Publications by authors named "Yan'An Hou"

8 Publications

  • Page 1 of 1

Adequacy of public health communications on H7N9 and MERS in Singapore: insights from a community based cross-sectional study.

BMC Public Health 2018 04 2;18(1):436. Epub 2018 Apr 2.

Institute of Infectious Diseases and Epidemiology, Tan Tock Seng Hospital, Singapore, Singapore.

Background: Singapore remains vulnerable to worldwide epidemics due to high air traffic with other countries This study aims to measure the public's awareness of the Middle East Respiratory Syndrome (MERS) and Avian Influenza A (H7N9), identify population groups who are uninformed or misinformed about the diseases, understand their choice of outbreak information source, and assess the effectiveness of communication channels in Singapore.

Methods: A cross-sectional study, comprising of face-to-face interviews, was conducted between June and December 2013 to assess the public's awareness and knowledge of MERS and H7N9, including their choice of information source. Respondents were randomly selected and recruited from 3 existing cohort studies. An opportunistic sampling approach was also used to recruit new participants or members in the same household through referrals from existing participants.

Results: Out of 2969 participants, 53.2% and 79.4% were not aware of H7N9 and MERS respectively. Participants who were older and better educated were most likely to hear about the diseases. The mean total knowledge score was 9.2 (S.D ± 2.3) out of 20, and 5.9 (S.D ± 1.2) out of 10 for H7N9 and MERS respectively. Participants who were Chinese, more educated and older had better knowledge of the diseases. Television and radio were the primary sources of outbreak information regardless of socio-demographic factors.

Conclusion: Heightening education of infectious outbreaks through appropriate media to the young and less educated could increase awareness.
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April 2018

Infectious disease transmission: survey of contacts between hospital-based healthcare workers and working adults from the general population.

J Hosp Infect 2018 Apr 31;98(4):404-411. Epub 2017 Oct 31.

Saw Swee Hock School of Public Health, National University Health System, National University of Singapore, Singapore, Singapore; Department of Clinical Epidemiology, Tan Tock Seng Hospital, Singapore, Singapore. Electronic address:

Background: Healthcare workers (HCWs) may be the inadvertent interface between the healthcare setting and the community for infectious diseases transmission.

Aim: To investigate HCWs' contacts during a work day and compare these against working adults from the general population.

Methods: Prospective survey of contacts through 24 h self-reported diary in three public sector tertiary care hospitals and community-based working adults in Singapore. Participants were HCWs and working adults from the community.

Findings: In all, 211 HCWs and 1028 working adults reported a total of 4066 and 9206 contacts. HCWs reported more work-related contacts than community-based working adults (median of 13 versus 4), and more contacts that were neither household nor work-related (1 versus 0) but fewer household contacts (2 versus 3). HCWs reported more work-related contacts involving physical contacts, and more new contacts particularly with short duration (≤15 min) compared to community-based working adults. Among different HCW types, doctors reported the highest whereas ward-based nurses reported the lowest total work-related contacts. Around half of ward-based and clinic-based nurses' contacts involved physical touch. Work-related contacts reported by clinic-based nurses, doctors, and assorted HCWs were shorter than in ward-based nurses, with a substantial number effectively occurring with new contacts. Institutional effects significant on univariate analyses were much reduced and non-significant after adjusting for confounding by HCW type.

Conclusion: HCWs' contacts differ substantially from those of community-based working adults. HCWs may thus be at higher risk of acquiring and spreading contact-transmissible and respiratory infections due to the nature of their work. Whereas total number of contacts was fairly similar between HCW types, the characteristics of their contacts differed substantively.
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April 2018

Valine/isoleucine variants drive selective pressure in the VP1 sequence of EV-A71 enteroviruses.

BMC Infect Dis 2017 05 8;17(1):333. Epub 2017 May 8.

Cirad, UMR 17, Intertryp, TA-A17/G, Campus International de Baillarguet, 34398, Montpellier Cedex 5, France.

Background: In 2011-2012, Northern Vietnam experienced its first large scale hand foot and mouth disease (HFMD) epidemic. In 2011, a major HFMD epidemic was also reported in South Vietnam with fatal cases. This 2011-2012 outbreak was the first one to occur in North Vietnam providing grounds to study the etiology, origin and dynamic of the disease. We report here the analysis of the VP1 gene of strains isolated throughout North Vietnam during the 2011-2012 outbreak and before.

Methods: The VP1 gene of 106 EV-A71 isolates from North Vietnam and 2 from Central Vietnam were sequenced. Sequence alignments were analyzed at the nucleic acid and protein level. Gene polymorphism was also analyzed. A Factorial Correspondence Analysis was performed to correlate amino acid mutations with clinical parameters.

