Scarlet fever primarily affects children under the age of 10, as adults generally develop immunity as they grow older. Untreated, infection can occasionally lead to serious illness, and even death.
Far less common, albeit considerably more serious, is a related illness called iGAS (invasive Group A Strep), which indicates infection of the bloodstream, drisk for the general populationeep tissues, or lungs, and may result in severe (and frequently fatal) cases of necrotizing fasciitis and streptococcal toxic shock syndrome.
Scarlet fever began to rise - first in Asia (see Hong Kong: Scarlet Fever In 2012) - and then about 8 years ago in the UK, reaching its peak in 2018 (see UK: `Exceptional' Scarlet Fever Season Continues) which was followed by a deadly outbreak of iGAS in Essex in 2019.Bacteria can evolve over time creating more infectious, antibiotic resistant, or more pathogenic strains. Strep A strains are identified by changes in their M-protein gene sequence (emm types) – and within these types new variants can emerge.
Due to social distancing and other pandemic mitigation measures, the incidence of Scarlet Fever, iGAS, and other non-COVID respiratory diseases dropped markedly during the pandemic, but as they have been relaxed, these old scourges have been returning.
Last week, in UK: Unseasonable & Robust Increase In Scarlet Fever/iGAS Cases, we looked at the unusually strong, and out-of-season increase in Strep A infections in England. Since then other countries have reported similar increases, leading to the release of a Risk Assessment overnight by the WHO (excerpts below).
Increased incidence of scarlet fever and invasive Group A Streptococcus infection - multi-country
15 December 2022Situation at a glance
As of 8 December 2022, at least five Member States in the European Region, reported to WHO an increase in cases of invasive group A streptococcus (iGAS) disease and in some cases also scarlet fever. An increase in iGAS-related deaths has also been reported in some of these countries. Children under 10 years of age represent the most affected age group.
Group A Streptococcal (GAS) infection commonly causes mild illnesses such as tonsillitis, pharyngitis, impetigo, cellulitis and scarlet fever. However, in rare instances, GAS infection can lead to invasive iGAS, which can cause life-threatening conditions.
The observed increase may reflect an early start to the GAS infection season coinciding with an increase in the circulation of respiratory viruses and possible viral coinfection which may increase the risk of invasive GAS disease. This is in the context of increased population mixing following a period of reduced circulation of GAS during the COVID-19 pandemic.
In light of the moderate increase in cases of iGAS, GAS endemicity, no new emm gene sequence type identified and no reports of increased antibiotic resistance, WHO assesses that the risk for the general population posed by iGAS infections is low at present.
Description of the situation
During 2022, France, Ireland, the Netherlands, Sweden, and the United Kingdom of Great Britain and Northern Ireland, have been observing an increase in cases of invasive group A streptococcus disease and scarlet fever, mostly affecting children under 10 years of age. The increase has been particularly marked during the second half of the year.
In France, since mid-November 2022, clinicians have reported to Santé Publique France (SpF) and the Regional Health Agencies (ARS), an unusual increase in the number of iGAS cases and the detection of iGAS clusters. Some pediatric cases have been fatal. On 8 December, SpF published a status update reporting an increase in the number of iGAS infections in France since the beginning of 2022 in different regions (Occitanie, Auvergne-Rhône-Alpes, Nouvelle-Aquitaine), mainly in children under 10 years of age. SpF also detected an increase in cases of scarlet fever reported in outpatient clinics in the country since September 2022.
On 6 December, the Irish Health Protection Surveillance Centre (HPSC) reported an increase in iGAS cases in Ireland since the beginning of October. In 2022, as of 8 December, 57 iGAS cases have been notified to HPSC, of which 15 were in children less than 10 years of age. Twenty-three of the 57 iGAS cases have been reported since October 2022, compared to the 11 cases reported for the same period of 2019 (pre-COVID-19 pandemic).
