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| Dramatic Increase In Scarlet Fever In UK |
#14,299
For the past 5 years we've been following a dramatic increase in Scarlet Fever and invasive Group A Streptococcus (iGas) in the UK (see 2018's UK: `Exceptional' Scarlet Fever Season Continue).
As the chart above indicates, rates of scarlet fever prior to 2014 (blue line) were dramatically lower than after 2014 (orange line).
The causative bacterium for both of these infections is 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.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.
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 children may be affected, iGAS most commonly occurs in older adults. Over the summer we followed an unusual outbreak in Essex, which as of the latest update has totaled 37 cases, 33 which are confirmed as part of this outbreak and four which are probable cases. Fourteen have died.
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 the past 5 years in the UK.We've a new study, published yesterday in The Lancet, which finds not only a steady rise in the emm1 type in NW London (5% in 2014 to 33% in 2016), but identifies it as a new variant that has an increased capacity to produce scarlet fever toxin.
First a link to the study, and a few excerpts from the Abstract, followed by a link and excerpts from the Lancet's press release. Follow the link to read the full study.
Emergence of dominant toxigenic M1T1 Streptococcus pyogenes clone during increased scarlet fever activity in England: a population-based molecular epidemiological study
Nicola N Lynskey, PhD †Elita Jauneikaite, PhD † Ho Kwong Li, MBBS Xiangyun Zhi, PhD Claire E Turner, PhD Mia Mosavie, MSc et al.
Open Access Published:September 10, 2019 DOI: https://doi.org/10.1016/S1473-3099(19)30446-3
Summary
Background
Since 2014, England has seen increased scarlet fever activity unprecedented in modern times. In 2016, England's scarlet fever seasonal rise coincided with an unexpected elevation in invasive Streptococcus pyogenes infections. We describe the molecular epidemiological investigation of these events.
Methods
We analysed changes in S pyogenes emm genotypes, and notifications of scarlet fever and invasive disease in 2014–16 using regional (northwest London) and national (England and Wales) data. Genomes of 135 non-invasive and 552 invasive emm1 isolates from 2009–16 were analysed and compared with 2800 global emm1 sequences.
(SNIP)Transcript and protein expression of streptococcal pyrogenic exotoxin A (SpeA; also known as scarlet fever or erythrogenic toxin A) in sequenced, non-invasive emm1 isolates was quantified by real-time PCR and western blot analyses.
Interpretation
(Continue . . . )A dominant new emm1 S pyogenes lineage characterised by increased SpeA production has emerged during increased S pyogenes activity in England. The expanded reservoir of M1UK and recognised invasive potential of emm1 S pyogenes provide plausible explanation for the increased incidence of invasive disease, and rationale for global surveillance.
News Release 10-Sep-2019
The Lancet Infectious Diseases: New strain of strep a is causing scarlet fever and invasive infections in England and Wales
Scientists warn vigilance is needed to monitor impact of new bacterial strain on public health
The Lancet
Scientists studying scarlet fever have identified a new strain of disease-causing bacteria, which may explain a rise in more serious Strep A infections in England and Wales, according to results from cases in London and across England and Wales from 2014-16 published in The Lancet Infectious Diseases journal.
In 2014, England experienced the biggest surge in scarlet fever cases since the 1960s. Numbers continued to increase, with 15,000 cases in 2014, 17,000 in 2015 and over 19,000 in 2016. Symptoms, which affect young children, include a high temperature, sore throat, and a pink-red rash that feels like sandpaper [1].
Scarlet fever is caused by toxins released by the bacterium Streptococcus pyogenes, also known as Strep A, and cases follow a seasonal pattern peaking between March and May. Scarlet fever is easily treated with antibiotics. Cases of invasive infections caused by the same bacterium also increased in 2016 compared to the previous five years.
In this new study, the authors provide an explanation for the association between increased incidence of scarlet fever and increased incidence of more serious invasive infections such as bloodstream infections. They uncovered a new strain of Streptococcus pyogenes with increased capacity to produce scarlet fever toxin.
"Given that this strain has an apparently enhanced ability to cause all types of Strep A infection, it is important to monitor the bacterium both here and globally," says joint first author, Dr Nicola Lynskey from Imperial College London, UK. [2]
(SNIP)
"The distinct bacterial clone we have discovered appears so far to be largely limited to the UK, but the fact that we have identified two examples of it elsewhere suggests it has the potential to spread internationally and may already be present in other countries.
However, it's also possible that the lineage will not last. In the past, some lineages have appeared and then disappeared quickly. Only further research on recent strains will provide more insights." says senior author Professor Shiranee Sriskandan from Imperial College London, UK. [2]
Writing in a linked Comment, Professor Mark Walker from the University of Queensland, Australia, says: "The continuing increase in scarlet fever and invasive disease notifications in the UK exemplifies the essential need to install global surveillance systems and address the increased GAS disease activity as a public-health priority. We believe that the report by Lynskey and colleagues sends out an important warning for the global public health community - recently emerging scarlet fever GAS strains have enhanced invasive potential which may have profound implications for the future global health burden."
(Continue . . .)
This isn't the first virulent Scarlet Fever variant to appear in recent years. In 2011 and 2012 we followed an unusual erythromycin resistant (but still sensitive to Penicillin & other 1st generation cephalosporins) scarlet fever outbreak in Hong Kong (see Hong Kong: Scarlet Fever In 2012), which resulted in a small number of pediatric fatalities.
A 2014 Nature Genetics journal article attributed Hong Kong’s severe outbreak to the emergence of a new emm12 variant (see Emergence of scarlet fever Streptococcus pyogenes emm12 clones in Hong Kong is associated with toxin acquisition and multidrug resistance).Reminders that nature's laboratory is open 24/7, and even old foes can learn new tricks.
