Infectious diseases in children: Scarlet Fever

Scarlet fever is a relatively common disease, but unlike many infectious diseases seen in children, is not vaccine preventable. Although nowadays it is seldom regarded as serious it remains a notifiable disease, and with the increasing problem of antibiotic resistance, there is no room for complacency

Scarlet fever, or scarlatina as it is sometimes known, is still quite a common condition in UK primary care, occurring in sporadic outbreaks particularly in winter and spring. It is an important cause of red rash, it can have complications, and it needs to be recognised at presentation as it is a notifiable disease. In 2009 there were over 4,000 case notifcations in England and Wales. There seem to be four-yearly resurgencies with evidence that we are currently heading into another resurgence.¹

HISTORY OF SCARLET FEVER

Scarlet fever is an old disease, first described by Hippocrates in 400 BC.^2,3

Over the last hundred years scarlet fever has become less severe — it used to be a deadly disease that struck fear into the hearts of parents. Early in the twentieth century quarantine signs were set up whenever scarlet fever erupted.

The fact that we now rarely see this 'malignant' scarlet fever is partly due to the availability of antibiotics, but also partly because the streptococcal toxins have changed over time and now produce a milder illness.

In the early to mid-twentieth century people began to call the new, milder and less dangerous scarlet fever, scarlatina. Now that the old dangerous form is no longer seen, the two names have become interchangeable.

THE ORGANISM

Scarlet fever is caused by infection with a group A Streptococcus, strep pyogenes, which produces toxins with systemic effects, including a vivid scarlet rash (hence the name). The primary site of infection is usually the tonsils, where it gives rise to a purulent tonsillitis, but scarlet fever can also occur occasionally, when the same organism takes root in the skin, as impetigo. The toxins are actually acquired by the bacteria when they themselves are infected by a type of virus called a bacteriophage.

Not all streptococci A bacteria make the toxin — and when the toxin is produced not everyone is sensitive to it. Two children in the same family may both have strep infections, but one child (who is sensitive to the toxin) may develop the rash of scarlet fever while the other may not.

WHO GETS IT?

Scarlet fever most commonly affects children under 10 as most children over this age have experienced a strep infection and have some immunity. However, it is also occasionally seen in older children and adults, particularly during outbreaks.

The term specifically refers to the syndrome of infection, which includes the scarlet rash. Presence of the bacteria without the rash is not scarlet fever.

Scarlet fever is a 'notifiable' disease, which means that doctors in England and Wales have a legal obligation to inform the 'Proper Officer' of the Local Authority of suspected cases.

SYMPTOMS

The rash is the most striking sign of scarlet fever.^4,5 This is a scarlet, confluent rash, mainly macular (flat) rather than papular (bumpy). It usually begins looking like a bad sunburn with tiny bumps and it may itch.

The rash usually appears first on the neck and face, often leaving a clear unaffected area around the mouth. It then spreads to the upper trunk and the rest of the body. In the body creases, especially around the axillae it forms red streaks called 'Pastia lines'. On very dark skin, the streaks just look dark.

The rash normally blanches dramatically on light pressure. By the sixth day of the infection it fades, and the affected skin may begin to peel, leading to confusion — at times — with Kawasaki disease in which peeling of the hands and feet classically occurs in conjunction with a florid migrating red rash. Peeling of scarlet fever can last over a week.

Aside from the rash, the most typical symptoms of scarlet fever are a florid tonsillitis with fever >38°, and swollen glands in the neck. There is pus on the tonsils (if tonsils are present — they usually are in florid cases) and the tongue may have a whitish or yellowish coating. There is classically a 'strawberry tongue', when the tongue is red —and often tender or sore — and the taste buds show up as white specks on it, giving a strawberry like appearance.

Patients feel shivery and achey, and nausea, vomiting, and loss of appetite are typical. The fever lasts 3-5 days, unlike a viral fever, and the sore throat also lasts about 5 days.

With antibiotic treatment, the infection itself is usually cured with a 10-day course of antibiotics, but it may take a few weeks for tonsils and swollen glands to return to normal.

In rare cases, scarlet fever may develop from a streptococcal skin infection rather then a throat infection. In these cases, the child may not get a sore throat, but may well have an area of impetigo.

COMPLICATIONS

Complications include sepsis due to localised or overwhelming bacterial infection, and various types of inflammation due to immune responses to the toxin.

Septic complications are fortunately rare, but include ear and sinus infection, pneumonia, meningitis and full-blown septicaemia (this was the malignant scarlet fever of old).

Immune complications include acute kidney inflammation (glomerulonephritis), which can lead to renal failure, rheumatic fever and arthritis. Hepatitis is also occasionally seen.

