Cause of England's Scarlet Fever Epidemic Remains a Mystery

Scarlet fever, once common in England and Wales in the mid-nineteenth century, has recently resurged in England. Now, in a new study, Public Health England researchers have sought to find out the cause of the biggest increase in scarlet fever cases England has seen in several decades.

Scarlet fever is an illness caused by Streptococcus pyogenes bacteria, or Group A Streptococcus, and gets its name from the telltale red rash that often occurs as a result of the infection. Other symptoms can include a very red, sore throat, high fever, headache, body aches, a red and bumpy tongue, and bright red skin in the creases of the underarm, elbow, and groin. Individuals who carry Group A strep in their nose or throat can spread the bacteria through their coughs and sneezes, and by sharing drinking glasses and eating utensils. Scarlet fever is also contagious through contact with skin sores and rashes but can be treated with antibiotics.

During the mid-1800s, pandemic outbreaks of scarlet fever in England caused a sharp rise in mortality. Improvements in hygiene and the development of antibiotics have since made scarlet fever a much less common and much more treatable infectious disease. From 1999 to 2013, England saw from 3 to 8 cases of scarlet fever per 100,000 individuals, resulting in 1,600 to 4,700 cases each year. Since 2014, however, England’s National Health Service (NHS) says that the country has been experiencing its biggest resurgence of scarlet fever in 50 years. Earlier that year, England saw a peak of 1,075 cases in just one week, and by the end of the year, 15,637 cases had been reported. Now in a new study, researchers from Public Health England (PHE) are trying to figure out why.

In the new study, published in the journal The Lancet Infectious Diseases, the authors write that rates of the illness in England tripled to more than 27 cases per 100,000 individuals from 2013 to 2014, with 87% of those cases occurring in children under the age of 10. In 2015, the rate of infection rose to more than 30 cases per 100,000 and in 2016 rose again to more than 33 cases per 100,000. The 19,206 cases of scarlet fever reported in England last year marks the highest number of cases to be reported there since 1967.

To identify possible causes, the study’s authors investigated clinical and epidemiological patterns. However, following whole-genome sequencing of clinical isolates, they found no novel lineage or genetic feature to explain the recent epidemic. Researchers have also failed to pinpoint any other forces that may be contributing to the population’s increase in susceptibility to scarlet fever or the disease’s capacity spread. In other words, the reason for the recent outbreaks is still a mystery.

“To our knowledge, England is the first western hemisphere country to describe an upsurge in scarlet fever incidence after reports in several countries in east Asia,” the authors wrote in their paper, noting that countries such as Vietnam, South Korea, Hong Kong, and mainland China have also seen rising scarlet fever incidence in recent years. “Comparison with historical UK data showed that the magnitude of the recent upsurge in scarlet fever was unique, suggesting the current phenomenon is not explained by the usual cyclical patterns in disease incidence.”

Concluding that a still unknown, but exceptional cause has been driving the recent outbreaks of scarlet fever, the authors stress that public health officials need more research to understand why they’ve been occurring. In the meantime, PHE has recently updated their guidelines for managing outbreaks in schools and nurseries, due to the fact that of the 1,070 outbreaks of scarlet fever that occurred in England in 2015 and 2016, the majority impacted young children—710 were in schools and 336 were in nurseries. With this updated guidance, PHE strives to better control these outbreaks and minimize their impact on public health.