Group A streptococcus, commonly abbreviated to GAS or Strep A, is a common bacterium often found on the skin or in the throat and usually causes no problems. However, there is an association with several infections, some mild, some more severe, the most serious of these caused by an invasive group of Strep A bacteria known as iGAS (UK Health Security Agency 2022). Whilst iGAS infections are still uncommon, there has been an increase in cases this year, particularly in children under 10 and sadly, these have resulted a small number of deaths (UK Health Security Agency 2022). The increased incidence is of concern to clinicians in General Practice and this article therefore hopes to give nurses and non-medical prescribers more information and increased confidence in recognising symptoms of concern and getting early treatment, and hopefully preventing more serious consequences.
Prevalence
Infections caused by Strep A typically come in waves and in previous years outbreaks have occurred around March to April (McKechnie 2022). However, in December 2022, there was a reported increase in the number of infections in the UK, resulting in deaths of young children, occurring as a result of invasive infections (UK Health Security Agency 2022). In particular, there has been a steep increase in scarlet fever and GP consultations for this disease, occurring early in the 2022 to 2023 season, and these have been greater than would be expected at this time of the year (GOV UK 2022). In children below the age of 10, the rate of iGAS infections has been substantially higher in the past 2 years, a problem currently under investigation following reports of an increase in lower respiratory tract and empyema Gas infections, (GOV UK 2023).
Mode of spread
Infection is spread in the same way as other viruses, either airborne by droplets (coughing sneezing etc) or by contact (from an infected wound for example). Infection is highly contagious and can be spread to others. Some people can have the bacteria present in their body without any symptoms at all, and while they can pass it on, the risk of spread is much less than is the case if the person is unwell (UK Health Security Agency 2022).
Infections caused by GAS (GOV.UK 2022)
The bacterium is potentially responsible for a for several infections affecting the skin, respiratory tract, and soft tissue.
The commonest of these are:
- Pharyngitis and tonsillitis
- Scarlet fever
- Impetigo
- Cellulitis
Signs and symptoms
Signs and symptoms will differ according to the site of the infection. These are as follows:
Pharyngitis and tonsillitis
Sore throat and throat infections are a common cause of visits to GP surgeries, and may be bacterial (most commonly streptococcus) or viral (typically rhinovirus) in origin (Kenealy 2014). Both viral and bacterial infection have similar symptoms which can make diagnosis more challenging. Viral sore throats may present with a very sore or painful throat making swallowing difficult, and in addition tonsils will be red and enlarged. Patients with tonsillitis due to strep A will have a fever, enlarged lymph nodes in the neck, and white or yellow spots on the tonsils (NHS Inform 2023a). Non-specific symptoms such as nausea vomiting and abdominal pain, may be present in children with pharyngitis and all people with tonsilitis, however rhinorrhoea, nasal congestion and cough are frequently present in viral pharyngitis but not in bacterial pharyngitis (NICE 2023). To help clinicians with decision making and guide treatment decisions, two useful guides have been developed to help diagnose the likelihood of Strep A infection. (see tables 1 and 2)
Table 1. (GP Notebook 2022a)
| Fever pain criteria | Yes | No | Evaluation of scores |
|---|---|---|---|
| Fever (during the previous 24 hours) | 1 | 0 | A score of 0 or 1 is thought to be associated with a 13 to 18% likelihood of isolating streptococcus |
| Purulence (pus on the tonsils) | 1 | 0 | A score of 2 or 3 is thought to be associated with a 34-40% likelihood of isolating streptococcus |
| Symptom onset less than 3 days | 1 | 0 | A score of 4 or 5 is though to be associated with a 62-65% likelihood of isolating streptococcus |
| Absence of cough or coryza | 1 | 0 | Higher scores suggest more severe symptoms and likely bacterial (streptococcal) cause |
| Severely inflamed tonsils | 1 | 0 |
Table 2. Centor criteria: (NICE 2023)
| Symptom | Score | Additional information |
|---|---|---|
| Tonsillar exudate | 1 | A score of 0, 1 or 2 is though to be associated with a 3 to 17% chance of isolating streptococcus |
| History of fever > 38 degrees | 1 | As above |
| Lymphadenitis or tender anterior cervical lymphadenopathy | 1 | A score of 3 or 4 is associated with a 32-56% likelihood of isolating streptococcus |
| Absence of cough | 1 | As above |
Scarlet fever
Incubation period is generally 2 to 5 days from initial exposure to Group A streptococcus before becoming unwell with the disease (UK Health Security Agency 2019). Risk of developing the illness is highest in the very young or the elderly, those with comorbidities (e.g., diabetes or cancer), drug or alcohol abusers and those who are immunocompromised (e.g., HIV) (NICE 2022). Scarlet fever is one of several notifiable diseases which must be reported to the health protection team, who must forward this to the UKHSA within 3 days of being notified or within 24 hours for urgent cases (UK Health Security Agency 2010).
