Thursday, November 30, 2023
|
Variable |
Overall, N = 483 |
2008–2013, n = 89 |
2014–2019, n = 394 |
|---|---|---|---|
| Sex | |||
| F | 228 (47.2) | 48 (53.9) | 180 (45.7) |
| M | 255 (52.8) | 41 (46.1) | 214 (54.3) |
| Age, y, median (interquartile range) | 62 (41–75) | 60 (37–75) | 64 (41–75) |
| Age group, y | |||
| <5 | 24 (5.0) | 4 (4.5) | 20 (5.1) |
| 5–17 | 43 (4.8) | 5 (5.6) | 18 (4.6) |
| 18–34 | 45 (9.3) | 12 (13.5) | 33 (8.4) |
| 35–49 | 58 (12.0) | 10 (11.2) | 48 (12.2) |
| 50–64 | 104 (21.5) | 20 (22.5) | 84 (21.3) |
| 65–79 | 147 (30.4) | 21 (23.6) | 126 (32.0) |
| ≥80 | 92 (17.0) | 17 (19.1) | 65 (16.5) |
| Race/ethnicity | n = 444† | n = 83† | n = 361† |
| Hispanic | 22 (5.0) | 2 (2.4) | 20 (5.5) |
| Non-Hispanic | |||
| White | 390 (87.8) | 74 (89.2) | 316 (87.5) |
| Black | 4 (0.9) | 1 (1.2) | 3 (0.8) |
| American Indian/Alaska Native | 18 (4.1) | 5 (6.0) | 13 (3.6) |
| Asian | 5 (1.1) | 1 (1.2) | 4 (1.1) |
| Native Hawaiian/Pacific Islander | 5 (1.1) | 0 (0.0) | 5 (1.4) |
| Residence type | n = 428* | n = 71* | n = 357* |
| Private residence | 349 (81.5) | 56 (78.9) | 293 (82.1) |
| Long-term care or nursing facility | 63 (14.7) | 13 (18.3) | 50 (14.1) |
| Homeless | 9 (2.1) | 1 (1.4) | 8 (2.2) |
| Correctional facility | 7 (1.6) | 1 (1.4) | 6 (1.7) |
Table 1. Demographics of patients with invasive group A Streptococcus disease, overall and by 6-year periods, Idaho, USA, 2008–2019*
*Values are no. (%) patients except as indicated. †Excludes cases with missing data.
|
Variable |
Unadjusted odds ratio* (95% CI) |
p value |
Adjusted odds ratio† (95% CI) |
p value |
|---|---|---|---|---|
| Sex | ||||
| F | Referent | |||
| M | 1.4 (0.9–2.2) | 0.16 | ||
| Age group, y | ||||
| 0–17 | 1.2 (0.5–2.8) | 0.71 | 1.3 (0.5–3.3) | 0.63 |
| 18–49 | Referent | Referent | ||
| 50–64 | 1.2 (0.6–2.3) | 0.65 | 1.6 (0.7–3.8) | 0.29 |
| 65–79 | 1.7 (0.9–3.2) | 0.13 | 1.7 (0.8–3.8) | 0.16 |
| ≥80 | 1.1 (0.5–2.1) | 0.90 | 1.1 (0.5–2.6) | 0.84 |
| Ethnicity | ||||
| Non-Hispanic | Referent | |||
| Hispanic | 2.4 (0.5–10.4) | 0.25 | ||
| Residence type | ||||
| Private | Referent | Referent | ||
| Long-term care or nursing facility | 0.7 (0.4–1.4) | 0.37 | 0.7 (0.3–1.5) | 0.33 |
| Correctional facility | 1.2 (0.1–9.7) | 0.90 | 1.9 (0.1–36.7) | 0.67 |
| Homeless | 1.5 (0.2–12.5) | 0.69 | 0.7 (0.1–4.8) | 0.74 |
| Underlying conditions | ||||
| Diabetes | 0.9 (0.5–1.5) | 0.68 | ||
| Heart disease: congestive heart failure or coronary artery disease | 1.3 (0.7–2.3) | 0.46 | ||
| Obesity | 1.3 (0.7–2.4) | 0.49 | 1.2 (0.6–2.5) | 0.58 |
| Chronic kidney disease or failure | 1.6 (0.7–3.6) | 0.30 | ||
| Chronic obstructive pulmonary disease | 0.8 (0.4–1.8) | 0.62 | ||
| Cancer | 2.4 (0.7–7.9) | 0.17 | ||
| Immunosuppression | 2.0 (0.5–8.6) | 0.37 | ||
| Hepatitis C or chronic liver disease | 1.5 (0.4–6.9) | 0.57 | ||
| Other‡ | 2.3 (0.3–18.2) | 0.42 | ||
| Any underlying condition | 0.9 (0.5–1.7) | 0.75 | ||
| Other risk factors | ||||
| Skin injury | 1.0 (0.6–1.7) | 0.97 | ||
| Cigarette smoking | 0.9 (0.5–1.9) | 0.82 | ||
| Alcohol abuse | 0.9 (0.3–2.3) | 0.75 | ||
| Injection drug use | 3.4 (0.2–60.0) | 0.40 | 3.2 (0.2–63.0) | 0.45 |
Table 2. Individual risk factor and multivariable analysis of risk factors comparing invasive group A Streptococcus cases during 2014–2019 with cases from the 2008–2013 baseline period, Idaho, USA
*Standard logistic regression analysis performed unless otherwise noted. An odds ratio >1 indicates higher odds of being in the 2014–2019 period. †Firth logistic regression used to account for separation attributable to limited sample size and highly predictive risk factors. For multivariable analysis, results for residence type and injection drug use represent total effect and results for age group and obesity represent direct effect. ‡Other underlying conditions include paralysis, neurologic conditions, and developmental delay.
