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)