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).  

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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).  

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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).

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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%).

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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.