|
Type of infection or clinical syndrome |
No. (%) patients |
p value‡ |
||
|---|---|---|---|---|
|
Overall, N = 476† |
2008–2013, n = 82† |
2014–2019, n = 394 |
||
| Bacteremia without focus§ | 163 (34.2) | 34 (41.5) | 129 (32.7) | 0.13 |
| Cellulitis | 197 (41.4) | 30 (36.6) | 167 (42.4) | 0.33 |
| Pneumonia | 80 (16.8) | 15 (18.3) | 65 (16.5) | 0.69 |
| Streptococcal toxic shock syndrome | 25 (5.3) | 0 (0.0) | 25 (6.4) | 0.02 |
| Septic arthritis | 24 (5.0) | 6 (7.3) | 18 (4.6) | 0.30 |
| Empyema | 19 (4.0) | 4 (4.9) | 15 (3.8) | 0.65 |
| Necrotizing fasciitis | 12 (2.5) | 4 (4.9) | 8 (2.0) | 0.14 |
| Osteomyelitis | 6 (1.3) | 0 (0.0) | 6 (1.5) | 0.26 |
| Meningitis | 4 (0.8) | 0 (0.0) | 4 (1.0) | 0.36 |
| Other¶ | 3 (0.6) | 1 (1.2) | 2 (0.5) | 0.46 |
Table 3. Clinical syndromes of invasive group A Streptococcus disease, overall and by 6-year periods, Idaho, USA, 2008–2019*
*Cases can have >1 type of infection or clinical syndrome. †Excludes 7 cases with missing data on type of infection or clinical syndrome, all during 2008–2013. ‡By χ2 test. §Group A Streptococcus isolated from blood, with no other clinical syndrome identified. ¶Other includes abscess, epiglottitis, and pelvic inflammatory disease.
|
Risk factor |
No. (%) patients |
||
|---|---|---|---|
|
Overall, N = 432* |
2008–2013, n = 69* |
2014–2019, n = 363* |
|
| Any underlying condition | |||
| No | 113 (26.2) | 17 (24.6) | 96 (26.5) |
| Yes | 319 (73.8) | 52 (75.4) | 267 (73.6) |
| Condition | |||
| Diabetes | 178 (41.2) | 30 (43.5) | 148 (40.8) |
| Heart disease: congestive heart failure or coronary artery disease | 116 (26.9) | 16 (23.2) | 100 (27.6) |
| Obesity | 95 (22.0) | 13 (18.8) | 82 (22.6) |
| Kidney disease: chronic kidney disease or chronic kidney failure | 61 (14.1) | 7 (10) | 54 (14.9) |
| Chronic obstructive pulmonary disease or emphysema | 43 (10.0) | 8 (11.6) | 35 (9.6) |
| Cancer | 38 (8.8) | 3 (4.3) | 35 (9.6) |
| Immunosuppression | 22 (5.1) | 2 (2.9) | 20 (5.5) |
| Hepatitis C or chronic liver disease | 18 (4.2) | 2 (2.9) | 16 (4.4) |
| Other† | 13 (3.0) | 1 (1.4) | 12 (3.3) |
| Total underlying conditions | |||
| 0 | 115 (26.6) | 17 (24.6) | 98 (27.0) |
| 1 | 113 (26.2) | 24 (34.8) | 89 (24.5) |
| 2 | 93 (21.5) | 10 (14.5) | 83 (22.9) |
| ≥3 | 111 (25.7) | 18 (26.1) | 93 (25.6) |
| Skin injury | |||
| Any skin injury | n = 412* | n = 70* | n = 342* |
| No | 211 (51.2) | 36 (51.4) | 175 (51.2) |
| Yes | 201 (47.8) | 34 (48.6) | 167 (48.8) |
| Type of skin injury‡ | n = 201 | n = 34 | n = 167 |
| Nonsurgical wound | 127 (63.2) | 22 (64.7) | 105 (62.9) |
| Surgical wound | 17 (8.5) | 3 (8.8) | 14 (8.4) |
| Trauma§ | 47 (23.4) | 8 (23.5) | 39 (23.4) |
| Burn | 2 (1.0) | 0 | 2 (1.2) |
| Skin breakdown | 3 (1.5) | 1 (2.9) | 2 (1.2) |
| Other | 5 (2.5) | 0 | 5 (3.0) |
| Behavioral risk factors | |||
| Current cigarette smoking¶ | n = 375* | n = 60* | n = 315* |
| No | 310 (82.7) | 49 (81.6) | 261 (82.9) |
| Yes | 65 (17.3) | 11 (18.3) | 54 (17.1) |
| Substance abuse | n = 386* | n = 63* | n = 323* |
| Alcohol abuse | 27 (7.0) | 5 (7.9) | 22 (6.8) |
| Methamphetamine use | 6 (1.6) | 0 | 6 (1.8) |
| Injection drug use | 8 (2.1) | 0 | 8 (2.5) |
