Saturday, December 9, 2023
| Term | Definition |
|---|---|
| Invasive group A Streptococcus (iGAS) infection | Isolation of GAS from a normally sterile site, either by PCR or culture. For this study, iGAS also includes GAS infections in which GAS was isolated from a normally nonsterile site in combination with a severe clinical presentation, such as streptococcal toxic shock syndrome or necrotizing fasciitis |
| Group A Streptococcus (GAS) infection | Isolation of GAS from a non-sterile site in combination with clinical symptoms attributable to bacterial infection including fever (temperature ≥38°C), sore throat, wound infection, or cellulitis |
| Group A Streptococcus carriage | Isolation of GAS from a nonsterile site but no symptoms attributable to infection with this microorganism |
| Home healthcare (HHC) | Community health services, including district nursing teams, general practitioners, podiatry (chiropody), community midwifery, hospital outreach, and palliative care, which provide medical or nursing care within a patient’s home |
| Residential care | Live-in accommodation that provides 24-hour care and support to its residents |
Table 1. Definitions used in a study of invasive group A Streptococcus infection associated with home healthcare, England, 2018–2019
| Outbreak no. | No. iGAS cases | No. GAS cases† | No. deaths | No. days from first to last case | No. cases without identified HHC input | emm type | WGS |
|---|---|---|---|---|---|---|---|
| 1 | 14 | 2 | 2 | 136 | 1 | 87 | N |
| 2 | 7 | 1 | 2 | 148 | 0 | 94 | N |
| 3 | 6 | 0 | 3 | 222 | 0 | 94 | Y |
| 4 | 7 | 0 | 2 | 388 | 0 | 89 | Y |
| 5 | 5 | 5 | 2 | 179 | 2 | 89 | N |
| 6 | 3 | 0 | 0 | 75 | 0 | 1 | Y |
| 7 | 4 | 0 | 0 | 219 | 0 | 1 | Y |
| 8 | 2 | 0 | 1 | 3 | 0 | 89 | Y |
| 9 | 9 | 1 | 1 | 507 | 0 | 89 | Y |
| 10 | 39 | 95 | 15 | 487 | 1 | 44 | Y |
| Total | 96 | 104 | 28 | NA | 4 | NA | NA |
Table 2. Summary of home healthcare–associated invasive group A Streptococcus infection outbreaks, England, 2018–2019*
*GAS, group A Streptococcus; HHC, home healthcare; iGAS, invasive group A Streptococcus; NA, not applicable; WGS, whole-genome sequencing. †Noninvasive GAS was not systematically investigated or recorded in all outbreaks. Available data did not enable distinction between carriage and noninvasive infection.
| Characteristics | No. (%) | IQR (range) |
|---|---|---|
| All outbreaks, n = 10 | ||
| Total cases | 96 (100) | NA |
| Total deaths | 28 (29) | NA |
| Median cases | 7 | 4–9 (2–39) |
| Median outbreak duration, d | 199 | 139–347 (3–507) |
| Outbreaks with case data, n = 9 | ||
| Case-patient characteristics, n = 57 | ||
| Median age, y | 83 | 77–90 (42–100) |
| Sex | ||
| F | 39 (68) | NA |
| M | 18 (32) | NA |
| Median days between cases | 21 | 6–46 (1–225) |
| Type of residence, n = 48 | ||
| Residential care | 17 (35) | NA |
| Own home | 31 (65) | NA |
| HHCW exposure, n = 96 | ||
| Patient receiving care | 92 (96) | NA |
| Household contact of recipient | 2 (4) | NA |
| None identified† | 2 (4) | NA |
Table 3. Characteristics of home healthcare–associated invasive group A Streptococcus infection outbreaks, England, 2018–2019*
*HHCW, home healthcare worker; NA, not applicable.
†Cases linked to outbreaks through whole-genome sequencing but without any identified connection to home healthcare services.
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In this study, we included HHC-associated iGAS outbreaks identified in England during January 1, 2018–August 31, 2019. We identified outbreaks cross-referenced from PHE’s case and outbreak logging software, HPZone, and the RVPBRU streptococcal outbreak dataset. In addition, we contacted the healthcare-associated infection leads of each PHE center to identify any outbreaks not reported in the 2 datasets. We chose this short timeframe to ensure we could examine each outbreak in detail and maximize accurate data collection.
We included outbreaks with ≥2 cases of iGAS infection of the same emm type and linked to the same defined HHC service. We excluded outbreaks in which other exposures offered a more plausible transmission route, such as within residential care or another healthcare setting.
The inclusion criteria for individual cases within an outbreak varied between outbreaks and were set by the investigating outbreak control team (OCT). The broadest inclusion criterion for cases was defined as iGAS of the same emm type linked to the same defined HHC service. In outbreaks for which WGS was deployed, the inclusion criteria were honed to include only cases linked by sequencing, defined as ≤5 SNPs between strains. Noninvasive GAS infections and colonization were not systematically investigated or recorded in all outbreaks.
To investigate temporal trends in outbreaks, we also searched HPZone for outbreaks during January 1, 2013–December 31, 2017. We did not search other sources for outbreaks during this period and did not collect further data because the outbreaks were too distant in time for data to be accurate. We provide operational definitions used in this study (Table 1).
We conducted a 1-hour qualitative semistructured telephone interview with the chair of each OCT or other nominated staff member. We asked participants standardized open-ended questions grouped into themes surrounding outbreak identification, microbiology, investigation, and infection control. We encouraged participants to elaborate on answers by asking probing follow-up questions and incorporated themes that emerged in early interviews into subsequent interviews. We explored barriers to investigation and management in a similar way and encouraged participants to identify learning points and recommendations for future outbreaks. We collected data by using a standardized interview protocol and captured audio recordings of interviews to enable further review by the interviewer. We used thematic analysis to analyze qualitative data.
When available, we collected quantitative data regarding the number of HHCWs and patients screened and treated. We collected standardized pseudonymized data on case-patients, including age, iGAS onset date, hospitalization, and outcome. When sequencing was performed, we identified cases linked by sequence data (these data are not reported here). We recorded and analyzed data in Excel (Microsoft, https://www.microsoft.com) and Stata version 15 (StataCorp LLC, https://www.stata.com) and managed data in line with PHE’s information governance policy.
This study was performed by PHE as part of its legal obligation to collect and process information about communicable disease surveillance and control under section 251 of the National Health Service Act 2006 (https://www.legislation.gov.uk/ukpga/2006/41/contents). No further ethics approval was required.
