Group A Streptococcus (GAS) quarterly surveillance report
September to December 2023

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.

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.

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 27 August 2024.

Main points

Activity

All iGAS activity has decreased by 63.1% between Quarter 1 (Jan to Mar 2023) with 195 cases and Quarter 3 (Jul to Sep 2023) with 72 cases, but was stable in Quarter 4 (Sep to Dec 2023) with 74 cases.

Age

Most iGAS cases – 52.7% – have occurred in older age groups, particularly those aged 45 years and over between October and December 2023.

Mortality

55 deaths amongst iGAS cases have been reported to PHS between in 2023, with a case fatality rate (CFR) of 11.8% (Table 1).

Typing

Emm type 1.0 was the most common emm type reported to ECOSS with 55.6% of all typed iGAS cases in 2023 (Table 2).

Results and commentary

General trend

In Quarter 4 (October to December 2023, weeks 40 to 52), there were 74 reports of GAS isolated from a normally sterile site (iGAS), compared to 72 in Quarter 3 (July to September 2023, weeks 27 to 39).

The quarterly iGAS case numbers were highest in Quarter 1 (January to March 2023) at 195.

Overall, the quarterly case numbers between 2017 and 2023 ranged between 11 and 195 (Figure 1).  

[insert figure 1]

Age

Most iGAS cases – 277 out of 465 (59.6%) – in 2023 have been in individuals aged 45 years or older followed by those aged 15 to 44 years (19.4%).

Cases aged 14 years and below accounted for 18.7% of all reports (Figure 2).  

[insert figure 2]

NHS board

NHS board-level data showed that all 14 NHS boards in Scotland have reported iGAS cases between January and December 2023.

In 2023, three of these NHS boards reported less than five cases each – Western Isles (one case) and Orkney and Shetland (three cases each).

Most of these cases were in the Greater Glasgow and Clyde – 106 out of 465 (22.8%) – and Lothian – 80 out of 465 (17.2%) – health boards (Figure 3).

[insert figure 3]

Clinical presentation

Not all cases have a surveillance form returned.

Many have more than one clinical presentation.

In addition, technical challenges arise when matching clinical presentations with case records where the specimen date and case report dates differ.

Therefore, the clinical presentation data is less than the case report data, but the pattern mirrors that of the case report data.

In 2023, clinical presentation data was captured for 61.3% (285 out of 465) of the case reports.

The most common clinical presentation was bacteraemia (63.9%) followed by necrotising fasciitis and streptococcal toxic shock syndrome (STSS) with 7.7% each and surgical wound infection (7.4%).

[insert figure 4]

iGAS mortality

In 2023, to a total of 55 iGAS deaths were reported to PHS. This is a case fatality rate (CFR) of 11.8%.

This compares with 19 (6.8% CFR) in the previous year.

Of these deaths, four (7.3% CFR) were in children under 16 years of age compared to three (15.8%) in 2022 (Table 1).

iGAS emm types

Results from iGAS typing data for the year 2023 shows that 71.6% (333 out of 465) of iGAS cases had an emm type reported.

Emm 1.0 accounts for the majority – 185 cases (55.6%) – followed by emm type:

• 12.0 – 22 cases (6.6%)
• 89 – 15 cases (4.5%)
• 76.0 – 12 cases (3.6%)
• 4 –  9 cases (2.7%)
• 1.25 – 7 cases (2.1%)
• 28.0 – 7 cases (2.1%)

This is similar to the distribution observed in previous years. 

Discussion

Overall activity

When compared to Quarter 1 (January to March 2023, weeks 1 to 13), iGAS activity in Quarters 2 to 4 has decreased.

This would be expected according to the pattern of iGAS observed in previous seasons.

Apart from years 2017 and 2022, iGAS activity was highest in the first quarter of each year. In 2017, iGAS activity was highest in the second quarter but was highest in Quarter 4 of 2022, coinciding with high number of cases seen during the 2022/2023 season.

Age

For years 2018, 2019, 2020, 2021 and 2023, iGAS activity was highest in the first quarter (January to March).

During years 2018, 2019, 2021 and 2023, activity was lowest in the third quarter (July to September).

In relation to age, most iGAS cases were in the older age groups with those aged 45 years and over accounting for 52.7% of the cases in the fourth quarter of 2023 and 70.8% of all the cases in quarter 3 2023.

The 15 to 44 years age groups accounted for 13.9% and 28.4% of all iGAS cases in the third and fourth quarters of 2023, respectively.

NHS board activity

In 2023, all health boards reported at least one case of iGAS.

Activity was highest in Greater Glasgow and Clyde (GGC) with 22.8% (106 out of 465) of the cases and Lothian with 17.2% (80 out of 465) of the cases.

In Quarter 4 2023, GGC and Lothian accounted for 23% of the cases each (17 out of 74).

In 2023, Orkney (three cases), Shetland (three cases) and Western Isles (one case) reported less than five cases each.

It is important to note that these boards have lower populations compared to the other health boards.

iGAS mortality

Meanwhile, the number of iGAS cases and proportion of death were highest in 2023 (465 cases with 55 deaths – a CFR of 11.8%).

The second highest number of cases (381) and CFR (8.9%) was observed in 2019.

During the period 2017 to 2023, the CFR ranged from 2.8 to 11.8%, although historical recording of iGAS cases and related deaths may be incomplete.

iGAS emm type

There were 44 different emm types reported in 2023 among the 71.6% of the cases that were typed.

As observed in previous years, emm type 1.0 with 55.6% of the typed cases was the most common.

The second most common emm type, 12.0, only had 22 cases (6.6%), while 17 emm types had one case reported each.

Conclusion

In summary, iGAS case reports decreased by 63.1% between Quarter 1 2023 and Quarter 3 2023.

This pattern, with activity at a peak in Quarter 1 and lowest in Quarter 3, was observed in five out of the seven-year study period between 2017 and 2023.

In 2023, most of the iGAS (52.7%) cases were in those aged 45 years and above.

There were 55 iGAS deaths reported among the cases in 2023 with a CFR of 11.8%.

Most of the iGAS samples in 2023 were typed (71.6%, 333/465) and emm type 1.0 was the most common type accounting for 55.6% (185/333) of those that were typed.

Contact

General enquiries

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

Further information

Statistical designation

Experimental statistics are official statistics which 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 Experimental label will be removed.

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

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 Health Department
• 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.​

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