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Notes: 1 Molecular epidemiological investigation of nosocomial outbreak of human 2 metapneumovirus in pediatric hemato-oncology patients 3 Sollip Kim
1, Heungsup Sung
1, Ho Joon Im
2, Soo-Jong Hong
2, and Mi-Na Kim
1* 4
Department of Laboratory Medicine1 and Pediatrics
2, University of Ulsan College of 5
Medicine and Asan Medical Center, Seoul, Korea 6 7 Running title: Nosocomial outbreak of hMPV 8 We do not have any conflict of interest relating to this article. 9 10 * Address for Correspondence 11 Mi-Na Kim, M.D., Ph.D. 12 Associate Professor, Department of Laboratory Medicine, University of Ulsan College 13 of Medicine and Asan Medical Center, Asanbyeongwon-gil 86, Songpa-gu, Seoul 138-14 736, Republic of Korea. Tel: +82.2.301044511, Fax: +82.2.4780884. E-mail: 15 [email protected] 16
Copyright © 2009, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.J. Clin. Microbiol. doi:10.1128/JCM.01959-08 JCM Accepts, published online ahead of print on 11 February 2009
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Abbreviation 1 Human metapneumovirus (hMPV) 2 Hospital-acquired hMPV infection (HA-hMPV) 3 Community-acquired hMPV infection (CA-hMPV) 4 Reverse transcriptase polymerase chain reaction (RT-PCR) 5 6 Number of words in the abstract: 90 (<50) 7 Number of words in the manuscript: 1084 (<1,000) 8
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Abstract 1 We report the first nosocomial outbreak of human metapneumovirus (hMPV) in 2 paediatric patients. Among 15 paediatric hMPV infections from March to May 2007, 3 there was a nosocomial outbreak involving two patients sharing a room with a 4 community-acquired case at hemato-oncology ward. The estimated incubation period 5 was 7-9 days in a symptomatic nosocomial case. Sequencing of fusion genes of 15 6 isolates revealed 2 clusters of A2 and 1 cluster of B2. Three isolates from the outbreak 7 had identical sequences belonging to A2-cluster. There was also a separate nosocomial 8 case in B2-cluster. 9 Keywords: Human metapneumovirus; Epidemiology; Nosocomial outbreak 10 on N
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Human metapneumovirus (hMPV), a recently discovered virus of the subfamily 1 Pneumovirinae, is a major cause of hospitalization of infants because of respiratory tract 2 infection (14). Transmission is likely to occur via direct contact and droplet, as with 3 respiratory syncytial virus (RSV) (12, 16). Although there are a few reports of 4 nosocomial hMPV infections involving infants (2, 6, 7), there have been no study of 5 hMPV outbreak in pediatric patients in an acute care hospital. Most outbreaks of hMPV 6 involve elderly patients in long-term care facilities and neuropsychiatry ward (1, 3, 9, 11, 7 12). The objective of this study was to characterize the epidemiology of a nosocomial 8 hMPV outbreak in pediatric patients. 9 We retrospectively investigated 15 pediatric patients whose nasopharyngeal aspirates 10 tested positive for hMPV by reverse transcriptase polymerase chain reaction (RT-PCR) 11 from March to May 2007 in a 2,200 bed-tertiary-care hospital. hMPV RT-PCR was 12 performed using the primer set of the Seeplex
TM RV Detection kit (Seegene, Seoul, 13
Korea), as described previously (15). All patients were negative for RSV, influenza 14 virus, parainfluenza virus, and adenovirus, as determined by direct antigen test, shell 15 vial culture, and RT-PCR. 460-bp sequences of the fusion (F) protein gene were aligned 16 with prototype hMPV strains using the ClustalW2 algorithm 17 (www.ebi.ac.uk/Tools/clustalw/). Phylogenetic trees were generated with the neighbor-18
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joining method and the Kimura 2-parameter substitution model using MEGA software 1 (ver. 4.0). 2 The median age of the 15 patients was 1.6 years (range, 0.3-7 years) and there were 11 3 males and 4 females. The clinical diagnoses attributed to hMPV included 10 cases of 4 pneumonia and 4 cases of bronchiolitis. Three patients had hospital-acquired hMPV 5 infections (HA-hMPV), designated as Asan-HA01, 02, and 03, and the other 12 patients 6 had community-acquired hMPV infections (CA-hMPV). 7 The sequences of F protein gene of hMPVs in our patients had 96-99% homology to 8 those of type strain published in the NCBI database. Four major hMPV lineages (A1, 9 A2, B1, and B2) have been described (17). Phylogenetic analysis classified 11 isolates 10 into subgroup A2, 1 isolate into subgroup B1, and 3 isolates into subgroup B2 (Fig 1). 11 The sequences of the 11 strains of subgroup A2 had nucleotide similarity of 94.8-100%. 12 There were two closely-related clusters in genogroup A2; cluster 1 of six isolates with 13 homology of 99-100% and cluster 2 of three isolates with homology of 98-99%. There 14 was also a cluster of 2 isolates found in subgroup B2. It is useful to analyze molecular 15 lineages of the isolates for certain period to provide more information about the 16 epidemiologic relationship of hMPV. 17 Cluster 1 included two HA-hMPV isolates and four CA-hMPV isolates. Among cluster 18
