Group A Streptococcus (GAS) quarterly surveillance report
October to December 2024
- Published
- 25 February 2025 (Latest release)
- Type
- Statistical report
- Author
- Public Health Scotland
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 (which is caused by GAS infection) is not notifiable in Scotland.
Culture and polymerase chain reaction (PCR) positive GAS and iGAS specimens from all laboratories in Scotland are submitted to Public Health Scotland (PHS) via 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.
For further information about GAS, see NHS inform.
Note that data in this report are provisional and may be subject to change as data continues to be received.
Next release
The next release of this publication will be 27 May 2025.
Main points
Activity
- In quarters 1 to 4 of 2024, there were 328 iGAS cases reported. This has decreased by 29.5% when compared with 2023 when there were 465 notifications.
Age
- In quarters 1 to 4 of 2024, the largest proportion of iGAS cases were in adults aged 65 years and older (32.9%, 108/328) and 45-64 years (30.2%, 99/328). This age distribution is comparable to 2023.
Location
- The highest proportion of iGAS cases in quarters 1 to 4 of 2024 iGAS cases were reported from NHS Lothian (21.6%, 71/328) followed by NHS Greater Glasgow and Clyde (18.0%, 59/328), NHS Tayside (10.7%, 35/328) and NHS Lanarkshire (9.5%, 31/328).
Clinical presentation
- In 2024, the most common clinical presentation for iGAS cases was bacteraemia (60.7%, 156/257).
Mortality
- 8.8% of iGAS cases were reported to have died (29/328) which is within the range of 5.6-12.0% reported annually between 2017 and 2023.
Typing
- Emm typing was available for 72.0% (236/328) of iGAS cases. Emm type 3.93 accounted for 17.4% (41/236) of iGAS cases typed, followed by emm type 1.0 (7.2%, 17/236) and emm type 89.0 (6.4%, 15/236).
Results and commentary
Overall, iGAS case numbers vary from 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.
Invasive Group A Streptococcal (iGAS)
In quarters 1 to 4 of 2024 (weeks 1 to 52), there were 328 reports of GAS isolated from a normally sterile site (iGAS cases), which is a reduction of 29.5% when compared with quarter 1 to 4 of 2023 (465 cases).
The annual number of iGAS cases between 2017 and 2024 have ranged from 64 cases (in 2021) to 465 cases (in 2023) (Figure 1).
The iGAS case numbers in quarter 1 to 3 between 2017 and 2024 have ranged from 48 cases (in 2021) to 391 cases (in 2023) (Figure 1).
Age
In quarter 1 to 4 of 2024, most iGAS cases were reported in adults aged 65 years and above (32.9%, 108/328) and 45-64 years (30.2%, 99/328) followed by 15-44 years (26.2%, 86/328) and 0-14 years (10.7%, 35/328). In comparison, age distribution in 2023 was 34.8% in those aged 65 years and older (162/465), 24.7% in those aged 45-64 years (115/465), 20.9% in those aged 0-14 years (97/465) and 19.6% in those aged 15-44 years (91/465) cases (Figure 2).
NHS board
In quarter 1 to 4 of 2024, iGAS cases were reported from 12 NHS boards, with no cases reported from NHS Orkney and NHS Western Isles. The highest number of iGAS cases were reported from NHS Lothian (21.6%, 71/328) followed by NHS Greater Glasgow and Clyde (18.0%, 59/328), NHS Tayside (10.7%, 35/328) and NHS Lanarkshire (9.5%, 31/328). By contrast, NHS Greater Glasgow and Clyde (22.8%, 106/465), NHS Lothian (17.2%, 80/465), NHS Lanarkshire (10.5%, 49/465) and NHS Grampian (8.2%, 38/465) had the highest number of cases in 2023.
iGAS emm types
Analysis of reference laboratory typing of isolates shows that emm typing was available for 72.0% (236/328) of iGAS cases, which identified 53 different types. Emm type 3.93 accounted for 17.4% (41/236) of iGAS cases typed, followed by emm type 1.0 with 7.2% (17/236) and emm type 89.0 which accounted for 6.4% (15/236) each (Table 1a). This reflects a change from 2023 when emm type 1.0 was the most commonly identified emm type (55.6%, 204/367) followed by emm type 12.0 (6.3%, 23/367) and emm type 89.0 (4.9%, 18/367) (Table 1b).
