Showing papers by "Leo L.M. Poon published in 2003"

Isolation and characterization of viruses related to the SARS coronavirus from animals in southern China.

Abstract: A novel coronavirus (SCoV) is the etiological agent of severe acute respiratory syndrome (SARS). SCoV-like viruses were isolated from Himalayan palm civets found in a live-animal market in Guangdong, China. Evidence of virus infection was also detected in other animals (including a raccoon dog, Nyctereutes procyonoides) and in humans working at the same market. All the animal isolates retain a 29-nucleotide sequence that is not found in most human isolates. The detection of SCoV-like viruses in small, live wild mammals in a retail market indicates a route of interspecies transmission, although the natural reservoir is not known.

Characterization of H9 Subtype Influenza Viruses from the Ducks of Southern China: a Candidate for the Next Influenza Pandemic in Humans?

Abstract: A current view of the emergence of pandemic influenza viruses envisages a gene flow from the aquatic avian reservoir to humans via reassortment in pigs, the hypothetical “mixing vessel.” Understanding arising from recent H5N1 influenza outbreaks in Hong Kong since 1997 and the isolation of avian H9N2 virus from humans raises alternative options for the emergence of a new pandemic virus. Here we report that H9N2 influenza viruses established in terrestrial poultry in southern China are transmitted back to domestic ducks, in which the viruses generate multiple reassortants. These novel H9N2 viruses are double or even triple reassortants that have amino acid signatures in their hemagglutinin, indicating their potential to directly infect humans. Some of them contain gene segments that are closely related to those of A/Hong Kong/156/97 (H5N1/97, H5N1) or A/Quail/Hong Kong/G1/97 (G1-like, H9N2). More importantly, some of their internal genes are closely related to those of novel H5N1 viruses isolated during the outbreak in Hong Kong in 2001. This study reveals a two-way transmission of influenza virus between terrestrial and aquatic birds that facilitates the generation of novel reassortant H9N2 influenza viruses. Such reassortants may directly or indirectly play a role in the emergence of the next pandemic virus.

Evaluation of Reverse Transcription-PCR Assays for Rapid Diagnosis of Severe Acute Respiratory Syndrome Associated with a Novel Coronavirus

Abstract: The reverse transcription (RT)-PCR protocols of two World Health Organization (WHO) severe acute respiratory syndrome (SARS) network laboratories (WHO SARS network laboratories at The University of Hong Kong [WHO-HKU] and at the Bernhard-Nocht Institute in Hamburg, Germany [WHO-Hamburg]) were evaluated for rapid diagnosis of a novel coronavirus (CoV) associated with SARS in Hong Kong. A total of 303 clinical specimens were collected from 163 patients suspected to have SARS. The end point of both WHO-HKU and WHO-Hamburg RT-PCR assays was determined to be 0.1 50% tissue culture infective dose. Using seroconversion to CoV as the “gold standard” for SARS CoV diagnosis, WHO-HKU and WHO-Hamburg RT-PCR assays exhibited diagnostic sensitivities of 61 and 68% (nasopharyngeal aspirate specimens), 65 and 72% (throat swab specimens), 50 and 54% (urine specimens), and 58 and 63% (stool specimens), respectively, with an overall specificity of 100%. For patients confirmed to have SARS CoV and from whom two or more respiratory specimens were collected, testing the second specimen increased the sensitivity from 64 and 71% to 75 and 79% for the WHO-HKU and WHO-Hamburg RT-PCR assays, respectively. Testing more than one respiratory specimen will maximize the sensitivity of PCR assays for SARS CoV.

Rapid Diagnosis of a Coronavirus Associated with Severe Acute Respiratory Syndrome (SARS)

Abstract: Severe acute respiratory syndrome (SARS) is a recently emerged disease associated with pneumonia in infected patients (1). The disease is unusual in its severity, and patients suffering from this disease do not respond to empirical antimicrobial treatment for acute community-acquired typical or atypical pneumonia (2). By the end of March 2003, a cumulative total of 1622 cases and 58 deaths had been reported from 13 countries (3). The disease is highly infectious, and attach rates >56% have been reported in healthcare workers caring for SARS patients (2). Recently, we identified a novel virus in the family Coronaviridae in SARS patients (4). Of patients from whom paired acute and convalescent sera were available, all had seroconverted or had a greater than fourfold increase in antibody titer to this novel virus (4), suggesting that it plays an important role in the etiology of SARS. Thus, the establishment of a rapid noninvasive test for this virus is a high priority for monitoring and control of this disease. Here, we report a real-time quantitative PCR assay to detect this virus in clinical specimens. Patients with a clinical diagnosis of SARS and admitted in two hospitals in Hong Kong between February 26, 2003, and March 26, 2003, were considered for this study. Inclusion criteria were a fever of 38 °C or higher, cough or shortness of breath, new pulmonary infiltrate(s) on chest radiographs, and either a history of exposure to a patient with SARS or absence of response to empirical antimicrobial coverage for typical and atypical pneumonia. Samples were collected with informed consent. In total, 29 SARS patients with paired sera and nasopharyngeal aspirate (NPA) samples were available for the study. The diagnosis of SARS was confirmed in all patients by the presence of antibodies against the novel coronavirus in the serum (4). The …