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1, two HA-hMPV patients shared a room with a CA-hMPV patient for 3 to 5 days 1 before hMPV was detected during their hospital stays (Fig. 2). The sequences of F 2 genes of all three isolates were identical, indicating that this CA-hMPV patient was the 3 index case. Even though index CA-hMPV case had fever, cough and sputum on 4 admission, a pneumonic consolidation was found on hospital day 4. Standard 5 precautions were kept during a hospital stay but not for preventing droplet transmissions. 6 Considering overlap period of their stay, the incubation period was 7 days at minimum 7 and 9 days at maximum in a symptomatic nosocomial case. They were all hemato-8 oncology patients; 2 acute myeloid leukemia and 1 hemophagocytic 9 lymphohistiocytosis. They all had fever and took blood and urine cultures at admission 10 but grew no microorganisms and Mycoplasma antibody tests performed at the time of 11 sampling for hMPV were all negative. After the index case was diagnosed to be positive 12 for hMPV infection, he was immediately discharged and those two nosocomial cases 13 sharing a room with him received hMPV tests and isolated together in same room. All 14 four CA-hMPV strains of cluster 1 were isolated for a one month period in April and 15 May 2007 from patients who lived in the neighborhood of our hospital. In Korea, the 16 peak season for hMPV is spring, rather than late winter (4, 10, 18). The first report that 17 described the lineage of hMPV isolates in Korea also showed a predominance of the A2 18
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lineage among the isolates obtained from 2003 to 2005 at an acute care hospital in Seoul 1 (5). A2 seemed to be a cause of community outbreak at that time and this time. These 2 findings suggested that the increase of CA-hMPV during the peak season is associated 3 with the risk of an outbreak in a hospital. All 3 patients belonging to cluster 2 had CA-4 hMPV (Fig 1). A case of HA-hMPV, Asan-HA03, of cluster 3 (Fig 1.) was 5 epidemiologically separate from a case of CA-hMPV, Asan-CA09, of same cluster and 6 any other patients in this study. 7 This is the first report of a nosocomial outbreak of hMPV among pediatric patients. The 8 first confirmed nosocomial case in pediatric patients was an infant who never left the 9 hospital after birth among 19 patients diagnosed in a single winter season at a tertiary 10 referral hospital (6). Another previous study described 3 HA-hMPV cases among a total 11 of 37 hMPV-infected patients during a full year period at a large tertiary-care pediatric 12 center (2). However all were separate cases without evidence of proven transmission. In 13 this study, a nosocomial oubreak occurred among the patients sharing a room for several 14 days. Therefore contact seemed to be needed to acquire hMPV infection. Nosocomial 15 outbreaks of RSV have been reported in pediatric wards, including neonatal intensive 16 care units (8, 13), but nosocomial outbreaks of hMPV are rarely reported at acute care 17 facilities. There are several reports of hMPV outbreaks among elderly patients 18
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institutionalized in long-term care facilities (1, 3, 11, 12). One previous study reported a 1 nosocomial outbreak of hMPV infection among elderly patients in a psychiatric ward 2 (3). These patients had attack rates of 56%, but only seven symptomatic patients had 3 RT-PCR confirmation of infection and all seven of these isolates were of the same 4 genotype. Another study of a large outbreak at a long-term care facility reported an 5 attack rate of 72%, as measured by frequency of respiratory symptoms, but only six 6 hMPV isolates were sequenced and classified into two clusters (1). Considering the high 7 attack rate of hMPV at institutional environments, emergence of nosocomial outbreak is 8 not surprising at paediatric wards in which patients of susceptible ages stay. 9 In conclusion, hMPV may be responsible for nosocomial outbreaks in pediatric patients 10 during the peak season of CA-hMPV. To prevent nosocomial outbreak of hMPV, early 11 diagnosis and prompt isolation are required for pediatric patients complaining of 12 respiratory symptoms especially in the season of community outbreak. 13
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1 Fig. 1. Phylogenetic analysis of fusion (F) gene fragments of human metapneumovirus 2 (hMPV) from 15 cases positive for hMPV by reverse transcriptase polymerase chain 3 reaction. The tree was constructed by neighbour joining method using the Kimura two-4 parameter model and bootstrap values were calculated from 1000 trees. The scale bar 5 indicated the estimated number of substitutions per 20 nucleotides. Shaded boxes 6 denote clusters; two clusters of subgroup A2 and one cluster of subgroup B2. 7 8 Fig 2. Chronological illustration of hospitalization and clinical and laboratory findings 9 of three patients involved in the nosocomial outbreak. Closed bar and striped bar 10 indicate the overlap periods of hospital stays between each of two HA-hMPV patients 11 and index CA-hMPV patient, respectively. Dotted bar indicates the isolation of two 12 nosocomial cases together in the same room. Respiratory symptoms of Asan-HA01 13 commenced at 9 days after start of overlap periods. AML, acute myeloid leukemia; 14 HLH, hemophagocytic lymphohistiocytosis; hMPV, human metapneumovirus, ER, 15 emergency room; PICU, paediatric intensive care unit. 16
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Asan-CA03
Apr 14
Asan-HA02Apr 30 May 3 May 16 May 23
ER PICU61 wardroom 33
61 ward room 5
Asan-HA01Apr 30 May 1 May 3 May 16 May 28 Aug 13
ER
61 wardroom 4
61 ward room 32
61 ward room 5
61 ward room 35
May 8
May 10
7/M, AML M2
4/F, AML M7
0.3/M, HLH
Negative for hMPV
at follow up test
Fever Fever, cough, rale
Pneumonic consolidation
Fever,
hepatosplenomegaly
Fever aggravation
Date of urine and blood culture
Date of specimens for hMPV, respiratory syncytial virus, influenza virus, parainfluenza virus, adenovirus and Mycoplasma antibody
Date of hMPV positive result
Apr 30 May 3 May 7
ER61 ward room 4
61 ward room 33
Apr 29
Fever, cough,
sputum
Cough aggravation
Pneumonic consolidation
Klebsiella pneumoniae
isolated for blood culture
*
*
*
*
Fig 2.
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