Symptoms include: (Hazell 2022)
- High temperature
- Very red sore throat
- Swollen glands in the neck
- Bright red tongue (strawberry tongue)
- Bright red rash on the chest, abdomen and cheeks which usually appears 12-48 hours after the initial infection and has a sandpaper feel to it on examination.
Impetigo
Impetigo is a common, highly common skin infection characterised by pustules and honey-coloured crusted erosions, and although it can affect any age it is commonest in young children (Quirk 2022). The most common causative organism is staphylococcus aureus, and less commonly streptococcus pyogenes (Tidy 2020) Cellulitis: This is an acute bacterial infection of the skin and subcutaneous tissues, frequently caused by streptococci (Rehmus 2021). Patients present with redness and swelling of the affected area which is painful and feels warm to the touch.
Invasive GAS infections
Infections caused by invasive strep A are more concerning and are almost always treated in the hospital setting. More serious infections are more likely to occur in the elderly, the very young or those with an underlying health problem, such as drug addiction, alcoholism, cancer and the immunosuppressed (NHS Inform 2023b). The commonest of these are discussed below, rarer diseases are shown in are shown in Table 3.
Table 3. Invasive GAS infections: (Smith 2022, NHS Inform 2023b)
| Disease | Additional information |
| Toxic shock syndrome | This is a rare but life-threatening condition associated with fever, nausea, vomiting, diarrhoea, flu like symptoms, widespread rash, breathing problems and dizziness |
| Necrotising fasciitis | This is a rare life-threatening disease. Symptoms develop over hours or days and include severe pain and loss of feeling close to wound or laceration. This is accompanied by fever, swelling of the tissues of the affected area, headaches with later onset of mental confusion, sickness and diarrhoea and discoloured blotches on the skin (may be purple grey of black in colour) |
| Bacteraemia | Infection of the blood stream |
| Streptococcal toxic shock syndrome | Rapidly progression of symptoms with low blood pressure and multi organ failure |
| Meningitis | This occurs as a result of infection of the membranes surrounding the brain and spinal cord |
Pneumonia
Patients with pneumonia may present with a variety of symptoms, the most common of these include dyspnoea, cough, pleuritic pain, sputum production, and fever, however the elderly often present with a more complex clinical picture and may not display typical symptoms leading to delayed diagnosis and increased mortality rates. (Dion and Ashhurst 2022)
Septicaemia
This is a term used to describe blood poisoning. Symptoms include a high fever and rapid or shallow breathing (a medical emergency), and in some cases vomiting and diarrhoea. (Smith 2022)
Diagnosis
Diagnosis may be made on history and signs and symptoms, however GAS is formally diagnosed by microbiological culture of samples taken from the affected site (UK Health Security Agency 2014). Throat swabs do not usually play a significant role in the diagnosis of streptococcal sore throat, because its presence does not necessarily mean that it is the cause of a sore throat, and the results take some days to be available (Hazell 2022). Current guidance advises that a throat swab should be considered if there is ‘diagnostic uncertainty’ or concerns about antibiotic resistance, and drug sensitivities will be helpful in guiding the second choice of antibiotic if the first treatment has been ineffective (Hazell 2022).