The Public Health Agency of the Netherlands (RIVM) observed an increase in iGAS infections among children from March 2022 onward. Data between March and July 2022 indicates increased numbers of iGAS cases caused by different known emm gene sequence types (the gene encoding the M virulence protein responsible for many Streptococcus pyogenes serotypes). This increase has thus far not subsided. Coinfections with varicella zoster and respiratory viruses were noted.
In Sweden, since October 2022, an increase in iGAS in children under 10 years of age has been noted as compared to COVID-19 pre-pandemic levels for the equivalent period. Out of the 93 cases reported from October to 7 December, 16 (17.2%) occurred among children under 10 years of age. Between October and December 2018, seven iGAS cases were reported in this age group and 10 cases in 2019. According to the Public Health Agency of Sweden, during the season 1 July 2021 through 30 June 2022, 220 cases of iGAS were reported, compared to 173 cases reported in the previous season 2020/21. The highest numbers of iGAS cases, since iGAS became notifiable in Sweden in 2004, were reported before the pandemic in 2018/19 with 794 cases (incidence 7.8 per 100 000) and in 2017/18 with 800 cases (incidence 7.9 per 100 000).
According to the UK Health Security Agency, following a higher-than-expected scarlet fever activity in the summer in England, with a decrease during August 2022, notifications from mid-September to early December have increased again, remaining above what is normally seen at this time of year. A total of 4622 notifications of scarlet fever were reported from weeks 37 to 46 of the current season (2022/23), with 851 notifications received in week 46. This compares with an average of 1294 (range 258 to 2008) for this same period (weeks 37 to 46) in the previous five years. As expected, several scarlet fever outbreaks in nurseries and schools are being reported, of which a number involve the co-circulation of respiratory viruses. Likewise, in the summer of 2022, the levels of iGAS notifications were higher than expected, and iGAS notifications are currently higher than have been recorded over the last five seasons in all age groups (average 248, range 142 to 357 notifications). As of 8 December, 509 notifications of iGAS disease were reported through laboratory surveillance in England, with a weekly high of 73 notifications in week 46 (week commencing on 14 November). So far this season and as of 8 December 2022, the United Kingdom reported 13 deaths within seven days of an iGAS diagnosis in children under 15 years in England. This compares with four deaths in the same period in the 2017 to 2018 (pre-COVID-19 pandemic) season. Antimicrobial susceptibility results from routine laboratory surveillance in the United Kingdom indicated no increased antibiotic resistance. Additionally, laboratory surveillance has not revealed newly emerging emm gene sequence types.
Epidemiology of Group A Streptococcus
Streptococcus pyogenes, also known as Group A Streptococcus, is a group of Gram-positive bacteria which can be carried in human throats or skin; it is responsible for more than 500 000 deaths annually worldwide.
Transmission occurs by close contact with an infected person and can be passed on through coughs, sneezes, or contact with a wound.
GAS infection commonly causes mild illnesses such as tonsillitis, pharyngitis, impetigo, cellulitis and scarlet fever. GAS infections are easily treated with antibiotics, and a person with a mild illness stops being contagious after 24 hours of treatment.
GAS is considered a common cause of bacterial pharyngitis in school-aged children and may also affect younger children. The incidence of GAS pharyngitis usually peaks during winter months and early spring. Outbreaks in kindergartens and schools are common. GAS pharyngitis is diagnosed by rapid antigen tests (Rapid Strep) or bacterial culture and is treated with antibiotics and supportive care. Good hand hygiene and general personal hygiene can help control transmission.
However, in rare instances, GAS infection can lead to invasive GAS, which can cause life-threatening conditions, such as necrotizing fasciitis, streptococcal toxic shock syndrome and other severe infections, as well as post-immune mediated diseases, such as poststreptococcal glomerulonephritis, acute rheumatic fever and rheumatic heart disease.