| None of the above | 346 (89.6) | 58 (92.1) | 288 (89.2) |
| Other risk factors | n = 389* | n = 66* | n = 323* |
| GAS pharyngitis | 31 (8.0) | 7 (10.6) | 24 (7.4) |
| Household member with GAS | 8 (2.1) | 2 (3.0) | 6 (1.9) |
| Influenza | 12 (3.1) | 4 (6.1) | 8 (2.5) |
| None of the above | 336 (86.4) | 54 (81.8) | 282 (87.3) |
Table 4. Underlying conditions and risk factors of patients with invasive group A Streptococcus disease, overall and by 6-year periods, Idaho, 2008–2019
*Excludes missing data. †Other underlying conditions include paralysis, neurologic conditions, and developmental delay. ‡Data from 201 cases with a skin injury reported. §Cut, laceration, or puncture wounds. ¶Does not include e-cigarette use or vaping.
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During 2008–2019, a total of 483 cases of iGAS disease were reported among Idaho residents. Annual disease incidence per 100,000 persons increased from 1.04 to 4.76 during 2008–2019 (Figure 1). Case numbers were highest in January and lowest in August with similar patterns across years (Figure 2; Appendix Figure 1). We identified no changes in the surveillance system that might have led to increased case reporting. Overall, 52.8% of cases occurred among men; median age of case-patients was 62 years (Table 1). Data concerning race and ethnicity were available for 444 (91.9%) patients, most of whom were white, non-Hispanic persons (87.8%), followed by Hispanic (5.0%) and American Indian or Alaska Native persons (4.1%). For comparison, the 2018 population of Idaho was estimated to be 83.1% white non-Hispanic, 12.7% Hispanic, and 2.0% American Indian or Alaska Native[22]. The average annual incidence per 100,000 persons was 2.39 during 2008–2019; incidence was 2.55 among white non-Hispanic, 1.03 among Hispanic, and 5.19 among American Indian and Alaska Native persons. Data concerning residence type were available for 428 (88.6%) patients; most (349, 81.5%) resided in a private residence, followed by 63 (14.7%) in a LTCF or nursing home.
;)
EnlargeFigure 1. Annual number of reported cases of invasive group A Streptococcus (n = 483) and incidence (cases per 100,000 persons) from an investigation in Idaho, USA, comparing cases reported during 2014–2019 with cases from a lower-incidence baseline period, 2008–2013.
;)
EnlargeFigure 2. Seasonality of invasive group A Streptococcus (n = 483) by month of diagnosis, from an investigation in Idaho, USA, comparing cases reported during 2014–2019 with cases from a lower-incidence baseline period, 2008–2013.
Mean annual incidence per 100,000 persons was 0.94 during the 2008–2013 baseline period (n = 89 cases) and 3.84 during 2014–2019 (n = 394 cases). Patient demographics were similar between the periods (Table 1); we included odds ratios in risk factor analysis (Table 2). Disease incidence increased between periods among all age groups (Figure 3). The mean annual age-standardized incidence per 100,000 persons increased from 1.0 (95% CI 0.5–1.5) during 2008–2013 to 3.7 (95% CI 2.8–4.6) for 2014–2019. iGAS incidence increased in all 7 of Idaho’s public health districts (Appendix Figure 2).
