Group A Streptococcus (GAS) quarterly surveillance report
January to March 2025
- Published
- 27 May 2025 (Latest release)
- Type
- Statistical report
- Author
- Public Health Scotland
- Topics
-
Conditions and diseases
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 26 August 2025.
Main points
Activity
- In quarter 1 of 2025, there were 73 iGAS cases reported. This has decreased by 29.8% when compared with 2024 when there were 104 notifications.
Age
- In quarter 1 of 2025, the largest proportion of iGAS cases were in adults aged 65 years and older (46.6%, 34/73) and 45-64 years (30.1%, 22/73). This age distribution is comparable to 2024.
Location
- The highest proportion of iGAS cases were reported from NHS Lothian (21.9%, 16/73) followed by NHS Tayside (19.2%, 14/73), NHS Greater Glasgow and Clyde (9.6%, 7/73), NHS Grampian (8.2%, 6/73), NHS Highland (8.2%, 6/73) and NHS Lanarkshire (8.2%, 6/73).
Clinical presentation
- The most common clinical presentation for iGAS cases was bacteraemia (57.8%, 37/64).
Mortality
- 12.3% of iGAS cases were reported to have died (9/73) which is slightly above the range of 5.6 -12.0% reported annually between 2017 and 2024.
Typing
- Emm typing was available for 83.6% (61/73) of iGAS cases. Emm types 77.0 and 83.13 each accounted for 13.1% (8/61) of iGAS cases typed, followed by emm types 4.0 and 89.0, each accounting for 9.8% of cases typed (8.9%, 6/61).
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).
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 quarter 1 2025 (weeks 1 to 13), there were 73 reports of GAS isolated from a normally sterile site (iGAS cases), which is a reduction of 29.8% when compared with quarter 1 of 2024 (104 cases).
The quarterly number of iGAS cases between quarter 1 2017 and quarter 1 2025 ranged from 11 cases (quarter 3 in 2021) to 195 cases (in quarter 1 in 2023) (Figure 1).
Age
In quarter 1 2025, most iGAS cases were reported in adults aged 65 years and above (46.6%, 34/73) and 45-64 years (30.1%, 22/73) followed by 15-44 years (20.5%, 15/73) and 0-14 years (2.7%, 2/73).
In comparison, age distribution in quarter 1 2024 was 33.7% in those aged 65 years and older (35/104), 27.9% in those aged 45-64 years (29/104), 24.0% in those aged 15-44 years (25/104) and 14.4% in those aged 0-14 years (15/104) cases (Figure 2).
NHS board
In quarter 1 2025, iGAS cases were reported from 11 NHS boards, with no cases reported from NHS Dumfries and Galloway, NHS Shetland and NHS Western Isles. The highest number of iGAS cases were reported from NHS Lothian (21.9%, 16/73) followed by NHS Tayside (19.2%, 14/73) and NHS Greater Glasgow and Clyde (9.6%, 7/73). NHS Grampian, NHS Highlands and NHS Lanarkshire each contributed 8.2% of the cases (6/73). By contrast, NHS Greater Glasgow and Clyde (21.2%, 22/104), NHS Lothian (17.3%, 18/104), Grampian (10.6%, 11/104) and NHS Lanarkshire (8.7%, 9/104) had the highest number of cases in quarter 1 2024.
iGAS emm types
Analysis of reference laboratory typing of isolates shows that emm typing was available for 83.6% (61/73) of iGAS cases, which identified 23 different emm types. Emm types 77.0 and 83.13 each accounted for 13.1% (8/61) of cases typed, followed by emm types 4.0 and 89.0 each with 9.8% (6/61) of cases (Table 1a). This reflects a change from 2024 when emm type 3.93 was the most commonly identified emm type (17.3%, 41/237) followed by emm type 1.0 (7.2%, 17/237) and emm type 89.0 (6.3%, 15/237) (Table 1b).
| Emm Type | Number typed 2025 | Percentage (%) |
|---|---|---|
| 77 | 8 | 13.1 |
| 83.13 | 8 | 13.1 |
| 4 | 6 | 9.8 |
| 89 | 6 | 9.8 |
| 28 | 5 | 8.2 |
| 11 | 4 | 6.6 |
| Others (< 4 per emm type) | 24 | 39.3 |
| Total | 61 | 100 |
Source: PHS ECOSS
| Emm Type | Number typed 2024 | Percentage (%) |
|---|---|---|
| 3.93 | 41 | 17.3 |
| 1 | 17 | 7.2 |
| 89 | 15 | 6.3 |
| 77 | 13 | 5.5 |
| 28 | 12 | 5.1 |
| 76 | 11 | 4.6 |
| 4 | 10 | 4.2 |
| 6.4 | 9 | 3.8 |
| 3.1 | 7 | 3 |
| 6 | 7 | 3 |
| 75 | 7 | 3 |
| 83.13 | 7 | 3 |
| 87 | 6 | 2.5 |
| 108.1 | 5 | 2.1 |
| 33 | 5 | 2.1 |
| 66 | 5 | 2.1 |
| 81 | 5 | 2.1 |
| 12 | 4 | 1.7 |
| Others (< 4 per emm type) | 51 | 21.5 |
| Total | 237 | 100 |
Source: PHS ECOSS
Clinical presentation
In quarter 1 2025, where information was collected (90.6%, 58/64), the most frequently reported clinical presentations were bacteraemia (57.8%, 37/64), surgical wound infections (7.8%, 5/64), Streptococcal toxic shock syndrome (STSS, 6.3%, 4/64), necrotising fasciitis (NF, 6.3%, 4/64) and pneumonia (6.3%, 4/64). This was similar to period 2017 to 2024 where most iGAS cases presented with bacteraemia while the proportions presenting with surgical wound infections, STSS, necrotising fasciitis and pneumonia varied from quarter to quarter (Figure 4).
