Group A Streptococcus (GAS) quarterly surveillance report
April to June 2024

About this release

Our quarterly update

This release by Public Health Scotland (PHS) provides quarterly information on Group A Streptococcal (GAS) infections.

In Scotland, GAS infections are monitored using routine laboratory data.

Under the Public Health (Scotland) Act 2008, cases of invasive GAS (iGAS) are notifiable but scarlet fever is not notifiable in Scotland.

Culture and PCR-positive GAS and iGAS specimens from all laboratories in Scotland are submitted to PHS using the Electronic Communication of Surveillance in Scotland (ECOSS) system.  

GAS infections are classified as invasive if they have been isolated by culture or accredited molecular methods (such as PCR) from a normally sterile body site, such as:

• blood
• cerebrospinal fluid
• joint aspirate
• pericardial peritoneal-pleural fluids
• bone
• endometrium
• deep tissue or deep abscess at operation or post-mortem

An iGAS-related death is defined as death (from all causes) within seven days of a positive iGAS specimen. PHS actively follows up outcomes for all reported cases after 30 days to make sure they are captured. 

iGAS cases are also reported to PHS using an enhanced surveillance questionnaire, which provides further information on risk factors and outcomes.

Invasive GAS samples are also sent to the Scottish Microbiology Reference Laboratory (SMiRL) for further analysis and typing.

Next release

The next release of this publication will be 26 November 2024.

Main points

Activity

In Quarter 2 (Apr to Jun) 2024 there was:

• a reduction in iGAS cases of 15.3% (105 cases) when compared with Quarter 2 2023 (124 cases)
• an increase of 1.0% when compared with Quarter 1 (Jan to Mar) 2024 (104 cases)

Age

In Quarter 2 2024 the largest proportion of iGAS cases were in adults:

• aged 45 to 64 years (32.4% or 34 out of 105 cases)
• aged 65 years and older (31.4% or 33 out of 105 cases)

This compares with Quarter 2 of 2023 where the largest proportions were in adults aged 65 years and older (33.1% or 41 out of 124 cases) followed by 45 to 64 years (23.4% or 29 out of 124 cases) and 15 to 44 years (22.6% or 28 out of 124 cases).

Location

In Quarter 2 2024 most iGAS cases were reported from NHS Lothian (24.8% or 26 out of 105 cases) followed by:

• NHS Greater Glasgow and Clyde – 15.2% or 16 out of 105 cases
• NHS Tayside – 12.4% or 13 out of 105 cases

Mortality

The percentage of iGAS cases reported to have died was 9.5% (10 out of 105 cases).

This is within the range of 5.6% to 12.0% reported to have died annually between 2018 and 2023.

Typing

Emm typing was available for 76.2% (80 out of 105 cases) of iGAS cases.

Of these, emm type 3.93 accounted for 25.0% (20 out of 80 cases) of iGAS cases typed, followed by:

• emm type 89.0 – 12.5% or 10 out of 80 cases
• emm type 28.0 – 7.5% or 6 out of 80 cases.

Results and commentary

Overall, iGAS case numbers vary year to year with peaks usually observed during the winter and spring months.

Data in this report are published quarterly (every 13 weeks) and comprise iGAS laboratory reports submitted to ECOSS from NHS diagnostic laboratories and the Scottish Microbiology Reference Laboratory (SMiRL).

Please note that the data presented in this update are provisional and subject to change as data continue to be received.  

General trend

In Quarter 2 (Apr to Jun, weeks 14 to 26) 2024, there were 105 reports of GAS isolated from a normally sterile site (iGAS cases) (Figure 1).

This is a reduction of 15.3% when compared with Quarter 2 2023 (124 cases) but was similar to Quarter 1 2024 (Jan to Mar, weeks 1 to 13) 2024 (104 cases).

The iGAS case numbers in Quarter 2 between 2017 and 2024 have ranged from 16 cases (in 2021) to 124 cases (in 2023).

Figure 1 is a bar chart showing the number of invasive group A Streptococcus (iGAS) laboratory reports by year and quarter from 2017 to June 2024. It shows that in 2018, 2019, and 2021 iGAS activity peaked in the first quarter. However, peak iGAS activity was in quarter 2 in 2017 and quarter 4 in 2022.

