SARS and common viral infections

In California, molecular testing was useful in decreasing suspicion for severe acute respiratory syndrome (SARS), by detecting common respiratory pathogens (influenza A/B, human metapneumovirus, picornavirus, Mycoplasma pneumoniae, Chlamydia spp., parainfluenza virus, respiratory syncytial virus, and adenovirus) in 23 (45%) of 51 patients with suspected SARS and 9 (47%) of 19 patients with probable SARS.

Severe acute respiratory syndrome coronavirus on hospital surfaces

Background. Health care workers continued to contract severe acute respiratory syndrome (SARS), even after barrier precautions were widely implemented.

Methods. We explored the possible contribution of contaminated hospital surfaces to SARS transmission by swabbing surfaces in 2 hospitals and testing the swab samples by reverse-transcriptase polymerase chain reaction (RT-PCR) and viral culture.

Results. Twenty-six of 94 swab samples tested positive for viral RNA. Swab samples of respiratory secretions from each of the 4 patients examined tested positive by RT-PCR, as were 12 of 43 swabs from patient rooms and 10 of 47 swabs from other parts of the hospital, including the computer mouses at 2 nursing stations and the handrail of the public elevator. Specimens from areas with patients with SARS in the most infectious phase of illness (days 5–15 after onset) were more likely to be RNA positive than were swab specimens from elsewhere (24 of 63 samples vs. 2 of 31 samples; P = .001). All cultures showed no growth.

Conclusions. Although the viruses identified may have been noninfectious, health care workers should be aware that SARS coronavirus can contaminate environmental surfaces in the hospital, and fomites should be considered to be a possible mode of transmission of SARS.

Prevalence of subclinical infection by the SARS coronavirus among general practitioners in Hong Kong

Eight general practitioners had severe acute respiratory distress syndrome (SARS) in Hong Kong during the epidemic, and others may have been infected by the SARS coronavirus without developing the full syndrome. We conducted a serological and questionnaire survey to determine the prevalence of subclinical infection by SARS coronavirus among general practitioners in Hong Kong. Participants had to be doctors actively practising in family medicine and who did not have SARS. Approximately 3200 general practitioners were invited to participate and the results of 574 were eligible for analysis. 29 samples were tested positive by enzyme-linked immunosorbent assay, but all these samples had titre < 25 by immunoflorescence assay. The prevalence for seropositivity was thus 0% (95% CI, 0.0%-0.6%). This finding documents the lack of subclinical infection by SARS coronavirus in an at-risk group in the community.

One-tube nested RT-PCR enabled by using a plastic film and its application for the rapid detection of SARS-virus

A general strategy based on the use of a plastic film that allows reverse transcription and nested-PCR in a single closed-tube has been developed. The reaction mixture for the second PCR amplification is quarantined in the cap of the reaction tube during the first round amplification by a piece of plastic film, and later introduced into the PCR amplicons from the first round reaction by centrifugation without opening the reaction tube. The main advantages of our method are its high sensitivity, specificity, simplicity, cost effectiveness, low risk of contamination and the ease in establishment of conditions for nested-PCR. The method has been successfully applied to the detection of the genomic RNA from SARS-CoV, the detection limit of this method is comparable to that of the conventional two-tube nested PCR system. This method could be easily adapted to the detection of other targets.

Organ distribution of severe acute respiratory syndrome (SARS) associated coronavirus (SARS-CoV) in SARS patients: implications for pathogenesis and virus transmission pathways

We previously identified the major pathological changes in the respiratory and immune systems of patients who died of severe acute respiratory syndrome (SARS) but gained little information on the organ distribution of SARS‐associated coronavirus (SARS‐CoV). In the present study, we used a murine monoclonal antibody specific for SARS‐CoV nucleoprotein, and probes specific for a SARS‐CoV RNA polymerase gene fragment, for immunohistochemistry and in situ hybridization, respectively, to detect SARS‐CoV systematically in tissues from patients who died of SARS. SARS‐CoV was found in lung, trachea/bronchus, stomach, small intestine, distal convoluted renal tubule, sweat gland, parathyroid, pituitary, pancreas, adrenal gland, liver and cerebrum, but was not detected in oesophagus, spleen, lymph node, bone marrow, heart, aorta, cerebellum, thyroid, testis, ovary, uterus or muscle. These results suggest that, in addition to the respiratory system, the gastrointestinal tract and other organs with detectable SARS‐CoV may also be targets of SARS‐CoV infection. The pathological changes in these organs may be caused directly by the cytopathic effect mediated by local replication of the SARS‐CoV; or indirectly as a result of systemic responses to respiratory failure or the harmful immune response induced by viral infection. In addition to viral spread through a respiratory route, SARS‐CoV in the intestinal tract, kidney and sweat glands may be excreted via faeces, urine and sweat, thereby leading to virus transmission. This study provides important information for understanding the pathogenesis of SARS‐CoV infection and sheds light on possible virus transmission pathways. This data will be useful for designing new strategies for prevention and treatment of SARS. Copyright © 2004 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Performance and Cost evaluation of one commercial and six in-house conventional and real-time reverse transcription-pcr assays for detection of severe acute respiratory syndrome coronavirus

