240


Jaeyoung Moon et al


Fig. 1. Phylogenetic analysis based on partial nucleotide sequences of M and S segments of severe fever with thrombocytopenia syndrome virus (SFTSV) strains using the maximum likelihood (ML) method and the Kimura 2-parameter model. Numbers on branches indicate bootstrap percentages based on 1,000 replications, and the scale bar indicates nucleotide substitutions per site. The index patient and case 1 are marked with closed circles.


showed leukopenia, thrombocytopenia, and elevated levels of aspartate transaminase, alanine transaminase, and creatine phosphokinase. On September 29, he rapidly deteriorated with hypersomnia and dis- orientation. He was transferred into the intensive care unit (ICU). On September 30, incidental epistaxis and oral bleeding appeared. The patient was intubated for mechanical ventilation following a seizure attack with hypoxemia. On October 1, he expired from progression of multiorgan failure. Confirmatory RT-PCR test revealed that he was positive for SFTSV, with 1.9×106 copies/mL of viral titer at admis- sion. During ICU hospitalization, standard and contact precautions were implemented with suspicion of SFTS. Epidemiologic investigation revealed that a total of 14 HCP


contacted the index patient during his hospitalization (Table 1). Of these, 2 were confirmed or suspected to have SFTS, including a 31-year-old male doctor who tried endotracheal intubation for the index patient (case 1) and a 26-year-old male mortuary beautician (case 2). Case 1 was admitted with fever of 39.3°C and chills on October 10. SFTS was confirmed by detecting SFTSV RNA (6.6×104 copies/mL) from his serum and ≥4-fold increase in antibody titers. He had short contact (within 10 minutes) with the index patient during endotracheal intubation, wearing a fluid- shield mask and gloves. During intubation, frequent oro-tracheal suctions were done to ensure visibility due to patient’s naso-oral bleeding. Case 2 had contact with the index corpse without gloves or mask. He felt malaise without documented fever 1 week after contact. He had a 2-fold increase in serial IgG titer from 1:128 to 1:256 in sera collected at 25 days and 60 days after contact, respectively, without detection of SFTSV RNA. He denied any


recent history of outdoor activity. The remaining 12 HCP were negative for SFTSV by IFA. PCR sequencing was performed for the index patient and case 1.


Sequences ofMand S segments from case 1 shared 100% nucleotide identities with the index patient. Phylogenetic analysis for sequences of M and S segments from the isolated virus were classified as genotype D and clustered with sequences of PCR products from case 1 and the index patient (Fig. 1).


Discussion


We have documented a cluster of nosocomial SFTS using epi- demiologic and viral genomic evidence. The index patient and case 1 were classified as genotype D, although genotype B strains of SFTS were predominant in Korea during 2013–2017.9 Genotype D was isolated from only 1 case in 2014. Both M and S segments showed 100% homology in nucleotide sequences, confirming the same origin of SFTS infection between the index patient and case 1. Epidemiological investigation showed that all HCP wore fluid- shield mask and gloves during potential exposure period. How- ever, these PPEs cannot protect conjunctiva or upper respiratory tract against aerosols containing the pathogen. Case 1 might be infected through aerosols generated from suctions of oral bleeding during endotracheal intubation. Previous studies reported that doctors contracted this disease after performing endotracheal intubation2,3,5 and suggested droplet or possible aerosol trans- mission.3,5 We believe that case 2 was infected through direct


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92  |  Page 93  |  Page 94  |  Page 95  |  Page 96  |  Page 97  |  Page 98  |  Page 99  |  Page 100  |  Page 101  |  Page 102  |  Page 103  |  Page 104  |  Page 105  |  Page 106  |  Page 107  |  Page 108  |  Page 109  |  Page 110  |  Page 111  |  Page 112  |  Page 113  |  Page 114  |  Page 115  |  Page 116  |  Page 117  |  Page 118  |  Page 119  |  Page 120  |  Page 121  |  Page 122  |  Page 123  |  Page 124  |  Page 125  |  Page 126  |  Page 127  |  Page 128  |  Page 129  |  Page 130  |  Page 131  |  Page 132  |  Page 133  |  Page 134  |  Page 135  |  Page 136  |  Page 137  |  Page 138  |  Page 139  |  Page 140  |  Page 141  |  Page 142  |  Page 143  |  Page 144  |  Page 145  |  Page 146  |  Page 147  |  Page 148  |  Page 149  |  Page 150  |  Page 151  |  Page 152  |  Page 153  |  Page 154  |  Page 155  |  Page 156