Results: The sequences were distributed into four phylogenetic clusters. Three clusters corresponded to the subgenogroup C4 and the last one corresponded to the subgenogroup C5. Each cluster displayed different polymorphism characteristics. Proteins were highly conserved but three sites bearing only Isoleucine (I) or Valine (V) were characterized. The isoleucine/valine variability matched the clusters. Spatiotemporal analysis of the I/V variants showed that all variants which emerged in 2011 and then in 2012 were not the same but were all present in the region prior to the 2011-2012 outbreak. Some correlation was found between certain I/V variants and ethnicity and severity.

Conclusions: The 2011-2012 outbreak was not caused by an exogenous strain coming from South Vietnam or elsewhere but by strains already present and circulating at low level in North Vietnam. However, what triggered the outbreak remains unclear. A selective pressure is applied on I/V variants which matches the genetic clusters. I/V variants were shown on other viruses to correlate with pathogenicity. This should be investigated in EV-A71. I/V variants are an easy and efficient way to survey and identify circulating EV-A71 strains.
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May 2017

Tuberculous meningitis is a major cause of mortality and morbidity in adults with central nervous system infections in Kota Kinabalu, Sabah, Malaysia: an observational study.

BMC Infect Dis 2016 06 16;16:296. Epub 2016 Jun 16.

Menzies School of Health Research, Darwin, Australia.

Background: Central nervous system (CNS) infections are a significant contributor to morbidity and mortality globally. However, most published studies have been conducted in developed countries where the epidemiology and aetiology differ significantly from less developed areas. Additionally, there may be regional differences due to variation in the socio-economic levels, public health services and vaccination policies. Currently, no prospective studies have been conducted in Sabah, East Malaysia to define the epidemiology and aetiology of CNS infections. A better understanding of these is essential for the development of local guidelines for diagnosis and management.

Methods: We conducted a prospective observational cohort study in patients aged 12 years and older with suspected central nervous system infections at Queen Elizabeth Hospital, Kota Kinabalu, Sabah, Malaysia between February 2012 and March 2013. Cerebrospinal fluid was sent for microscopy, biochemistry, bacterial and mycobacterial cultures, Mycobacterium tuberculosis polymerase chain reaction (PCR), and multiplex and MassCode PCR for various viral and bacterial pathogens.

Results: A total of 84 patients with clinically suspected meningitis and encephalitis were enrolled. An aetiological agent was confirmed in 37/84 (44 %) of the patients. The most common diagnoses were tuberculous meningitis (TBM) (41/84, 48.8 %) and cryptococcal meningoencephalitis (14/84, 16.6 %). Mycobacterium tuberculosis was confirmed in 13/41 (31.7 %) clinically diagnosed TBM patients by cerebrospinal fluid PCR or culture. The acute case fatality rate during hospital admission was 16/84 (19 %) in all patients, 4/43 (9 %) in non-TBM, and 12/41 (29 %) in TBM patients respectively (p = 0.02).

Conclusion: TBM is the most common cause of CNS infection in patients aged 12 years or older in Kota Kinabalu, Sabah, Malaysia and is associated with high mortality and morbidity. Further studies are required to improve the management and outcome of TBM.
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June 2016

Efficacy and safety of celgosivir in patients with dengue fever (CELADEN): a phase 1b, randomised, double-blind, placebo-controlled, proof-of-concept trial.

Lancet Infect Dis 2014 Aug 28;14(8):706-715. Epub 2014 May 28.

Program in Emerging Infectious Diseases, Duke-NUS Graduate Medical School, Singapore, Singapore. Electronic address:

Background: Dengue infection is the most common mosquito-borne viral disease worldwide, but no suitable antiviral drugs are available. We tested the α-glucosidase inhibitor celgosivir as a treatment for acute dengue fever.

Methods: To establish eligibility for inclusion in a phase 1b, randomised, double-blind, placebo-controlled, proof-of-concept trial, individuals aged 21-65 years who had had a fever (≥38°C) for less than 48 h, met at least two criteria indicating probable dengue infection, and had a positive result on a dengue point-of-care test kit or PCR assay were referred for screening at a centre in Singapore between July 30, 2012, and March 4, 2013. Using a web-based system, we randomly assigned patients who met full inclusion criteria after screening (1:1; random permuted block length four) to celgosivir (initial 400 mg loading dose within 6 h of randomisation, followed by 200 mg every 12 h for a total of nine doses) or matched placebo. Patients and the entire study team were masked to group assignment. The primary endpoints were mean virological log reduction (VLR) from baseline for days 2, 3, and 4, and area under the fever curve (AUC) for a temperature above 37°C from 0 h to 96 h. Efficacy analyses were by intention to treat. This study is registered with, number NCT01619969.

