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Weekly count of invasive Group A Streptococcus (iGAS) cases

Last updated on Thursday, 10 April 2025 at 03:32pm

Summary

Topic
iGAS
Category
cases
API name
iGAS_cases_countByWeek

Rationale

To highlight the most recent weekly activity in invasive Group A Streptococcus (iGAS) cases.

Definition

This metric shows the weekly count of reported iGAS cases. Invasive GAS cases are reported by specimen date. This is the date the first sample was taken from an individual which resulted in the identification of the infection.

Only isolates with an invasive specimen type are included, these are specimens taken from a normally sterile site.

Methodology

Cases of iGAS are positive microbiological diagnostic test results (culture or molecular) identifying group A streptococcus from a sample taken from a normally sterile site. As invasive GAS is a notifiable infection, all positive samples will be reported to the UKHSA Second Generation Surveillance System (SGSS). This metric displays these positive samples.

SGSS is an application that stores and manages data on laboratory isolates and notifications collected through surveillance. It is the preferred method for capturing routine laboratory surveillance data on infectious diseases and antimicrobial resistance from diagnostic laboratories across England.

Positive tests that belong to the same individual are grouped together and considered one episode, or result, if they are within 14 days of each other. Positive tests results that are 14 days apart (regardless of negative tests in between) are considered as a separate episode of infection.

Group A Streptococcus (GAS) infections exhibit seasonal trends. A GAS season begins from International Standards Organisation (ISO) week 37 in one year to ISO week 36 in the following year (mid-September to mid-September).

Caveats

Data for the most recent 2 weeks by date of specimen is considered incomplete as it takes time for testing to be undertaken and for results to be available and flow via relevant laboratory reporting systems.

Data included is for England only.

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