Treatment
Most Strep A infections are easily treatment with antibiotics.
Guidance is as follows: (GP Notebook 2022b)
- Phenoxymethylpenicillin is first choice because of its effective, narrow spectrum of activity and lack of resistance to its use
- If availability is a problem or the person has a penicillin allergy, macrolides (erythromycin, clarithromycin or cefalexin) are an alternative.
- If the penicillin allergy is severe (history of anaphylaxis, respiratory distress, angioedema or urticaria), macrolides are the recommended choice, cotrimoxazole is an alternative if macrolides are unavailable.
- Evidence has suggested that both cefalexin and co-trimoxazole may increase the risk of antimicrobial resistance.
- A five-day course of antibiotics may be sufficient to achieve a cure but a 10-day course may be needed to ensure complete resolution.
Contacts
Parents of children diagnosed with strep A will need to know about duration of time of school or nursery. Guidance updated in December 2022 and again in February 2023 advises exclusion from school or nursery is required for 24 hours after starting antibiotics (UK Health Security Agency 2023). Prescribing for contacts of GAS infections is the domain of health protection teams who provide specialist support and will identify and give advice regarding prophylaxis (GP Notebook 2022c). A close contact is defined as prolonged contact with the case in a household-type setting during the 7 days before onset of symptoms and up to 24 hours starting antibiotic treatment (GP Notebook 2022c). More information is given in Table 4.
Table 4. Guidance on prophylaxis for contacts of GAS infections (GP Notebook 2022c)
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Complications
Once the initial infection has resolved there is a risk of delayed problems. These are discussed below.
Rheumatic fever
This occurs when the strep A infections triggers and autoimmune response, leading to inflammation of the heart, joints and nerves (McKechnie 2022). This disease is rare in the UK and developed countries, but is still evident in some countries such as parts of Asia and the South pacific, the middle east and sub-Saharan Africa.
Post streptococcal glomerulonephritis
This characteristically occurs approximately 7 to 14 days after infection with group A beta haemolytic streptococcus, and is estimated to accounts for 90% of acute glomerulonephritis (GP Notebook 2018). The problem can occur at any age but most commonly occurs in the under-fives and has a good prognosis with eGFR usually returning to normal within 10 to 14 days and 92% and 98% of patients recovering completely. (GP Notebook 2018)
Paediatric autoimmune neuropsychiatric disorders
These disorders are associated with streptococcal infections (PANDAS) and describe a condition where children suddenly develop symptoms of obsessive-compulsive disorder and mental health problems, although the association remains unproven scientifically. (Tan et al 2012)
In summary
Because of the ease of spread of Strep A infection, hand hygiene is key to preventing transmission to others. Guidance also advises avoidance of close contact with anyone unwell, using a tissue to cover the mouth and nose if coughing and dispose of used tissues as soon as possible (NHS 2022). For clinicians assessing patients, criteria to guide decision making has been discussed (see tables 1 and 2) with throat swabs an option if the diagnosis remains in doubt.
Conclusion
Strep A infections are common and are rarely serious but in 2022 there was a rise in the number of cases which resulted in a small number of deaths. Patients affected may have a mild illness, or in some cases its impact may be more severe leading to hospital admission and a potentially serious outcome. Nurses who run minor illness clinics may well see cases in their clinics. This article has therefore hoped to increase knowledge among nurses and non-medical prescribers in recognising and treating strep A infections so that those affected can make a speedy recovery with appropriate treatment and management and a reduction in more severe outcomes.
KEY POINTS
- Cause several infections frequently affecting the throat and skin
- Usually harmless but in rare cases can become invasive causing more serious disease
- If treatable in the community antibiotics are usually prescribed for 10 days to ensure resolution of the infection
- Invasive infections are almost always treated in hospital