Media ReleaseFrom: The Lancet
Resurgence of scarlet fever across England, but the underlying cause remains elusive
Cases of scarlet fever reached a 50-year high in England in 2016. Several countries in East Asia have also reported an escalation, including Vietnam, China, South Korea, and Hong Kong
After decades of declining incidence, in 2014 England experienced an unprecedented rise in scarlet fever, with a 7-fold increase in new cases notified in the last 5 years (2011-2016), according to research published in The Lancet Infectious Diseases journal.
A total of 620 outbreaks (over 19000 cases) of this highly contagious bacterial illness were reported in 2016, mostly in schools and nurseries. The population rate in 2016 was 33.2 cases per 100,000.
Whilst not usually serious, individuals should see their GP promptly as they will require antibiotic treatment to reduce the risk of complications. Antibiotic treatment also reduces the likelihood of the infection being passed on to others. Around 1 in 40 cases are admitted to hospital, although just over half are discharged the same day. The authors ask the public to be aware of the symptoms of scarlet fever, which include a sore throat, headache and fever accompanied by a characteristic pink-red rash that feels like sandpaper. Most cases occur in children under 10 although individuals of any age can develop the condition.
The reason for this ongoing rise in cases remains unidentified. Molecular genetic testing has ruled out a newly emerged strain of the infection with increased ability to spread between individuals. Research is underway to understand the possible cause and assess prevention strategies.
“Whilst current rates are nowhere near those seen in the early 1900s, the magnitude of the recent upsurge is greater than any documented in the last century,” says Dr Theresa Lamagni, Head of Streptococcal Surveillance at Public Health England, London, UK who led the study. “Whilst notifications so far for 2017 suggest a slight decrease in numbers, we continue to monitor the situation carefully. Guidance on management of outbreaks in schools and nurseries has just been updated and research continues to further investigate the rise. We encourage parents to be aware of the symptoms of scarlet fever and to contact their GP if they think their child might have it.” 
Scarlet fever is caused by bacteria known as Streptococcus pyogenes or group A Streptococcus (GAS), found on the skin and throat. Cases occur year-round but more commonly in the spring. It is spread through close contact with individuals carrying the organism or with objects and surfaces contaminated with GAS bacteria. Typically, natural cyclical patterns of scarlet fever incidence occur every 4 to 6 years. A common cause of childhood death in the 1800s, it has become less common and milder over the past century. Today scarlet fever can be treated with antibiotics, but in rare cases the bacteria can cause severe illnesses such as pneumonia, sepsis, and liver and kidney damage.
Over the past 5 years, several countries in East Asia have also reported an escalation, including Vietnam, China, South Korea, and Hong Kong.
Following an unusually high number of cases noted in England in 2014, public health authorities from across the UK joined forces to investigate the rise. In this study, researchers analysed statutory scarlet fever notifications from 1911 onwards in England and Wales , comparing the characteristics of cases (e.g., frequency of complications and hospitalisations) and outbreaks to pre-upsurge periods. They also examined the genetic properties of a sample of GAS isolates (303) from throat swabs collected from across England in 2014.
The findings show that incidence of scarlet fever tripled between 2013 and 2014, rising from 8.2 per 100,000 (4,700 cases) to 27.2 per 100,000 (15,637). Rapidly rising infection rates in 2015 (30.6 per 100,000) and 2016 (33.2), resulted in the highest rate and number of people notified (19,206) since 1967. Following the sharp rise in the absolute number of cases, hospitalisations almost doubled between 2013 (703 cases) and 2016 (1300).
All areas of England experienced a marked increase in notifications in 2014, with the majority (87%) in children under 10 years old. The highest infection rates in 2015 and 2016 were recorded in the East Midlands, Yorkshire & Humber, and North East.
Surprisingly, analysis of strains revealed that the increase was not caused by spread of a single scarlet fever-causing GAS strain. Instead, a genetically diverse range of established strain types (emm) were identified including emm3 (43% of isolates), emm12 (15%), emm1 (11%), and emm4 (1%). Genetic elements detected in Hong Kong were also found in emm12 strains in the UK, although only in a minority of isolates.
Dr Lamagni says, “Whilst there is no clear connection between the situation in the UK and East Asia, a link cannot be excluded without better understanding of the drivers behind these changes. The hunt for further explanations for the rise in scarlet fever goes on.”
A further independent evaluation of the number of GP consultations for scarlet fever confirmed this increase. However, the data suggest underreporting, with total scarlet fever cases notifications (15,637) representing only around half all GP consultations (26,500) nationwide in 2014.
Public Health England encourages prompt notification of cases and outbreaks to local health protection teams. As it is highly contagious, anyone diagnosed with scarlet fever is advised to stay at home until at least 24 hours after the start of antibiotic treatment to avoid passing on the infection. 
Writing in a linked Comment, Professor Mark Walker and Stephan Brouwer from the University of Queensland in Australia discuss potential triggers of the scarlet fever epidemics, saying that: “Hypotheses that have been proposed include acquisition of scarlet fever-causing genes into the S pyogenes population, changes in immune status in the human population, environmental change, and an as yet unknown and potentially novel co-infective agent that predisposes the host to disease. Further research needs to be done to better understand the causes of scarlet fever resurgence. Scarlet fever epidemics have yet to abate in the UK and northeast Asia. Thus, heightened global surveillance for the dissemination of scarlet fever is warranted.”
NOTES TO EDITORS
The study was funded by Public Health England.
 Quotes direct from author and cannot be found in text of Article.
 Scarlet fever is a notifiable disease in England, meaning that health professionals must report cases in their area.