After more than a decade of decline and flat numbers, the incidence of Scarlet Fever began rising dramatically in 2013 in the UK (see chart above), and for the fifth year running they are reporting rising numbers with an even earlier start to the season than usual.
Scarlet Fever primarily affects children under the age of 12, although adults can be affected. It is highly contagious, and while there is no vaccine, antibiotics are generally effective when treated early.
Scarlet fever (Group A Streptococcus or GAS) is caused by the bacterium Streptococcus pyogenes - which like viruses, can evolve over time – sometimes resulting in increased virulence, greater transmissibility, and/or antibiotic resistance.
Strains are identified by changes in their M-protein gene sequence (emm types) – which often determines virulence - and within these types new variants can emerge.Although less common, a more serious yet related illness is called iGAS (invasive Group A Strep), which indicates infection of the bloodstream, deep tissues, or lungs, and may result in severe (and frequently fatal) cases of necrotizing fasciitis and streptococcal toxic shock syndrome.
While also caused by the same Streptococcus pyogenes bacteria, iGAS can strike any age, with those over 65 most commonly affected.
And this year, PHE reports iGAS cases are also rising sharply (see chart below), running 26% higher for this time of the year than the average over the past 5 years.
Some excerpts from today's report follow:
Group A streptococcal infections: first report on seasonal activity in England, 2017/18
Health Protection Report Advanced Access report
Volume 12 Number 5
9 February 2018
Early indications suggest the 2017/18 scarlet fever season will be the fifth elevated season in a row. Current weekly notifications are higher than those reported at this point in the last four seasons (weeks 37 to 04, 2013/14 to 2016/17) . GPs, microbiologists and paediatricians are reminded of the importance of prompt notification of cases and outbreaks to local Public Health England (PHE) Health Protection Teams (HPTs), obtaining throat swabs (prior to commencing antibiotics) when there is uncertainty about the diagnosis, and exclusion of cases from school/work until 24 hours of antibiotic treatment has been received . The numbers of laboratory notifications of invasive group A streptococcal (iGAS) disease are also elevated compared to this point last season.
Due to rare but potentially severe complications associated with GAS infections, clinicians and HPTs should continue to be mindful of potential increases in invasive disease and maintain a high degree of clinical suspicion when assessing patients.
Following the substantial increase in scarlet fever during the 2013/14 season, the number of notifications has remained elevated across most parts of England. Weekly increases in numbers are currently being seen in line with the usual seasonal pattern, but substantially higher than those reported last season (figure 1). A total of 6,225 notifications of scarlet fever between weeks 37 to 04 of 2017/18 were made to PHE compared to 3,764 for this period last season, with 719 notifications received for the most recent week (week 4, 22-28 Jan).
Rates of notified scarlet fever cases so far this season were highest in the North East at 19.0 per 100,000 population, followed by the North West (14.6), East Midlands (14.4) and Yorkshire & Humber (14.4) regions. The East of England had the lowest rate at 6.1/100,000 (Table 1). All regions have higher notifications than for the same point last season.
The age distribution of cases notified so far for this season remains similar to previous years (median 4y; range < 1y to 96y), with 89% being children under 10 years and 5% being adults ( ≥ 18y).
Antimicrobial susceptibility tests on GAS identified from throat swabs (a common GP test for confirmation of scarlet fever) in December 2017 and January 2018 indicates that 7%, 4%, 7% and 0% are non-susceptible to erythromycin, clindamycin, tetracycline and penicillin respectively. This is in line with what is expected for GAS.
Invasive Group A streptococcal infection(Continue . . .)
So far this season (week 37 to 03 2017/18), laboratory notifications of iGAS disease reported through routine laboratory surveillance in England total 744 cases, higher than the average for the previous five years (483 notifications) and above the range seen since 2012 (381 to 586; figure 2). All of the nine English regions have higher rates of iGAS infection compared with the same point last season. The highest rates being reported in the Yorkshire & Humber and North East regions (both 1.7 per 100,000 population), followed by the North West (1.6/100,000) and South West (1.6) regions (Table 1).
Due to this early spike in Scarlet Fever cases the UK's PHE has issued a statement urging vigilance among parents in looking for signs of the illness in their children.
For some earlier blogs on this nearly-decade-long rise in Scarlet Fever, you may wish to revisit:Public Health England (PHE) is advising parents to be aware of the signs and symptoms of scarlet fever following a substantial increase in reported cases...
CDC’s Scarlet Fever: A Group A Streptococcal Infection information page.