Friday, April 08, 2016

UK PHE: Scarlet Fever Still Rising

UK PHE Infection report  11 March 2016

# 11,244

After more than a decade of decline and flat numbers (see chart above) the incidence of Scarlet Fever began rising dramatically in 2014 in the UK, and for the third year running PHE is reporting the highest number of cases in decades (see 2015's UK: Scarlet Fever On The Ascendant (Again)). 

The chart above only goes through week 9, but hints at things to come, and today the UK's PHE has confirmed that the number of cases reported in the past week exceed anything seen for decades.

Scarlet Fever primarily affects children under the age of 12. It is highly contagious, and while there is no vaccine, antibiotics are generally effective when treated early.

First the report, then I'll be back with a bit more. 

Public Health England (PHE) has reported a continued increase in cases of scarlet fever across England with 1319 new cases between 21 to 27 March, the highest weekly total recorded in recent decades (data available from 1982 onwards). 

A total of 10,570 cases of scarlet fever have now been reported since the season began in September 2015. 

Scarlet fever is a seasonal illness which should be treated with antibiotics and cases of the illness usually peak at this time of year.

An increase in invasive disease caused by the same bacterium group A streptococcus (GAS) which causes scarlet fever has also been seen in England. A total of 593 cases of invasive GAS infection, such and bloodstream infection or pneumonia, have been notified so far for 2016 compared to 440 cases for the same period last year (January to March). This year GAS seasonal activity coincides with the seasonal influenza activity owing to the late flu season. Influenza and invasive GAS co-infection is a rare but well-recognised occurrence. 

Whilst the elderly remain most at risk of invasive GAS infection, increased levels of disease compared to last year have been seen in young adults and children less than 5 years old, the age groups most affected by influenza in recent weeks. There’s no suggestion of an increase in invasive GAS infection in patients diagnosed with scarlet fever.

This is the third season in a row in which elevated scarlet fever activity has been  noted. A total of 15,637 notifications were made in England and Wales in 2014, rising to 17,590 in 2015. Weekly activity so far this season has been similar or slightly above for that last year.

GAS bacteria are spread by direct person-to-person contact with an individual carrying the bacteria or indirectly through contact with bacteria in the environment. Keeping wounds clean and practising hand hygiene can decrease chances of catching a GAS infection.
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.

And according to a report released last month by the PHE, iGAS cases are up this year as well.


Invasive group A Streptococcus
Laboratory reports of iGAS disease notified through routine laboratory surveillance in England total 811 cases so far this season (week 37 to 08 2015/16), higher than the average for the previous five years (618 reports; figure 3). Notifications of iGAS infection spiked in week 7 with 67 notifications made for this week. Twelve of 15 English regions have reported higher than average iGAS cases so far this season (table 1), with the highest population rates in Yorkshire & Humber at 2.2 per 100,000 population, closely followed by the East Midlands (2.2), Devon, Cornwall & Somerset (2.1) and the North East (2.0).
 (Continue . . .)

We've seen other unusual outbreaks of Scarlet Fever around the world, including in Mainland China, and in Hong Kong in 2011-2012 (see Hong Kong: Scarlet Fever In 2012).

Exactly why this old scourge is on the comeback trail isn't known, although in late 2014 a 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).

The UK Scarlet Fever epidemic is expected to peak in the next few weeks.

Meanwhile, the PHE strongly urges parents to consult their GPs immediately if their children develop symptoms of scarlet fever (sore throat, headache and fever accompanied by a characteristic rash) so they can be treated with antibiotics.

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