Epidemiology of IGAS. Allison McGeer, MSc, MD, FRCPC Mount Sinai Hospital University of Toronto

Transcription

1 Epidemiology of IGAS Allison McGeer, MSc, MD, FRCPC Mount Sinai Hospital University of Toronto

2 Epidemiology of IGAS Median age: 48 years (range 0-101) 15% children (<16), 33% older adults (>65) 54% male 62% with chronic underlying illness 18% with cardiac disease, 14% lung disease, 11% diabetes, 10% cancer, 9% alcohol abuse 11% nosocomial, 7% from nursing homes 3.6% homeless 2.5% with recognized contact with another case of GAS infection

3 Epidemiology of IGAS 70% with positive blood cultures 30% other sterile site (eg. synovial fluid, pleural fluid, tissue) 50% skin/soft tissue infections, 16% primary bacteremia, 12% pneumonia, 10% arthritis 15% with STSS 8-10% with necrotizing fasciitis 26% required ICU admission (17% vented) 32% required surgery 18% died

4 Risk factors for IGAS in children Risk factor Cases Controls Odds ratio P value # rooms in house (mean) 1 other child in house 1 person with runny nose New use NSAIDS (.51,.88) (87%) 43 (57%) 17 (3.9,73) (11%) 26 (34%).09 (.01,.4) (24%) 7 (9%) 11 (2.1,55).005 Factor, EID, July 2005

5 Risk factors for IGAS in adults Risk factor Odds ratio P value Exposure to children with sore throat 4.9 (1.2,20).02 Number of persons in household 2.7 (1.4,5.3).004 IV drug use 15 (2.5,86).003 HIV infection 15 (1.0,207).004 Diabetes, cardiac disease, corticosteroid therapy, cancer 2.2 to

6 Rate per 100,000 population per year Invasive GAS disease Metropolitan Toronto/Peel Region, Non-STSS STSS

7 Number of invasive infections Number of episodes of igas due to M type 3 Metropolitan Toronto/Peel region

8 Number of cases Number of episodes of NF per year Metropolitan Toronto/Peel region *

9 Number of cases Number of episodes of STSS per year Metropolitan Toronto/Peel region *

10 Percentate of all strains igas, Toronto/Peel, Most common Mtypes different serotypes represented 13.6% of strains non-typeable M 1 M 12 M 3 M 28 M 4 M 89 M 5 M 11

11 Martin JM et al. NEJM 2002;;346:

12 0 Annualized rate per 100, Large IGAS outbreak in Thunder Bay & District Cases 2007/ Confirmed Group A Streptococcal Disease Thunder Bay District Health Unit, 1995/96 to Long-term care facility outbreak Expected: 6 Actual: 53 Rate 2007/08 (per 100,000) Expected: 3.6 Actual: 34.1 Rate ratio: 9.4 times baseline rate season (July-June) cases Annualized rate per 100,000

13 Feb Apr Jun Aug Oct Dec Feb Apr Jun Aug Oct Dec Feb Apr Jun Aug Oct Dec Feb Apr Jun Aug Oct Dec Feb Apr Jun Aug Oct number of cases Movement of emm-59 across Canada PQ ON MN SK AB BC Graph courtesy of Dr. Greg Tyrrell, National Centre for Streptococcus date

14 Risk estimates Risk of invasive disease normally: ~3 per 100,000 this outbreak: ~3 per 10,000 close contacts of invasive: ~3 per 1000 some clusters: 6/13 = 46%!!! Risk factors for these clusters: aboriginal, injection drug use, alcoholism low SES, under-housed chronic illnesses

15 What are the potential opportunities for prevention? Household contacts Combined circulation of chickenpox and group A streptococci in daycare Hospitals Nursing homes

16 Risk of secondary disease Rate invasive disease/100,000 household contacts UK US (2) US (1) Ontario

17 Summative results household contact 11 subsequent invasive cases 6 husband-wife pairs 1 pair brothers 1 father-daughter (2 months) 3 maternal-neonatal pairs (all British) Estimated risk 11/4748, or 1 per 430 household contacts

18 Does prophylaxis work? Household contacts of pharyngitis cases randomized to: placebo vs. penicillin vs. cephalosporin Rate of disease 5.3% (26/492) placebo 4.3% (19/447) amoxicillin 1.8% (9/507) cephalosporin (P=.003) 5 days of prophylaxis more effective than 3 or 4 Kikuta PIDJ 2007;26:139-41

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20 Percent macrolide resistant Macrolide resistance in invasive GAS, Ontario,