| emm type | Number typed 2024 | Percentage (%) |
|---|---|---|
| 3.93 | 41 | 17.4 |
| 1.0 | 17 | 7.2 |
| 89.0 | 15 | 6.4 |
| 77.0 | 13 | 5.5 |
| 28.0 | 12 | 5.1 |
| 76 | 11 | 4.7 |
| 4.0 | 10 | 4.2 |
| 6.4 | 8 | 3.4 |
| 3.1 | 7 | 3.0 |
| 6.0 | 7 | 3.0 |
| 75.0 | 7 | 3.0 |
| 83.13 | 7 | 3.0 |
| 87.0 | 6 | 2.5 |
| 108.1 | 5 | 2.1 |
| 33.0 | 5 | 2.1 |
| 66.0 | 5 | 2.1 |
| 81.0 | 5 | 2.1 |
| 12.0 | 4 | 1.7 |
| Other (<4 per emm type) | 51 | 21.6 |
| Total | 236 | * |
Source PHS ECOSS
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| emm type | Number typed 2023 | Percentage (%) |
|---|---|---|
| 1.0 | 204 | 55.6 |
| 12.0 | 23 | 6.3 |
| 89.0 | 18 | 4.9 |
| 76.0 | 14 | 3.8 |
| 4.0 | 9 | 2.5 |
| 1.25 | 8 | 2.2 |
| 28.0 | 8 | 2.2 |
| 87.0 | 7 | 1.9 |
| 12.37 | 6 | 1.6 |
| 3.93 | 5 | 1.4 |
| 75.0 | 5 | 1.4 |
| 108.1 | 4 | 1.1 |
| 11.0 | 4 | 1.1 |
| 77.0 | 4 | 1.1 |
| 82.0 | 4 | 1.1 |
| Other (<4 per emm type) | 44 | 12.0 |
| Total | 367 |
Clinical presentation
Where information was collected (78.4%, 257/328), the most frequently reported clinical presentations were bacteraemia (60.7%, 156/257), septic arthritis (8.2%, 21/257), pneumonia (6.2%, 16/257) and surgical wound infections (4.7%, 12/257). This was similar to 2017 to 2023 where most iGAS cases presented with bacteraemia (Figure 4).
iGAS deaths
In quarter 1 to 4 of 2024, 8.8% of iGAS cases (29/328) were reported to have died which is lower than the number and percentage reported to have died in 2023 (12.0%, 56/465) and within the range of 5.6%-12.0% reported annually since 2018 (Table 2). Most of the deaths in 2024 were in adults aged 65 years and older (62.1%, 18/29) and 45-64 years (27.6%, 8/29) which was comparable to those of 2023 where most deaths were in those aged 65 years and older (64.3%, 36/56) and those aged 45-64 years (23.2%, 13/56). The case fatality ratio (CFR) for those aged 65 years and older was 16.7% (18/108) which was lower than that of 2023 (22.2%, 36/162).
| Year | Number of cases | Number of deaths | Percentage died% |
|---|---|---|---|
| 2018 | 381 | 34 | 8.9 |
| 2019 | 262 | 21 | 8.0 |
| 2020 | 180 | 10 | 5.6 |
| 2021 | 64 | 4 | 6.3 |
| 2022 | 281 | 18 | 6.4 |
| 2023 | 465 | 56 | 12.0 |
| 2024 | 328 | 29 | 8.8 |
Discussion
The number of iGAS cases reported in 2024 (328 cases) reduced by 29.5% when compared to 2023 (465 cases) and is within the range reported annually between 2017 and 2023 (64 - 465 cases). As expected with seasonal patterns, iGAS activity was highest in the first quarter of each year with the exception of 2017, 2022 and 2024 (Figure 1). In 2024 iGAS case numbers (328 cases) were lower than reported in 2023 (465 cases) but higher than in the same time period of 2017, 2019, 2020, 2021 and 2022.
Historically, iGAS cases are more commonly reported in older adults and case numbers increase with age. In 2024, most cases were reported in those aged 65 years and older (32.9%, 108/328) and 45-64 years (30.2%, 99/328). When compared with 2023, there were reductions in case numbers reported from all age groups. Similarly, the largest proportions in 2023 were in adults aged 65 years and older (34.8%, 162/465) followed by 45-64 years (24.7%, 115/465) and 0-14 years (20.9%, 97/465).
In 2024, 12 NHS boards reported iGAS cases (there were no reports from NHS Orkney and NHS Western Isles), with larger NHS boards such as NHS Lothian (21.6%, 71/328), NHS Greater Glasgow and Clyde (18.0%, 59/328), NHS Tayside (10.7%, 35/328) and NHS Lanarkshire (9.5%, 31/328) reporting most cases (Figure 3).
