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Health Protection Scotland

Group A streptococcal infections

Background

Group A Streptococcus (GAS)  – also known as Streptococcus pyogenes  – are bacteria which can colonise the throat, skin and anogenital tract. It causes a diverse range of skin, soft tissue and respiratory tract infections, including:

In rare cases, patients may go on to develop post-streptococcal complications, such as:

  • rheumatic fever
  • glomerulonephritis

GAS can occasionally cause infections that are extremely severe. Invasive GAS (iGAS) is an infection where the bacteria are isolated from a normally sterile body site, such as the blood. Any GAS manifestation can be associated with development of streptococcal toxic shock syndrome (STSS), although patients with necrotising fasciitis are at highest risk.

GAS is spread by close contact between individuals, through respiratory droplets and direct skin contact.

It can also be transmitted environmentally, through contact with contaminated objects, such as towels or bedding or ingestion of food inoculated by a carrier.

GAS is usually diagnosed by microbiological culture of the affected site.

Since January 2010, scarlet fever is no longer a notifiable disease in Scotland. Laboratory confirmed reports of GAS from upper respiratory samples are used as a proxy for scarlet fever.

iGAS are also reported to our organisation through an enhanced questionnaire and isolates are sent to reference laboratory for further emm typing.

Guidance

Further guidance on GAS infections can be found on the Public Health England (PHE) website.

For all infection prevention and control guidance visit the A-Z ​pathogens section of the National Infection and Prevention Control Manual.

Data and surveillance

Information on laboratory positive reports of GAS infections are routinely submitted to the Electronic Communication of Surveillance in Scotland (ECOSS). GAS infection generally have a seasonal pattern of illness with peaks seen during the winter and spring months.

Levels of GAS, scarlet fever and iGAS were lower this season (October 2018 to the end of May 2019) in comparison to the 2017 to 2018 season where the levels were the highest seen since 2014 to 2015.

Figures 1, 2 and 3 are graphs showing the trends in GAS, scarlet fever and iGAS illness from season 2012 to 2013 to season 2018 to 2019.

Figure 1 is a line graph showing the weekly number of detections of Group A strep from the 2012 to 2013 season to the 2018 to 2019 season, week 20. The graph shows a seasonal trend where the number of detections usually increases in the spring each year. There was a step up in detections in season 2014 to 2015 and activity was high in season 2017 to 2018. Data for season 2018 to 2019 will change retrospectively in later weeks as more data is received.

 

Figure 2 is a line graph showing the weekly number of detections of Group A strep from respiratory samples as a proxy for Scarlet fever from the 2012 to 2013 season to the 2018 to 2019 season, week 20. The graph shows a seasonal trend where the number of detections usually increases in the spring each year. There was a step up in detections in season 2014 to 2015 and activity was high in season 2017 to 2018. Data for season 2018 to 2019 will change retrospectively in later weeks as more data is received.

 

Figure 3 is a bar chart showing the quarterly number of detections of invasive group A strep from the 2012 to 2013 season to the 2018 to 2019 season, week 20. Activity is usually higher in quarter one of each year and activity was highest in seasons 2014 to 2015 and 2017 to 2018.

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Streptococcal infections