21 Can GAS be transmitted from patients to HCWs? Obviously, yes 2 cases of GAS STSS in HCWs in published literature 0/228 HCWs colonized with strain after caring for a patient with invasive disease in the ED So, less than 2% compared to household contacts: ~10% colonized; invasive disease in % No occupationally acquired invasive group A streptococcal disease in HCWs in Ontario over 12 years

22 Percent with second invasive case Can GAS be transmitted from patients to other patients and HCWs? Secondary cases of igas in Ontario, / /367 1/1551 NF + ICU Other diagnosis, ICU Non-ICU Daneman Clin Infect Dis 2005; 41:334 42

23 Transmission of igas from patients with community acquired disease Ontario GAS study 3 NF+ ICU, 1 pneumonia + ICU, 1 bacteremia Case reports 5 NF + ICU, 2 pneumonia + ICU

24 Hospitals 10% of hospital-acquired cases are part of outbreaks Most (70%) outbreaks only 2 cases Median time between cases= 4.5 days Two types of transmission By healthcare workers with illness/asymptomatic carriage DURING SURGICAL PROCEDURES From patient to patient on hands of staff Daneman Ann Int Med 2007;147:234

25 Nosocomial GAS, Ontario /291 (9.3%) cases of invasive GAS disease associated with at least one other GAS infection Time dependent: given 1 noso case 1 week: 4.2% chance of 2 nd case (50% related) 1 month: 6.3% chance 3 months: 12% chance 6 months: 24% chance No cases >1 week apart were related Daneman, CID: 2005;41:334-42

26 Are two nosocomial cases related? % <1 week: 8/12 cases linked >1 week: 0/96 cases linked <1 week 1wk - 1mo 1-3mos 3-6mos 6-12mos Time from Initial Nosocomial Case percent of nosocomial invasive GAS cases followed by another case within the same hospital percent of paired cases that represent true linked cases

27 Invasive GAS disease, LTCFs Ontario: 6% of all igas is in LTCFs 25% (6/24) index cases linked to outbreaks) Minnesota 7% of all igas is in LTCFs 13% (13/100) index cases linked to outbreaks 2 cases in one nursing home within 12 months were identical by PFGE in 86% of cases (93% in 3 months)

28 Invasive GAS disease, LTCFs NF 14% Other 3% Soft tissue 44% Bacteremia 18% Pneumonia 21%

29 Ontario outbreaks 41/122 cases (34%) associated with outbreaks Outbreak cases - no difference in age, gender, site of infection, M type of isolates Stable distribution over time Outbreaks more likely Dec-March OR 3.6 (95% CL 1.5, 8.8) Jordan Clin Infect Dis. 2007;45(6):742

30 Number of cases Seasonal distribution of LTCF cases No outbreak Outbreak J F M A M J J A S O N D Month

31 Characteristics of GAS outbreaks in nursing homes skin infections predominate insidious (3-4 excess infections per 100 residents per month, most minor) all residents affected 3-12% of residents colonized; fewer staff

32 Nursing home outbreaks in Ontario, Number (%) residents infected Number (%) residents colonized Number (%) staff colonized A (125 beds) 12 (9.5%) 6 (4.6%) 3/85 (3.5%) B (57 beds) 4 (6.9%) 6 (1.1%) 0/28 C (110 beds) 5 (4.6%) 3 (2.7%) 0/23 D (60 beds) 2 (2.3%) 3 (5%) 0/10 E (88 beds) 11 (13%) 10 (11%) 3/85 (3.5%)

33 Case #1 You get a report of a case of necrotizing fasciitis in a 52yo man who has been admitted to the ICU of your local hospital

34 Case #2 It is January, and the middle of influenza season. You get a report of an invasive GAS case in a 97yo resident of a nursing home; her admitting diagnosis is pneumonia. What do you do?

35 So, what do you do? Look for other cases by lab results Look for skin infections in last 30 days on same unit (expect rate 1-3 per 100 residents per month) Ask about family and visitors of resident

36 Control of GAS transmission, LTC Watch for infections - culture conjunctivitis, cellulitis (throat), pharyngitis Throat or nasal and skin lesion swabs of residents and patient care staff Treat positives, follow to ensure cleared Type strains

37 When you get a nosocomial case: Are there other cases? check lab for GAS isolates in last month ask about cellulitis, IV site infections on unit Ask relevant MDs/clinics about skin/soft tissue infections Hold isolate for typing, ask lab to call if any more isolates Is this transmission from a community acquired case? Is there a HCW who was ill who cared for this patient? Is this a surgical/obstetrical case? Could a colonized HCW be responsible?