In 2024, emm typing was available for 72.0% of cases and 53 different emm types were identified. Historically, emm type 1.0 has been the most commonly identified emm type in Scotland. However, in 2024 emm type 3.93 (41 cases, 17.4%) was the most commonly identified followed by emm type 1.0 (17 cases, 7.2%) and emm type 89.0 (15 cases, 6.4%).
The changing distribution of iGAS emm types and any potential impact on transmissibility and disease severity are not yet fully understood.
Bacteraemia was the most common clinical presentation for iGAS cases accounting for 60.7% (156/257) of all cases in 2024. Other common clinical presentations were septic arthritis (8.2%, 21/257), pneumonia (6.2%, 16/257) and surgical wound infections (4.7%, 12/257) (Figure 4).
There were 29 deaths among the 328 iGAS cases reported in 2024 with a case fatality rate (CFR) of 8.8%, which is within the range reported annually since 2018 (Table 1). Most of the deaths (62.1%, 18/29) and the highest CFR (16.7%, 18/108) occurred in adults aged 65 years and above suggesting that older people are more susceptible to iGAS and its complications. By comparison, in 2023, the proportion of deaths among those aged 65 years was 64.3% (36/56) with a CFR of 22.2% (36/162).
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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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Metadata
- Publication title
Group A Streptococcus (GAS): quarterly surveillance report to Q4 2024
- Description
This report describes cases of invasive Group A Streptococcus in Scotland to quarter 4 of 2024 (weeks 1 to 52).
- Theme
Invasive Group A Streptococcus Infections in Scotland.
- Topic
iGAS
- Format
HTML
- Data source(s)
Electronic Communication of Surveillance in Scotland (ECOSS)
- Date that data are acquired
23 January 2025
- Release date
25 February 2025
- Frequency
Quarterly
- Timeframe of data and timeliness
January 2017 to September 2024, approximately two months in arrears.
- Continuity of data
Data from 2017 to December 2024 is presented.
- Revisions statement
None
- Revisions relevant to this publication
None
- Concepts and definitions
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.
Information on laboratory culture-positive reports of all GAS and iGAS infections are routinely submitted to the Electronic Communication of Surveillance in Scotland (ECOSS).
iGAS cases in Scotland are notifiable under the Public Health (Scotland) Act 2008.
- Relevance and key uses of the statistics
Data are collected as part of mandatory public health surveillance providing data to monitor the epidemiology of GAS and iGAS, informing public health planning and response.
Statistics are used by PHS for surveillance purposes and published for transparency.
- Accuracy
The data are considered accurate.
Data are validated locally by partnerships.
PHS carries out further validation checks in consultation with NHS Boards, as required.
The Code of Practice for Statistics has been followed to ensure a high standard of data value, trustworthiness and quality.
- Completeness
All data returned from ECOSS is used for analysis.
- Comparability
Scottish data is regularly compared to UKHSA Group A Streptococcal disease data and information.
- Accessibility
It is the policy of Public Health Scotland (PHS) to make its web sites and products accessible according to published guidelines.
- Coherence and clarity
The report has been produced using the standard PHS publications template and is available as HTML web pages.
- Value type and unit of measurement
Number of invasive Group A Streptococcal cases.
- Disclosure
The PHS protocol on statistical disclosure is followed.
- Official Statistics accreditation
Official statistics in development.
- UK Statistics Authority Assessment
Not assessed.
- Last published
26 August 2024
- Next published
27 May 2025
- Date of first publication
28 May 2024
- Help email
- Date form completed
23 January 2025
Glossary
- CFR
Case fatality rate for iGAS is the proportion of cases of iGAS that die within 7 days of a positive specimen regardless of the cause of death. This enhanced case information is actively followed up 30 days after initial reporting.
- ECOSS
Electronic Communication of Surveillance in Scotland system
- GAS
Group A Streptococcus
- iGAS
Invasive group A streptococcal infections
- NHS
NHS Scotland, sometimes styled NHSScotland, is the publicly funded healthcare system in Scotland and one of the four systems that make up the National Health Service in the United Kingdom. It operates 14 territorial NHS boards across Scotland, supported by seven special non-geographic health boards, and Public Health Scotland.
Public Health Scotland is Scotland’s lead national body for improving and protecting the health and wellbeing of all of Scotland’s people. It is an NHS Board that is uniquely sponsored by the Scottish Government and the Convention of Scottish Local Authorities (COSLA).
- PCR
Polymerase chain reaction (PCR) is a technique used to make numerous copies of a specific segment of DNA quickly and accurately.