Findings: We screened 69 patients and randomly assigned 50 (24 to celgosivir, 26 to placebo). Mean VLR was greater in the celgosivir group (-1·86, SD 1·07) than in the placebo group (-1·64, 0·75), but the difference was non-significant (-0·22, 90% CI -0·65 to 0·22; one-sided p=0·203). The mean AUC was also higher in the celgosivir group (54·92, SD 31·04) than in the placebo group (40·72, 18·69), but again the difference was non-significant (14·20, 90% CI 2·16-26·25; one-sided p=0·973). We noted similar incidences of adverse events between groups.

Interpretation: Although generally safe and well tolerated, celgosivir does not seem to reduce viral load or fever burden in patients with dengue.

Funding: STOP Dengue Translational Clinical Research.
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August 2014

Chikungunya as a cause of acute febrile illness in southern Sri Lanka.

PLoS One 2013 2;8(12):e82259. Epub 2013 Dec 2.

Division of Medical Microbiology, Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America ; Hubert-Yeargan Center for Global Health, Durham, North Carolina, United States of America.

Background: Chikungunya virus (CHIKV) re-emerged in Sri Lanka in late 2006 after a 40-year hiatus. We sought to identify and characterize acute chikungunya infection (CHIK) in patients presenting with acute undifferentiated febrile illness in unstudied rural and semi-urban southern Sri Lanka in 2007.

Methodology/principal Findings: We enrolled febrile patients ≥ 2 years of age, collected uniform epidemiologic and clinical data, and obtained serum samples for serology, virus isolation, and real-time reverse-transcriptase PCR (RT-PCR). Serology on paired acute and convalescent samples identified acute chikungunya infection in 3.5% (28/797) patients without acute dengue virus (DENV) infection, 64.3% (18/28) of which were confirmed by viral isolation and/or real-time RT-PCR. No CHIKV/DENV co-infections were detected among 54 patients with confirmed acute DENV. Sequencing of the E1 coding region of six temporally distinct CHIKV isolates (April through October 2007) showed that all isolates posessed the E1-226A residue and were most closely related to Sri Lankan and Indian isolates from the same time period. Except for more frequent and persistent musculoskeletal symptoms, acute chikungunya infections mimicked DENV and other acute febrile illnesses. Only 12/797 (1.5%) patients had serological evidence of past chikungunya infection.

Conclusions/significance: Our findings suggest CHIKV is a prominent cause of non-specific acute febrile illness in southern Sri Lanka.
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February 2015

Exploring the origin and potential for spread of the 2013 dengue outbreak in Luanda, Angola.

Glob Health Action 2013 Aug 2;6:21822. Epub 2013 Aug 2.

Program in Emerging Infectious Diseases, Duke-NUS, Singapore.

Introduction: Dengue in Africa is underreported. Simultaneous reports of travellers with dengue returning from Luanda, Angola, to six countries on four continents suggest that a major dengue outbreak is currently occurring in Angola, South West Africa.

Methods: To identify the origin of the imported dengue virus, we sequenced the virus from Angola and investigated the interconnectivity via air travel between dengue-endemic countries and Angola.

Results And Conclusion: Our analyses show that the Angola outbreak was most likely caused by an endemic virus strain that had been circulating in West Africa for many years. We also show that Portugal and South Africa are most likely at the highest risk of importation of dengue from Angola due to the large number of air passengers between Angola and these countries.
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August 2013

Successful clearance of human parainfluenza virus type 2 viraemia with intravenous ribavirin and immunoglobulin in a patient with acute myocarditis.

J Clin Virol 2013 Jan 6;56(1):37-40. Epub 2012 Nov 6.

Department of Infectious Diseases, Singapore General Hospital, Singapore.

Human parainfluenza virus (HPIV) infection as an aetiology of acute viral myocarditis is rare, with only few cases reported in the literature to date. Here we report a case of fulminant HPIV-2 myocarditis in a 47 year-old man with viraemia who was successfully treated with intravenous ribavirin and intravenous immunoglobulin (IVIG). There are currently no recommendations on the treatment of HPIV myocarditis. We are, to our knowledge, the first to report a patient with a documented HPIV-2 viraemia that subsequently cleared after the initiation of antiviral therapy. Although it is difficult to definitively attribute the patient's clinical improvement to ribavirin or IVIG alone, our case does suggest that clinicians may wish to consider initiating ribavirin and IVIG in patients with HPIV myocarditis and persistent viraemia not responding to supportive measures alone.
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January 2013