Cases of scarlet fever are on the rise again and reached a 50-year high in England in 2016, researchers have warned.
After decades of declining incidence, England experienced an unprecedented rise in scarlet fever in 2014, with a seven-fold increase in new cases notified in the five years between 2011 and 2016.
“The magnitude of the recent upsurge is greater than any documented in the last century”
A total of 620 outbreaks – representing over 190,00 cases – of the 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, according to research published in The Lancet Infectious Diseases journal.
Several countries in East Asia have also reported an escalation, including Vietnam, China, South Korea, and Hong Kong.
Whilst not usually serious, patients will require antibiotic treatment to reduce the risk of complications, as well as to reduce the likelihood of the infection being passed on to others.
As it is highly contagious, anyone diagnosed with scarlet fever should be advised to stay at home until at least 24 hours after the start of antibiotic treatment to avoid passing on the infection.
However, around one in 40 cases are admitted to hospital, although just over half are discharged the same day, noted the authors of the study from the national agency Public Health England.
“The hunt for further explanations for the rise in scarlet fever goes on”
The authors asked for awareness 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, they added.
The researchers admitted that the reason for the ongoing rise in cases remained unidentified, though genetic testing had ruled out a newly-emerged, more virulent strain of the infection.
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.
Typically, natural cyclical patterns of scarlet fever incidence occur every four to six years. A common cause of childhood death in the 1800s, it has become less common and milder over the past century.
But, following an unusually high number of cases noted in England in 2014, public health authorities from across the UK joined forces to investigate the sudden increase.
- Nurses told to be on lookout for potential cases of scarlet fever
- High scarlet fever levels expected for third consecutive year
- Guidance to tackle ‘extraordinary rise’ in scarlet fever
The researchers analysed statutory scarlet fever notifications from 1911 onwards in England and Wales, as well as examining samples taken from throat swabs collected across England in 2014.
The findings showed 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, hospital admissions almost doubled between 2013 (703 cases) and 2016 (1,300).
All areas of England experienced a marked increase in notifications in 2014, with 87% in children under 10 years old, noted the researchers.
The highest infection rates in 2015 and 2016 were recorded in the East Midlands, Yorkshire and Humber, and North East regions.
Unexplained resurgence of scarlet fever cases across England
Source: Group B Strep Support
Surprisingly, analysis of strains revealed that the increase was not caused by spread of a single scarlet fever-causing GAS strain, said the researchers.
Instead, a genetically diverse range of established strain types were identified, with 43% of isolates being emm3, 15% being emm12, 11% being emm1, and 1% comprising emm4.
Lead study author Dr Theresa Lamagni, head of Streptococcal surveillance at Public Health England, said: “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.
“Whilst notifications so far for 2017 suggest a slight decrease in numbers, we continue to monitor the situation carefully,” said Dr Lamagni.
“Guidance on management of outbreaks in schools and nurseries has just been updated and research continues to further investigate the rise,” she said.
Dr Lamagni added: “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.”
“Heightened global surveillance for the dissemination of scarlet fever is warranted”
Mark Walker and Stephan Brouwer
Writing in a linked comment in the same journal, Australian academics noted that there were several hypotheses for triggers behind the scarlet fever epidemics.
These included the acquisition of scarlet fever-causing genes by the bacteria, changes in human immune status, environmental change, or an unknown agent that predisposed the host to disease.
Professor Mark Walker and Stephan Brouwer, from the University of Queensland, said: “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,” they added.