Public health response
Enhanced surveillance activities have been implemented in the countries reporting an increase in iGAS cases, together with public health messages addressing the general population and clinicians, in order to enhance early recognition, reporting and prompt treatment initiation of GAS cases. An alert has been issued to other countries to be vigilant for a similar rise in cases and to report any unexpected increased national or regional incidence of iGAS infections to WHO.
WHO continues to support countries in assessing and responding to the epidemiological situation across the region and to provide recommendations to the public.
WHO risk assessment
WHO currently assesses the risk for the general population posed by the reported increase in iGAS infections in some European countries as low, considering the moderate rise in iGAS cases, GAS endemicity, no newly emerging emm gene sequence types identified, and no observed increases in antibiotic resistance.
The risk will be continuously assessed based on available and shared information.
The latest update from the UK HSA reads:
UKHSA update on scarlet fever and invasive group A strep
Latest data from the UK Health Security Agency (UKHSA) on scarlet fever and invasive group A strep cases.
Latest data from the UK Health Security Agency (UKHSA) continues to show an out of season increase in scarlet fever and group A streptococcus infections.
So far this season (from 12 September to 11 December) there have been 7,750 notifications of scarlet fever. This compares to a total of 2,538 at the same point in the year during the last comparably high season in 2017 to 2018 – although cases in that season started to rise at a different point. In 2017 to 2018 there were 30,768 scarlet fever notifications overall across the year.
Invasive group A streptococcus (iGAS) infections remain rare. So far this season, there have been 111 iGAS cases in children aged 1 to 4 compared to 194 cases in that age group across the whole year of the last comparably high season* in 2017 to 2018. There have been 74 cases in children aged 5 to 9 years compared to 117 across the whole year of the last comparably high season in 2017 to 2018. The majority of cases continue to be in those over 15 years.
Sadly, so far this season there have been 74 deaths across all age groups in England. This figure includes 16 children under 18 in England. In the 2017 to 2018 season, there were 355 deaths in total across the season, including 27 deaths in children under 18.
*We analyse scarlet fever seasons from week 37 to week 36 the following year. The majority of cases would typically be seen from the beginning of February to April.
Dr Colin Brown, Deputy Director, UKHSA, said:Scarlet fever and ‘strep throat’ will make children feel unwell, but can be easily treated with antibiotics. Symptoms to look out for include fever, sore throat, swollen glands, difficulty swallowing, and headache. Scarlet fever causes a sandpapery rash on the body and a swollen tongue. NHS services are under huge pressure this winter, but please visit NHS.UK, contact 111 online or your GP surgery if your child has symptoms of scarlet fever or ‘strep throat’ so they can be assessed for treatment.Good hand and respiratory hygiene are important for stopping the spread of many germs. By teaching your child how to wash their hands properly with soap for 20 seconds, using a tissue to catch coughs and sneezes, and keeping away from others when feeling unwell, they will be able to reduce the risk of picking up or spreading infections.
At this time of year, there are lots of winter illnesses circulating that can make children unwell. Most of these can be managed at home and NHS.UK has information to help parents look after children with mild illness.
It is very rare that a child will go on to become more seriously ill, but parents know better than anyone else what your child is usually like, so you’ll know when they are not responding as they would normally. Make sure you speak to a healthcare professional if your child is getting worse after a bout of scarlet fever, a sore throat or respiratory infection – look out for signs such as a fever that won’t go down, dehydration, extreme tiredness, intense muscle pains, difficulty breathing or breathing very fast.
The first symptoms of scarlet fever include flu-like symptoms, including a high temperature, a sore throat and swollen neck glands (a large lump on the side of your neck).
A rash appears 12 to 48 hours later. It looks like small, raised bumps and starts on the chest and tummy, then spreads. The rash makes your skin feel rough, like sandpaper.
On white skin the rash looks pink or red. On brown and black skin it might be harder to see a change in colour, but you can still feel the rash and see the raised bumps.
