1126 infection control & hospital epidemiology october 2015, vol. 36, no. 10


figure 2. Hepatitis C virus (HCV) genetic fingerprinting results for genotype 2b from site B. Phylogenetic tree of genotype 2b HCV E1/E2 sequences from 1 case patient (Patient H, shaded), 2 proximate patients (Patient S and Patient D), and 3 non-related patients (PHRL patient 19 and 54 and AB661247 [a HCV genotype 2a sequence obtained from Genbank to serve as the root for the phylogenetic tree]). Single genome sequences (20–23 sequences per patient) were aligned with MUSCLE, and a neighbor-joining tree was created with MEGA software employing a Kimura 2-parameter distance model with 1000 bootstrap replications. Scale bar represents genetic distance (percent substitutions per nucleotide site).


sequences (>20 per patient) and phylogenetic tree construc- tion (using Geneious, version 7.1.3, software) were used to evaluate genetic relatedness between newly infected, proximal, and reference patient strains. Trees were created using Kimura 2-parameter distance matrix with 1,000 bootstrap replicates. Patient strains demonstrating less than 5% difference in nucleotide sequence were considered possibly related.


results


HBV,HCV, and HIV seropositivity prevalence for all patients at facilities A and B and exposed cohort patients is reported in Table 1. Among cohort patients with postexposure testing, comparisons with facility prevalence were lower for HBsAg at facility A (0 positive cohort patients vs 4.5 expected on the basis of facility prevalence [P=.02]), and lower with borderline sta- tistical significance at facility B (2 positive cohort patients vs 7.1 expected [P=.056]). HIV-1 Ab positivity was no different at facility A (2 cohort patients vs 1.64 expected [P=.98]), but higher at facility B (8 cohort patients vs 3.2 expected [P=.034]).


HCV Ab positivity in the exposed cohort was higher than expected at both facilities (41 vs 25.4 expected at facility A [P=.005], 59 vs 33.6 expected at facility B [P<.001]). A total of 718 and 1,073 patients were included in facility A


and B investigations, respectively. One patient was exposed at both facilities. Two hundred eighty-three previously known infections among 212 unique patients in the exposed cohort were identified at both facilities (15 HIV-1, 144 HCV, and 124 HBV) (Table 2). The one patient who was part of both cohorts was previously known to be positive forHBVand HCV, and he was counted once in the total cohort. Of known positive patients, many were coinfected (56 with HBV/HCV, 5 with HBV/HCV/HIV, 4 with HBV/HIV, and 1 with HCV/HIV). Sixty-eight viral infections among 67 patients were newly identified (1 patient had HBV and HCV) (Online Figures 1 and 2). This newly identified group was overwhelming male (65 [97%] of 67) and the median (range) age was 66 (39–94) years (Online Table 2). No new HIV-infected patients were identified at either facility. Of 63 newly identified HBV infections (either HBsAg


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