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Table1.  

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.

Table2.  

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.

Table3.  

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.

Table4.  

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.

CME / ABIM MOC

Increasing Incidence of Invasive Group A Streptococcus Disease, Idaho, USA, 2008–2019

  • Authors: Eileen M. Dunne, PhD; Scott Hutton, PhD; Erin Peterson, BS; Anna J. Blackstock, PhD; Christine G. Hahn, MD; Kathryn Turner, PhD; Kris K. Carter, DVM
  • CME / ABIM MOC Released: 8/22/2022
  • THIS ACTIVITY HAS EXPIRED FOR CREDIT
  • Valid for credit through: 8/22/2023, 11:59 PM EST
Start Activity


Target Audience and Goal Statement

This activity is intended for infectious disease clinicians, internists, critical care clinicians, diabetologists, dermatologists, and other clinicians caring for patients with invasive group A Streptococcus infection.

The goal of this activity is for learners to be better able to describe the epidemiology of invasive group A Streptococcus in Idaho (where invasive group A Streptococcus is a reportable disease) during 2008 to 2019, based on a retrospective analytical study using surveillance data, emm typing results, and medical record review.

Upon completion of this activity, participants will:

  • Assess the epidemiology and clinical features of invasive group A Streptococcus and streptococcal toxic shock syndrome in Idaho during 2008 to 2019, based on a retrospective analytical study using surveillance data and medical record review
  • Evaluate emm typing results and potential risk factors for increased incidence in invasive group A Streptococcus, based on a comparison of cases reported during 2014 to 2019 with those from 2008 to 2013
  • Determine the clinical and public health implications of the epidemiology and clinical features of invasive group A Streptococcus in Idaho during 2008 to 2019, based on a retrospective analytical study using surveillance data and medical record review


Disclosures

Medscape, LLC requires every individual in a position to control educational content to disclose all financial relationships with ineligible companies that have occurred within the past 24 months. Ineligible companies are organizations whose primary business is producing, marketing, selling, re-selling, or distributing healthcare products used by or on patients.

All relevant financial relationships for anyone with the ability to control the content of this educational activity are listed below and have been mitigated. Others involved in the planning of this activity have no relevant financial relationships.


Faculty

  • Eileen M. Dunne, PhD

    Centers for Disease Control and Prevention
    Atlanta, Georgia
    Idaho Department of Health and Welfare
    Boise, Idaho

  • Scott Hutton, PhD

    Idaho Department of Health and Welfare
    Boise, Idaho

  • Erin Peterson, BS

    Idaho Department of Health and Welfare
    Boise, Idaho

  • Anna J. Blackstock, PhD

    Centers for Disease Control and Prevention
    Atlanta, Georgia

  • Christine G. Hahn, MD

    Idaho Department of Health and Welfare
    Boise, Idaho

  • Kathryn Turner, PhD

    Idaho Department of Health and Welfare
    Boise, Idaho

  • Kris K. Carter, DVM

    Centers for Disease Control and Prevention
    Atlanta, Georgia
    Idaho Department of Health and Welfare
    Boise, Idaho

CME Author

  • Laurie Barclay, MD

    Freelance writer and reviewer
    Medscape, LLC

    Disclosures

    Laurie Barclay, MD, has the following relevant financial relationships:
    Formerly owned stocks in: AbbVie

Editor

  • Tony Pearson-Clarke, MS

    Copyeditor 
    Emerging Infectious Diseases

Compliance Reviewer

  • Amanda Jett, PharmD, BCACP

    Associate Director, Accreditation and Compliance, Medscape, LLC

    Disclosures

    Amanda Jett, PharmD, BCACP, has no relevant financial relationships.


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CME / ABIM MOC

Increasing Incidence of Invasive Group A Streptococcus Disease, Idaho, USA, 2008–2019

Authors: Eileen M. Dunne, PhD; Scott Hutton, PhD; Erin Peterson, BS; Anna J. Blackstock, PhD; Christine G. Hahn, MD; Kathryn Turner, PhD; Kris K. Carter, DVMFaculty and Disclosures
THIS ACTIVITY HAS EXPIRED FOR CREDIT

CME / ABIM MOC Released: 8/22/2022

Valid for credit through: 8/22/2023, 11:59 PM EST

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Abstract and Introduction

Abstract

We investigated invasive group A Streptococcus epidemiology in Idaho, USA, during 2008–2019 using surveillance data, medical record review, and emm (M protein gene) typing results. Incidence increased from 1.04 to 4.76 cases/100,000 persons during 2008–2019. emm 1, 12, 28, 11, and 4 were the most common types, and 2 outbreaks were identified. We examined changes in distribution of clinical syndrome, patient demographics, and risk factors by comparing 2008–2013 baseline with 2014–2019 data. Incidence was higher among all age groups during 2014–2019. Streptococcal toxic shock syndrome increased from 0% to 6.4% of cases (p = 0.02). We identified no differences in distribution of demographic or risk factors between periods. Results indicated that invasive group A Streptococcus is increasing among the general population of Idaho. Ongoing surveillance of state-level invasive group A Streptococcus cases could help identify outbreaks, track regional trends in incidence, and monitor circulating emm types.

Introduction

Invasive group A Streptococcus (iGAS) disease is a severe bacterial infection caused by Streptococcus pyogenes, sometimes called strep A; ≈25,000 cases occurred in the United States in 2019[1]. iGAS disease is defined as illness associated with detection of group A Streptococcus in a normally sterile site, such as blood, pleural fluid, joint fluid, or deep tissue. iGAS has different clinical syndromes, including bacteremia without focus, pneumonia, and cellulitis, and severe manifestations, include necrotizing fasciitis and streptococcal toxic shock syndrome (STSS). The highly variable M protein, encoded by emm (M protein gene), is essential for virulence and serves as the primary target for epidemiologic typing of GAS[2]. Most patients with iGAS are hospitalized and the estimated case-fatality rate in the United States is 12%[3]. Numerous risk factors are associated with iGAS, including older age, diabetes, HIV infection, heart disease, cancer, obesity, injection drug use, long-term care facility (LTCF) residence, homelessness, preceding or concurrent influenza infection, and exposure to children with sore throats[4–9]. No licensed vaccines for GAS exist despite its substantial global disease burden: an estimated 1.78 million new cases of severe GAS (iGAS, acute rheumatic fever, rheumatic heart disease, and poststreptococcal glomerulonephritis) and 517,000 deaths occurring each year[10]. In 2019, the World Health Organization recognized GAS as a leading cause of infectious disease burden and proposed better characterization of GAS epidemiology as a priority activity for vaccine development[11].

During the past decade, iGAS incidence has increased in the United States, Canada, Ireland, Australia, and New Zealand[1,12–16]. Reasons for these increases are unclear but could include changing demographics (e.g., an aging population at higher risk for iGAS), rising prevalence of other risk factors associated with iGAS infection, or changes in circulating emm types. In some US states, iGAS outbreaks among specific populations (e.g., persons experiencing homelessness or who inject drugs) or the emergence of rarely occurring emm types were linked to increases in iGAS incidence[17–21]. In Idaho, a rural, western US state with a 2020 population of ≈1.8 million persons, iGAS is a reportable disease. We conducted a retrospective analytical study using surveillance data, emm typing results, and medical record review to describe the epidemiology of iGAS in Idaho during 2008–2019. In addition, we compared cases reported during 2014–2019 with cases from a lower-incidence 2008–2013 baseline period to determine whether clinical syndromes, patient demographics, and risk factors were associated with increased iGAS incidence.