Strep A and scarlet fever: What pharmacists should know and advise

Scarlet fever is an infectious disease caused by bacteria called streptococcus pyogenes, or group A streptococcus (GAS).

The same bacteria can also cause other infections such as cellulitis, sore throat and impetigo. Scarlet fever is characterised by a rash, which usually accompanies a sore throat.

GAS produces toxins, which cause the characteristic sandpaper red rash (the “scarlet” of scarlet fever), a red and swollen tongue, and flushed cheeks.

Scarlet fever mainly affects children between two and eight years old, with around 90% of cases occurring in children under 10. It is highly contagious.

It is spread by close contact with an infected carrier through respiratory droplets and direct contact. Rarely, it is spread through food that is not handled properly.

What is the difference between scarlet fever and group A strep?

GAS, which causes scarlet fever, can enter the bloodstream resulting in an invasive group A streptococcus (iGAS) infection. This can be severe and life-threatening, requiring urgent referral and management to secondary care.

iGAS is an infection where the bacteria is isolated from a normally sterile body site, such as the blood, joints or the lungs. The terms scarlet fever and iGAS refer to two infections caused by the same bacteria.

Scarlet fever and iGAS are notifiable diseases. All cases must be reported to the UK Health and Security Agency to enable contact tracing and safety netting of contacts of anyone who has been infected with the highly transmissible bacteria.

Symptoms

The first symptoms of scarlet fever often include a sore throat, headache, fever, nausea and vomiting. It usually takes two to five days from infection before the first symptoms appear. However, the incubation period may be as short as one day and as long as seven days.

After 12 to 48 hours the characteristic fine red, ‘sandpaper’ rash develops, typically first appearing on the chest and stomach, rapidly spreading to other parts of the body.

On more darkly-pigmented skin, the rash may be harder to spot, although the ‘sandpaper’ feel should be present.

Further symptoms include:

fever over 38.3º C (101º F) or higher
white coating on the tongue, which peels a few days later, leaving the tongue looking red and swollen (known as ‘strawberry tongue’)
swollen glands in the neck
feeling tired and unwell
a flushed red face, but pale around the mouth. The flushed face may appear more ‘sunburnt’ on darker skin
peeling skin on the fingertips, toes and groin area, as the rash fades.

Co-circulating influenza or chickenpox

Children who have recently had chickenpox, which is caused by varicella-zoster virus (VZV), or influenza are at increased risk of complications of scarlet fever.

Parents are advised to be vigilant for signs of complication. In the case of chickenpox co-circulation, children in the setting who have not previously had chickenpox or the VZV vaccine will be offered the vaccine.

There is no evidence that offering the influenza vaccine in this situation is beneficial.

Diagnosis

Scarlet fever can be diagnosed on the classic symptoms alone in many cases, a throat swab will be sent for laboratory confirmation and to test antimicrobial sensitivity.

In this current season all laboratory isolates of GAS are universally susceptible to penicillin, meaning antibiotic treatment with phenoxymethylpenicillin or penicillin V should successfully treat scarlet fever if initiated promptly.

Treatment

Although mild cases of the disease may resolve on their own, it should be treated with antibiotics. Antibiotics reduce the risk of complications and reduce transmission.

The usual treatment is 10 days of penicillin or a suitable alternative where this is an allergy.

Given the current high prevalence of GAS, and the increased likelihood of GAS as cause of sore throat in children, the updated recommendation to prescribe antibiotics to children can be found here.

Antibiotic shortages

If there are problems sourcing liquid antibiotics, arrangements should be made with the prescriber to ensure the course is started without delay with tablets.

More help and advice on giving children tablets can be found on Specialist Pharmacist Service website.

In the event of non-availability, amoxicillin, macrolides and cefalexin are alternative agents in decreasing preference.

Macrolides and cefalexin are options of choice in non-severe penicillin allergy. In severe penicillin allergy, macrolides remain the option of choice.

Additional advice

Drink plenty of fluids to prevent dehydration
Regular paracetamol or ibuprofen to reduce fever
Be vigilant for any signs of complications in individuals with scarlet fever and of symptoms in other household members. Maintain a low threshold for considering pulmonary complications of GAS, especially:

○ if presenting with an illness compatible with bacterial pneumonia, and concurrent or

○ recent scarlet fever, or GAS infection or the patient was recently in contact with a case of scarlet fever/GAS infection. Prompt initiation of appropriate antibiotics remains key.

Prevent spreading

Scarlet fever is spread via the mucus and saliva of infected people. Parents and children should be advised to:

Wash hands regularly with soap and water for at least 20 seconds
Avoid sharing of cutlery, plates and glassware
Cough and sneeze into a tissue, disposing and washing hands
Follow advice regarding exclusion from group settings, schools and nurseries for at least 24 hours after antibiotics have been commenced or after the resolution of symptoms where antibiotics have been refused.

Health protection teams will identify contacts and advise on the requirement of antibiotic prophylaxis.

Orlagh McGarrity is an infection pharmacist at Great Ormond Street Hospital and Fan Cheng is research fellow at NIHR Clinical Research Network