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Figure 1: Number of invasive Group A streptococcus (iGAS) cases by quarter, 2017 to quarter 2 2024, Scotland

Age

In Quarter 2 2024, most iGAS cases were reported in adults aged 44 to 64 years (32.4% or 34 out of 105 cases) (Figure 2).

This is followed by those aged:

• 65 years and above – 31.4% (33 out of 105 cases)
• 15 to 44 years – 24.8% (26 out of 105 cases)
• 0 to 14 years – 11.4% (12 out of 105 cases)

In comparison, age distribution in Quarter 2 2023 showed most cases in those aged 65 years and over (33.1% or 41 out of 124 cases).

This was followed by those aged:

• 45 to 64 years – 23.4% (29 out of 124 cases)
• 15 to 44 years – 22.6% (28 out of 124 cases)
• 0 to 14 years – 21.0%  (26 out of 124 cases)

Figure 2 is a bar chart showing the number of iGAS laboratory reports by year and quarter from January 2017 to June 2024, stratified by four age groups: 0 to 14 years, 15 to 44 years, 45 to 64 years and 65 years and older. It shows that the age group with most iGAS cases per quarter fluctuated between those aged 65 years and over and those aged 45 to 64 years between 2017 and 2023. In quarter 2 2024, the largest number of cases were in those aged 45 to 64 years (32.4%, 34 out of 105).

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Figure 2: Number of invasive Group A Streptococcus (iGAS) cases by age group, year and quarter, 2017 to quarter 2 2024, Scotland

NHS board

In Quarter 2 (Apr to Jun) 2024, iGAS cases were reported from 12 NHS boards except:

• NHS Orkney
• NHS Western Isles

Most iGAS cases were reported from NHS Lothian (24.8% or 26 out of 105 cases) followed by:

• NHS Greater Glasgow and Clyde – 15.2% (16 out of 105 cases)
• NHS Tayside – 12.4% (13 out of 105 cases)

This compares to Quarter 2 2023 with:

• NHS Greater Glasgow and Clyde – 25.0% (31 out of 124 cases)
• NHS Lothian – 12.1% (15 out of 124 cases)
• NHS Grampian – 11.3% (14 out of 124 cases)

Figure 3 is a bar chart showing the number of iGAS laboratory reports by year and quarter from January 2017 to June 2024, stratified by health board. It shows from Q4 of 2022 to Q2 of 2024, most of the iGAS cases were reported by Greater Glasgow and Clyde and Lothian health boards. In 2023, all 14 NHS boards in Scotland reported at least 1 iGAS case. In the first two quarters of 2024, only NHS Orkney and NHS Western Isles have nit reported iGAS cases.

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Figure 3: Number of invasive Group A Streptococcus (iGAS) cases by NHS board, year and quarter, 2017 to quarter 2 2024, Scotland

iGAS deaths

In Quarter 2 2024, the percentage of iGAS cases that were reported to have died was 9.5% (10 out of 105 cases).

This is lower than the percentage reported to have died in 2023 (12.0% or 56 out of 465 cases) and within the range of 5.6% to 12.0% reported annually since 2018 (Table 1).

Most of the deaths in Quarter 2 2024 were in adults aged:

• 65 years and older – 60.0% (6 out of 10 cases)
• 45 to 64 years – 30.0% (3 out of 10 cases)

The highest case fatality rate (CFR) was also observed in adults aged:

• 65 years or older – 18.2% (6 out of 33 cases)
• 45 to 64 years – 8.8% (3 out of 34 cases)

iGAS emm types

Analysis of reference laboratory typing of isolates shows that in Quarter 2 2024, emm typing was available for 76.2% (80 out of 105 cases) of iGAS cases and identified 32 different types.

Emm type 3.93 accounted for 25.0% (20 out of 80 cases) of iGAS cases typed (Table 2a), followed by:

• emm type 89.0 – 12.5% (10 out of 80 cases)
• emm type 28.0 – 7.5% (6 out of 80 cases)

This reflects a change from 2023 (Table 2b) when emm type 1.0 was the most commonly identified emm type (55.6% or 204 out of 367 cases) followed by:

• emm type 12.0 - 6.3% (23 out of 367 cases)
• emm type 89.0 - 4.9% (18 out of 367 cases)

Discussion

Overall activity

The number of iGAS cases reported in quarter 2 2024 (105 cases) reduced by 15.3% when compared to quarter 2 2023 (124 cases) and is within the range reported in quarter 2 from 2017-2023 (16 to 124 cases).