;)
EnlargeFigure 3. Average annual incidence of invasive group A Streptococcus (cases per 100,000 persons) during 2008–2013 (n = 89) and 2014–2019 (n = 394), by age group, Idaho, USA. The fold change for 2014–2019 compared with 2008–2013 is shown for each age group above the paired columns.
Medical records were available for 383/483 (79.3%) cases, 62/89 (70%) during the baseline 2008–2013 period and 321/394 (81.5%) during 2014–2019. Information concerning deaths was available for 464 (96.0%) patients, 55 (11.9%) of whom died. The case-fatality rate was 14/84 (16.7%) for the baseline period and 41/380 (10.4%) during 2014–2019 (p = 0.132). Of 471 patients with data on hospitalization status, 441 (93.6%) were hospitalized. The proportion of patients hospitalized was slightly lower during 2008–2013 (88.4%, 76/86) compared with 94.8% (365/385) during 2014–2019 (p = 0.027). Data on length of hospital stay were available for 385 hospitalized patients. Median stay was 5 days (IQR 4–9) for all hospitalized patients: 5 days (IQR 3–8) for 58 patients hospitalized during 2008–2013 compared with 6 days (IQR 4–9; p = 0.118) for 327 patients hospitalized during 2014–2019.
Cellulitis was the most common clinical syndrome, reported in 41.4% of cases, followed by bacteremia without focus (34.2%) and pneumonia (16.8%) (Table 3). STSS, a rare but severe syndrome caused by GAS infection, was identified in 25 cases, all during 2014–2019 (p = 0.02). Toxic shock syndrome is a reportable disease in Idaho; however, 11 (44%) STSS cases were identified only retrospectively through medical record review. Ages of STSS patients ranged from 10 months to 82 years; 6/22 (27%) died (data missing for 3 patients). We observed no other differences in clinical syndromes between periods. GAS was cultured from blood in 92.9% (442/476) of cases, with no differences over time: 74/82 (90.2%) for the baseline period compared with 368/394 (93.4%; p = 0.31) during 2014–2019. Data on postpartum status were available for 47/50 women 15–44 years of age, 10/47 (21%) of whom were postpartum, with no difference between periods: 2/9 (22%) during the baseline period compared with 8/38 (21%; p = 0.94) during 2014–2019.
emm typing was conducted on bacterial isolates from 194 (40.2%) iGAS cases, 2/89 (2.3%) during 2008–2013 and 192/394 (48.7%) during 2014–2019. In total, we identified 38 different emm types; the most common were types 1 (n = 26, 13%), 12 (n = 25, 13%), 28 (n = 23, 12%), 11 (n = 15, 8%), and 4 (n = 15, 8%) (Figure 4; Appendix Table 1). emm typing results were available for 14/25 (56%) STSS cases, from which 10 emm types were observed; types 1 (n = 3), 12 (n = 2), and 1.25 (n = 2) were identified in >1 patient.
;)
EnlargeFigure 4. Invasive group A Streptococcus emm types (n = 194), Idaho, USA, 2012–2019, from an investigation in Idaho comparing invasive group A Streptococcus cases reported during 2014–2019 with cases from a lower-incidence baseline period, 2008–2013. The Idaho Bureau of Laboratories only began emm typing in 2014; 2012 data are from the Boise Veterans Administration Medical Center. Data for 2013 were unavailable.
Two outbreaks were previously identified on the basis of epidemiologic information and emm types. During July–September 2016, an outbreak of 5 cases of iGAS caused by emm59 occurred among residents of a single county. During 2014–2016, an outbreak of iGAS occurred among residents of a LTCF; 9 cases were emm11, and 4 cases did not have emm typing conducted. In addition, a household cluster of 2 cases, both associated with injection drug use, occurred in May 2015, but emm typing was not conducted. In total, 16/394 (4.1%) of cases during 2014–2019 were associated with a cluster or outbreak.
Information concerning underlying medical conditions was available for 432 (90.2%) patients, 69/89 (78%) during 2008–2013 and 363/394 (92.1%) during 2014–2019. Of these patients, 73.8% had ≥1 underlying condition; diabetes (41.2%), heart disease (26.9%), and obesity (22.0%) were the most common (Table 4). No patients had HIV infection. Overall, 201/412 (47.8%) patients had skin injuries, and nonsurgical wounds were most frequently reported. Injection drug use was reported for 8/386 (2.1%) and methamphetamine use for 6/386 (1.6%) patients, all during the 2014–2019 period. Data for other risk factors (GAS pharyngitis, household member with GAS infection, influenza infection) were available for 389 patients, and GAS pharyngitis was identified in 8.0% of patients. In regression analyses, we observed no associations between demographic or risk factors and the higher-incidence 2014–2019 period (Table 2). Injection drug use had an adjusted odds ratio of 3.2; however, the limited number of observations yielded wide 95% CIs.