Serial analysis of the plasma concentration of SARS coronavirus RNA in pediatric patients with severe acute respiratory syndrome.

Abstract: The recent identification of a novel coronavirus, SARS coronavirus (SARS-CoV), as an etiologic agent for severe acute respiratory syndrome (SARS) has prompted many groups to develop rapid and accurate molecular assays for the detection of this virus (1)(2)(3)(4). To date, most of the assays have focused predominantly on samples taken from nasopharyngeal aspirates, urine, and stools (5)(6). Although detection of SARS-CoV RNA in the plasma of SARS patients has been reported (1), the relatively low sensitivity of the ultracentrifugation-based approach for detecting SARS-CoV RNA in plasma has made this assay impractical. Recently we showed that a one-step real-time quantitative reverse transcription-PCR (RT-PCR) assay for the polymerase region of the SARS-CoV genome could detect viral RNA in 75–78% of nonultracentrifuged serum samples from adult SARS patients during the early stage of disease and that the serum SARS-CoV concentrations on admission were of prognostic significance (7). This finding demonstrates that plasma/serum SARS-CoV quantification may potentially be useful for the early diagnosis of SARS. Although most existing reports have focused on adult SARS patients, recent reports revealed that the clinical course was less severe in pediatric SARS patients than in adult SARS patients (8)(9). On the whole, the outcomes of pediatric SARS patients have been favorable. In this study, we investigated whether SARS-CoV RNA can be detected in the plasma samples of pediatric patients during different stages of SARS and studied the serial variation in viral loads. We quantified SARS-CoV RNA by real-time RT-PCR in the plasma of eight pediatric patients admitted to the New Territories East Cluster of Hospital Authority Hospitals in Hong Kong and who satisfied the WHO surveillance case definition for SARS (9). These patients were recruited between March 13, 2003, and May 17, 2003. Informed consent was obtained from …

The complete genome sequence of severe acute respiratory syndrome coronavirus strain HKU-39849 (HK-39).

Abstract: The complete genomic nucleotide sequence (29.7kb) of a Hong Kong severe acute respiratory syndrome (SARS) coronavirus (SARS-CoV) strain HK-39 is determined. Phylogenetic analysis of the genomic sequence reveals it to be a distinct member of the Coronaviridae family. 5' RACE assay confirms the presence of at least six subgenomic transcripts all containing the predicted intergenic sequences. Five open reading frames (ORFs), namely ORF1a, 1b, S, M, and N, are found to be homologues to other CoV members, and three more unknown ORFs (X1, X2, and X3) are unparalleled in all other known CoV species. Optimal alignment and computer analysis of the homologous ORFs has predicted the characteristic structural and functional domains on the putative genes. The overall nucleotides conservation of the homologous ORFs is low (<5%) compared with other known CoVs, implying that HK-39 is a newly emergent SARS-CoV phylogenetically distant from other known members. SimPlot analysis supports this finding, and also suggests that this novel virus is not a product of a recent recombinant from any of the known characterized CoVs. Together, these results confirm that HK-39 is a novel and distinct member of the Coronaviridae family, with unknown origin. The completion of the genomic sequence of the virus will assist in tracing its origin.

Reassortants of H5N1 Influenza Viruses Recently Isolated from Aquatic Poultry in Hong Kong SAR

Abstract: The H5N1 virus (H5N1/97) that caused the bird flu incident in Hong Kong in 1997 has not been isolated since the poultry slaughter in late 1997. But the donor of its H5 hemagglutinin gene, Goose/Guangdong/1/96-like (Gs/Gd/96-like) virus, established a distinct lineage and continued to circulate in geese in the area. In 2000, a virus from the Goose/Guangdong/1/96 lineage was isolated for the first time from domestic ducks. Subsequently, it has undergone reassortment, and these novel reassortants now appear to have replaced Gs/Gd/96-like viruses from its reservoir in geese and from ducks. The internal gene constellation is also different from H5N1/97, but these variants have the potential for further reassortment events that may allow the interspecies transmission of the virus.