Scarlet fever cases in England highest in 50 years

"Scarlet fever cases hit 50-year high in England," BBC News reports, as the childhood disease makes a puzzling return.

A study of the disease found an unexpected sharp rise in cases in 2014. Up until that year, the number of scarlet fever cases in England had massively declined over the past century.

Up until 2013, cases were at a low of around 3 to 8 cases for every 100,000 people. However, in 2014 this suddenly shot up to 27 per 100,000, reaching 33 per 100,000 in 2016.

Researchers suggest there may be a link with a similar surge of the disease in several countries in east Asia since 2009.

However, no other European country has experienced a similar rise in cases, which you might expect if strains were spreading from Asia.

Scarlet fever is a bacterial infection caused by group A streptococcus and mainly affects young children. It tends to cause sore throat and feverish symptoms, followed by a characteristic blotchy pink-red rash on the body. It is not normally serious but it does require prompt treatment with antibiotics to reduce the risk of more serious complications.

You should see your GP or call NHS 111 as soon as possible if you think your child has scarlet fever. Read more information about scarlet fever.

Where does the study come from?

The study was conducted by research teams from the National Infection Service, Public Health England (PHE); National Institute for Health Research Health Protection Research Unit in Healthcare-Associated Infection & Antimicrobial Resistance at Imperial College, London; Guy's & St Thomas' NHS Foundation Trust, and other institutions in the UK. No sources of financial support were reported.

It was printed in the peer-reviewed journal The Lancet: Infectious Diseases.

Most of the UK media's reporting of the study is accurate. However, The Mail Online's use of the phrase "deadly scarlet fever" is needlessly alarmist. Scarlet fever may have been deadly over 100 years ago due to a combination of widespread child malnutrition and a lack of antibiotics, but this is no longer the case.

It is very rare for scarlet fever to cause serious complications. Most cases are mild and can be treated effectively with antibiotics.

What kind of research was this?

This was a population-based cross-sectional study that looked at cases of scarlet fever across England and Wales from 1911 to 2016.

There has been a massive decline in rates of life-threatening infectious disease since the first part of the last century, largely due to improved hygiene, nutrition, living standards and healthcare. Scarlet fever was once a common cause of death, but when antibiotics came in cases declined sharply.

However, it's still a notifiable infection (meaning doctors should report cases to health authorities), and a sudden peak was recorded in 2014.

This study presents the collaborative effort by public health authorities in England to investigate the 2014 surge and possible reasons behind it.

What did the study do?

Doctors have to notify PHE Health Protection Teams of individual suspected cases of scarlet fever or outbreaks (two or more linked cases within a 10 day period). This was used as the source of data from 1997 to 2016.

For the period 1912 to 1997 scarlet fever notifications were collected by the Office for National Statistics and supplied to PHE's predecessor organisation the Public Health Laboratory Service. A single Medical Research Council report gave cases for 1911.

Up to 1982 they simply had data on the number of cases, and after that information on individual cases. Researchers looked at data on hospital admissions and discharges, any complications or deaths, and laboratory data on the cultured bacteria.

What were the basic results?

There was a sharp decline in scarlet fever cases and associated deaths throughout the 1900s. Between 1999 and 2013 there were about 3 to 8 notifications per 100,000 of the population.

However, there was a sudden rise in 2014. In about January/February 2014 there was a peak of 1,075 cases reported in one week, with 15,637 reports made over the course of that year. This was a rate of 27 per 100,000 – three times the rate of the previous year.

Rates continued to rise in the following years. In 2015 there were 17,696 notifications at a rate of nearly 31 per 100,000 rising to 33 per 100,000 in 2016. This was the highest recorded number seen since 1967.

Analysis of general practice data showed 26,500 GP consultations for scarlet fever in 2014, twice the rate of 2013. Further analysis showed the majority (87%) were in children aged less than 10 years – though notifications did span the age range 0 to 90. There was also an equal spread of cases boys to girls.

There was no geographical pattern to cases and they were spread across the country – though there were peaks in 2015 in the East Midlands (44 per 100,000) and Yorkshire and Humber (49 per 100,000).

One in 40 cases was admitted to hospital. Complications of infection occurred in less than 1% of all cases. These included isolated cases of pneumonia, tonsillar abscess and skin infection (cellulitis). There were no deaths.

Analysis across the past century shows a general cyclical pattern to cases reaching peak epidemics about every four years. However, they have been at much lower magnitudes in recent times. In 2011 the number of cases was so low that the rise from 2014 has been quite an upsurge.

What do the researchers conclude?

The researchers conclude: “England is experiencing an unprecedented rise in scarlet fever with the highest incidence for nearly 50 years. Reasons for this escalation are unclear and identifying these remains a public health priority.”

Conclusions

This valuable UK study gathers national data on the number of scarlet fever notifications each year from 1911 to 2016, and explores the characteristics around the rather dramatic increase since 2014.

It's useful to note that scarlet fever, like many infectious diseases, moves in cycles, with peaks and troughs. What it can't easily tell us is the reason why there should have been such a massive surge in cases since 2014, which does not seem to follow the natural cycle.

The researchers say that no other European country has experienced a sudden rise, though there was similar escalation in areas of Asia between 2009 and 2015. They say that there is no clear link between the two situations, though a link cannot be fully excluded at this stage. Laboratory analysis has also shown that these are not newly emergent bacterial strains.

Therefore, though this is a definite rise in cases we don't currently know the reasons. There may be some reassurance to know that, despite the higher number of cases, complications have been very rare and there have been no deaths.