A further complication, now rarely seen was a secondary run of scarlatinous disease, called 'secondary malignant syndrome of scarlet fever', around 18 days into an untreated infection. This syndrome involves renewed fever, with recurrence or new occurrence of some or all of the complications listed above.

PREVENTION

Scarlet fever is highly contagious. It is spread by nasal droplet infection through the respiratory mucosa. It tends to spread rapidly through families, and through schools and nurseries, and prevention is still essentially by isolation.

There is no vaccine against scarlet fever. One was developed in 1924 but it had poor efficacy and the arrival of antibiotics made it defunct. Around 20% of school age children carry the bacteria asymptomatically so it is endemic in the community.

DIAGNOSIS

The rash and accompanying symptoms of scarlet fever are usually fairly clear, but the two particularly important differential diagnoses of rash in an ill child are Kawasaki disease and meningococcal disease. The latter normally, and famously, causes a purple non-blanching rash — but nor all children with meningococcal disease have purpuric rash — more than 10% have a red blanching rash at presentation. Both may have permanent or even fatal consequences.

Throat swabs can be used to confirm scarlet fever, and diagnosis is easier on the background of current outbreaks — but if any doubt remains as to the diagnosis then review in a paediatric ward to exclude the other very serious diagnoses should be considered.

Antigen detection kits are available, and allow quick diagnosis and hence more appropriate administration of antibiotics. However, the cost and variable sensitivity and specificity of these mean that use is limited in the NHS.

ANTIBIOTICS AND SCARLET FEVER

From circa 1900, horse serum (from immune horses) was used in the treatment of children and reduced mortality rates significantly.

The recommended treatment these days is a 10-day course of penicillin.⁶ In penicillin-allergic children, erythromycin is usually used.⁷ However, a strain of strep pyogenes resistant to erythromycin and other macrolides (though not penicillin) caused two deaths in Hong Kong in 2011. In Hong Kong 60% of infections are now erythromycin resistant.⁸

A note on penicillin allergy

Remember true penicillin allergy is very rare. Children are often believed to be allergic to it because they are given penicillin and then develop a rash. Often the rash is due to the underlying disease process. It's impossible to tell in retrospect, but this is an example of how important it is to avoid recording penicillin allergy in children's notes without a high level of certainty, as there are times in life when penicillin really does seem to be the best thing to give.

MANAGEMENT

Children with a nasty strep throat may need soft foods or a liquid diet as swallowing may be uncomfortable. It's necessary to increase fluid intake as much as possible, since the raised temperature will massively increase insensate fluid losses.

Cool-mist humidifiers or steam from hot water or a boiled kettle to add moisture to the air help to soothe a sore throat.

SCARLET FEVER IN FICTION

In a number of novels, scarlet fever has provided a convenient means of killing off unwanted characters, including Frankenstein's mother, and the owner of the Velveteen rabbit (whose toys, including the rabbit, must thus be burned).

CONCLUSION

Scarlet fever is an old disease that seems to have become mild. It is easy to become complacent. However, the deaths in Hong Kong in 2011, and emerging resistance to antibiotics across the world mean we cannot forget this disease, which once threatened the health — and lives — of our children. Scarlet fever should remain in the forefront of our minds when diagnosing sick children with rashes.

REFERENCES

1. Statutory Notifications of Infectious Diseases (NOIDs) - tables - England and Wales. Health Protection Agency http://www.hpa.org.uk/hpr/archives/2012/hpr5112.pdf accessed July 2013

2. Rolleston JD. The history of scarlet fever. Br Med J 1928;2: 926—9.

3. Radikas R, Connolly C. Young patients in a young nation: scarlet fever in early nineteenth century rural New England. Pediatr Nurs. 2007 Jan-Feb;33(1):53-5.

4. Scarlet fever information leaflet http://www.patient.co.uk/search.asp?searchterm=scarlet+fever&searchcoll=All&x=0&y=0 accessed July 2013

5. Mahajan VK, Sharma NL. Scarlet Fever. Indian Pediatr. 2005 Aug;42(8):829-30.

6. De Meyere M, Mervielde Y, Verschraegen G, et al. Effect of penicillin on the clinical course of streptococcal pharyngitis in general practice. Eur J Clin Pharmacol. 1992;43(6):581-5.

7. Aber C, Alvarez Connelly E, Schachner LA. Fever and rash in a child: when to worry? Pediatr Ann. 2007 Jan;36(1):30-8.

8. BBC news. Scarlet fever hits Hong Kong http://www.bbc.co.uk/news/health-13858115 accessed July 2013