With the exception of 2017, 2022 and 2024, iGAS activity was highest in the first quarter of each year.

As expected with seasonal patterns of iGAS activity, quarter 2 2024 iGAS case numbers were higher than reported in quarter 3 (72 cases) and quarter 4 2023 (74 cases) but similar to quarter 1 2024 (104 cases, see Figure 1).

Age

Historically, iGAS cases are more commonly reported in older adults with case numbers increasing with age.

In quarter 2 2024, most cases were reported in those aged 45-64 years (32.4%, 34 out of 105) and 65 years and older (31.4%, 33 out of 105).

When compared with quarter 2 2023, there were reductions in case numbers reported from all age groups except those aged 45-64 years and the largest proportions were in adults aged 65 years and older (33.1%, 41 out of 124) followed by 45-64 years (23.4%, 29 out of 124) and 15-44 years (22.6%, 28 out of 124) (Figure 2). 

NHS board activity

In Quarter 2 2024, all NHS boards – except NHS Orkney and NHS Western Isles – reported iGAS cases with larger NHS boards reporting most cases (Figure 3):

• NHS Lothian – 24.8% (26 out of 105 cases)
• NHS Greater Glasgow and Clyde – 15.2% (16 out of 105 cases)
• NHS Tayside – 12.4% (13 out of 105 cases)

iGAS mortality

The were 10 deaths among the 105 iGAS cases reported in Quarter 2 2024 with a case fatality rate (CFR) of 9.5%. This is within the range reported annually since 2018 (Table 1).

Most of the deaths (60.0% or 6 out of 10 cases) and the highest CFR (18.2% or 6 out of 33 cases) occurred in adults aged 65 years and above suggesting that older people are more susceptible to iGAS and its complications.

iGAS emm type

In Quarter 2 2024, emm typing was available for 76.2% of cases and 32 different emm types were identified.

Historically, emm type 1 has been the most commonly identified emm type in Scotland.

However, in Quarter 2 2024 the most common was emm type 3.93 (20 cases, 25.0%) followed by:

• emm type 89.0 – 10 cases (12.5%)
• emm type 28.0 – 6 cases (7.5%)

Between quarter 1 and quarter 2, the proportion of emm type 1.0 cases has reduced further to account for only 6.3% of the cases in quarter 2 compared to 12.2% in quarter 1. Similarly, the proportion of cases with emm type 76.0 has decreased from 8.1% in Q1 2024 to 2.55 in quarter 2 2024. By contrast, the proportion of emm type 89.0 cases has increased from 1.4% in quarter 1 2024 to 12.5% in quarter 2 2024.

The changing distribution of iGAS emm types and any potential impact on transmissibility and disease severity are not yet fully understood.

Contact

General enquiries

If you have an enquiry relating to this publication, please email phs.flu@phs.scot.

Further information

Statistical designation

Official Statistics in development are official statistics which are undergoing development and are published in order to involve users and stakeholders in their development and as a means to build in quality at an early stage.

It is important that users understand that limitations may apply to the interpretation of this data, further details of which are presented in this report.

All official statistics should comply with the UK Statistics Authority’s Code of Practice which promotes the production and dissemination of official statistics that inform decision making. Once the evaluation is completed and an enhanced report is developed that meets the needs of users and stakeholders, the 'Official Statistics in development' label will be removed.

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Alternatively, you can contact OSR by emailing regulation@statistics.gov.uk or through the OSR website.

Visit the UK Statistics Authority website for more information about the Code of Practice and Official Statistics.

Planned developments

The content of these reports will be reviewed and developed over time following feedback from stakeholders and user engagement. 

Pre-release access

Under terms of the 'Pre-Release Access to Official Statistics (Scotland) Order 2008', PHS is obliged to publish information on those receiving Pre-Release Access ('Pre-Release Access' refers to statistics in their final form prior to publication). The standard maximum Pre-Release Access is five working days.

Shown below are details of those receiving standard Pre-Release Access.

Standard pre-release access

• Scottish Government Department of Health and Social Care (DHSC)
• NHS board chief executives
• NHS board communication leads

About Public Health Scotland (PHS)

PHS is a knowledge-based and intelligence driven organisation with a critical reliance on data and information to enable it to be an independent voice for the public’s health, leading collaboratively and effectively across the Scottish public health system, accountable at local and national levels, and providing leadership and focus for achieving better health and wellbeing outcomes for the population.

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