Friday, March 09, 2018

UK PHE: Scarlet Fever Cases Continue To Rise
UK PHE Scarlet Fever Report


Just over a month ago, in UK Reporting Heavy Scarlet Fever Activity For 5th Year Running, we looked at what looked to be an unusually early start to the UK's Scarlet Fever season, which normally peaks in April or May.
After a decade of decline in the UK, Scarlet Fever cases began to climb in 2013, and have remained elevated for five years running.
While the reasons remain unclear (see The Lancet's Nov 2017 report  Resurgence of scarlet fever in England, 2014–16: a population-based surveillance study), Scarlet Fever has been on the ascendant since 2009 across much of Asia, and more recently in the UK.

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. 
Far less common, albeit considerably more serious, is a related illness 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.

UK PHE Scarlet Fever Report
This year, PHE reports iGAS cases are also rising sharply (see chart below), running nearly 75% higher for this time of the year than the average over the past 5 years. 

UK PHE Scarlet Fever Report

Once again Public Health England urges vigilance about spotting signs of scarlet fever, as they release a new monthly report (see excerpts below).

Group A streptococcal infections: second report on seasonal activity in England, 2017/18

On-going surveillance of scarlet fever in England indicates weekly notifications are higher than those reported at this point in the last four seasons (weeks 37 to 9, 2013/14 to 2016/17) with the current trajectory indicating the potential for further increases over the coming weeks [1].
Alerts have been sent to GPs, microbiologists and local authorities raising awareness of the national increase in scarlet fever, highlighting actions to be taken for every case, including: prompt notification to local Public Health England (PHE) Health Protection Teams (HPTs); obtaining throat swabs (prior to commencing antibiotics) when there is uncertainty about a diagnosis or when a case is part of an outbreak; and reinforcing the need for excluding cases or possible cases from school/work until 24 hours of antibiotic treatment has been received [2].
The number 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.

There has been a steep increase in scarlet fever notification in the first part of the 2017/18 season. Since the peak reported in the 2013/14 season, levels of scarlet fever have remained elevated. Whilst the rate of increase in both notifications and GP consultation rates for scarlet fever reduced during February [3], both are showing slight increases as we move into March suggesting a temporary suppression of transmission over the school half-term, as seen in previous years. Continued increases over the coming weeks are likely with peak activity typically occurring between weeks 11 and 13.
Close monitoring, rapid and decisive response to potential outbreaks and early treatment of scarlet fever is vital, especially given the potential complications associated with GAS infections.

The number of cases of iGAS disease notified through routine laboratory surveillance in England at the start of 2018 is of concern, with more than 40 per cent more iGAS cases being notified at this point in the season compared with levels seen in recent seasons.
Whether this increase is related to the heightened scarlet fever activity, or influenza activity, a known predisposing factor, is unknown. Clinicians, microbiologists and HPTs should continue to be mindful of potential increases in invasive disease and maintain a high index of suspicion in relevant patients as early recognition and prompt initiation of specific and supportive therapy for patients with iGAS infection can be life-saving.
        (Continue . . . )

For some earlier blogs on this nearly-decade-long rise in Scarlet Fever, you may wish to revisit:

Hong Kong: Scarlet Fever Cases Rise Sharply
UK PHE: Scarlet Fever Still Rising
UK: Scarlet Fever On The Ascendant (Again)
UK : Sharp Rise In Scarlet Fever Cases In 2014
For more on the disease, here is the CDC’s Scarlet Fever: A Group A Streptococcal Infection information page.

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