics shortly after birth.

Known risk factors that may mean you need to have injections of antibiotics during labour include:

• having given birth to a previous baby with a strep B infection
• if strep B is found in your urine during urine tests 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 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.