iGAS deaths
In quarter 1 2025, 12.3% of iGAS cases (9/73) were reported to have died which is higher than the percentage reported to have died in 2024 (10.4%, 34/328) but comparable to that in 2023 (12.0%, 56/465). This was slightly higher than the reported range of 5.6%-12.0% reported annually since 2018 (Table 2). Most of the deaths in quarter 1 2025 were in adults aged 65 years and older (66.7%, 6/9) and 45-64 years (22.2%, 2/9) which was comparable to those of quarter 1 to quarter 4 2024 where most deaths were in those aged 65 years and older (55.9%, 19/34) and those aged 45-64 years (26.5%, 9/34). In quarter 1 2025, the case fatality ratio (CFR) for those aged 65 years and older was 17.6% (6/34) which was similar to that of quarters 1 to 4 2024 (17.6%, 19/108).
| Year | Number of cases | Number of deaths | Percentage died (%) |
|---|---|---|---|
| 2018 | 381 | 34 | 8.9 |
| 2019 | 262 | 21 | 8 |
| 2020 | 180 | 10 | 5.6 |
| 2021 | 64 | 4 | 6.3 |
| 2022 | 281 | 18 | 6.4 |
| 2023 | 465 | 56 | 12 |
| 2024 | 328 | 34 | 10.4 |
| 2025* | 73 | 9 | 12.3 |
Source: PHS ECOSS/iGAS enhanced surveillance database.
*Data from quarter 1 2025 only
Discussion
The number of iGAS cases reported in quarter 1 2025 (73 cases) reduced by 29.8% when compared to quarter 1 2024 (104 cases) and is within the range reported quarterly between 2017 and 2024 (11 - 195 cases). iGAS activity is usually highest in the first quarter of each year with the exception of 2017, 2022 and 2024 (Figure 1).
Historically, iGAS cases are more commonly reported in older adults and case numbers increase with increasing age. In quarter 1 2025, most cases were reported in those aged 65 years and older (46.6%, 34/73) and 45-64 years (30.1%, 22/73) (Figure 2). When compared with quarter 1 2024, there were reductions in case numbers reported from all age groups. Similarly, the largest proportions in quarter 1 2024 were in adults aged 65 years and older (33.7%, 35/104) followed by 45-64 years (27.9%, 29/104) and 15-44 years (24.0%, 25/104).
In quarter 1 2025, 11 NHS boards reported iGAS cases (there were no reports from NHS Dumfries and Galloway, NHS Shetland and NHS Western Isles), with larger NHS boards such as NHS Lothian (21.9%, 16/73) and NHS Greater Glasgow and Clyde (9.6%, 7/73) reporting most cases. NHS Tayside (19.2%, 14/73) reported a larger number of cases relative to its population size (Figure 3). NHS Ayrshire and Arran, NHS Grampian, NHS Highland and NHS Lanarkshire reported 6 cases each (8.2%, 6/73).
In quarter 1 2025, emm typing was available for 83.6% of cases and 23 different emm types were identified. In quarter 1 2025, the most common emm types identified were emm types 77.0 and 83.13 each contributing 8 cases (13.1%, 8/61) followed by emm types 4.0 and 89.0 each contributing 6 cases (9.8%, 6/61). Historically, emm type 1.0 has been the most commonly identified emm type in Scotland. However, in 2024 emm type 3.93 (41 cases, 17.3%) was the most commonly identified followed by emm type 1.0 (17 cases, 7.2%) and emm type 89.0 (15 cases, 6.3%) (Tables 1a and 1b).
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 63.8% (37/58) of cases in quarter 1 2025. Other common clinical presentations were surgical wound infections (8.6%, 5/58), STSS (6.9%, 4/58), necrotising fasciitis (6.9%, 4/58) and pneumonia (6.9%, 4/58) (Figure 4).
There were 9 deaths among the 73 iGAS cases reported in quarter 1 2025 with a case fatality rate (CFR) of 12.3%, which is slightly higher than the range reported annually since 2018 (Table 2). Most of the deaths (66.7%, 6/9) and the highest CFR (26.5%, 9/34) occurred in adults aged 65 years and above suggesting that older people are more susceptible to iGAS and its complications. By comparison, in quarter 1 2024, the proportion of deaths among those aged 65 years was 55.9% (19/34) with a CFR of 17.6% (19/108).
Contact
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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.
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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.
Our statistics comply with the Code of Practice for Statistics in terms of trustworthiness, high quality and public value. This also means that we keep data secure at all stages, through collection, processing, analysis and output production, and adhere to the Office for National Statistics ‘Five Safes’ of data privacy.
Metadata
- Publication title
Invasive Group A Streptococcus (iGAS) Quarterly Surveillance Report to Q1 2025
- Description
This report describes cases of invasive Group A Streptococcus in Scotland to quarter 1 of 2025 (weeks 1 to 13)
- 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
29 April 2025
- Release date
27 May 2025
- Frequency
Quarterly
- Timeframe of data and timeliness
January 2017 to March 2025, approximately two months in arrears.
- Continuity of data
Data from 2017 to March 2025 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
25 February 2025
- Next published
26 August 2025
- Date of first publication
28 May 2024
- Help email
- Date form completed
29 April 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.