We evaluated seven reverse transcription-PCR (RT-PCR) assays, including six in-house assays and one commercial assay for the detection of severe acute respiratory syndrome coronavirus (SARS-CoV) RNA in clinical specimens. RT-PCR assays targeted different genomic regions and included three conventional assays (one nested and two non-nested) run on a conventional heat block and four real-time assays performed in a LightCycler (LC; Roche Diagnostics). All in-house assays were optimized for assay parameters, including MgCl2, primer, and probe concentrations. The commercial assay was the RealArt HPA CoV RT-PCR assay (Artus), which was run in the LC. Testing serial dilutions of cultured SARS-CoV showed that the analytical sensitivity of the assays ranged from 10(-8) to 10(-6), corresponding to 1 and 100 copies of viral RNA, respectively. Significant differences in analytical sensitivities were observed between assays (P < 0.01, probit regression analysis for 50% sensitivity levels for the top two assays versus the others). Testing 68 clinical specimens (including 17 respiratory tract specimens, 29 urine samples, and 22 stools or rectal swabs) demonstrated that six of the seven assays detected at least 17 of 18 positives (defined as positive in at least two assays), and two of the assays had a sensitivity of 100%. There were no significant differences in sensitivity between the assays (P = 0.5 [Cochrance Q test, least sensitive 15 of 18 versus 18 of 18]). The specificities of the assays ranged from 94.0 to 100% without significant differences (P = 0.25 to 0.5 [McNemar test]). The reagent and technologist cost of performing the in-house PCR assays ranged from $5.46 to $9.81 Canadian dollars (CDN) per test. The commercial assay cost was considerably higher at $40.37 per test. The results demonstrated good performance for all assays, providing laboratories that need to do SARS RNA testing with a choice of assay formats.

A one step quantitative RT-PCR for detection of SARS coronavirus with an internal control for PCR inhibitors

In this study, we report a one step quantitative RT-PCR assay for severe acute respiratory syndrome (SARS) diagnosis. The overall detection rate for clinical samples collected from Days 1 to 9 of disease onset is 86.2% and the specificity of the assay is 100%. To detect false negative results due to PCR inhibitors or faulty RNA extraction, we have further modified this one step RT-PCR assay for simultaneous detection of severe acute respiratory syndrome (SARS) coronavirus (CoV) and 18S ribosomal RNA (rRNA) as an internal positive control.

SARS: responding to an unknown virus

The severe acute respiratory syndrome (SARS) is an emerging infection caused by a novel coronavirus which first appeared in southern China at the end of 2002. In early 2003, through a single incident, it spread to Hong Kong, Singapore, Canada and Vietnam. For busy clinicians in large public hospitals, the response to the virus was initially based on ensuring a high level of protection for staff. However, as the epidemic progressed and more information became available about the virus, procedures were rationalized and the virus is currently under control worldwide. There are, however, numerous unanswered questions concerning super-spreading events, the modes of transmission of the virus and, perhaps most importantly, the rapid detection of the virus early in the course of disease. These issues need to be addressed in case the virus becomes more widespread in the near future.

Development of Taqman RT-nested PCR system for clinical SARS-CoV detection

Severe acute respiratory syndrome (SARS) is an acute newly emerged infectious respiratory illness. The etiologic agent of SARS was named ‘SARS-associated coronavirus’ (SARS-CoV) that can be detected with reverse transcription-polymerase chain reaction (RT-PCR) assays. In this study, 12 sets of nested primers covering the SARS-CoV genome have been screened and showed sufficient sensitivity to detect SARS-CoV in RNA isolated from virus cultured in Vero 6 cells. To optimize further the reaction condition of those nested primers sets, seven sets of nested primers have been chosen to compare their reverse transcribed efficiency with specific and random primers, which is useful to combine RT with the first round of PCR into a one-step RT-PCR. Based on the sensitivity and simplicity of results, the no. 73 primer set was chosen as the candidate primer set for clinical diagnoses. To specify the amplicon to minimize false positive results, a Taqman RT-nested PCR system of no. 73 nested primer set was developed. Through investigations on a test panel of whole blood obtained from 30 SARS patients and 9 control persons, the specificity and sensitivity of the Taqman RT-nested PCR system was found to be 100 and 83%, respectively, which suggests that the method is a promising one to diagnose SARS in early stages.

Pregnancy and perinatal outcomes of women with severe acute respiratory syndrome

OBJECTIVE

This study was undertaken to evaluate the pregnancy and perinatal outcomes of pregnant women with severe acute respiratory syndrome (SARS).

STUDY DESIGN

All pregnant women (12) who presented with SARS in Hong Kong between February 1 and July 31, 2003, were included. The pregnancy and perinatal outcomes were collected. Evidence of perinatal transmission of virus was assessed with the SARS-associated coronavirus reverse-transcriptase polymerase chain reaction on cord blood, placenta tissue, and subsequent follow-up of the neonate on serology.

RESULTS

Three deaths occurred among the 12 patients, giving a case fatality rate of 25%. Four of the 7 patients (57%) who presented in the first trimester had spontaneous miscarriage. Four of the 5 patients who presented after 24 weeks were delivered preterm. Two mothers recovered without delivery, but their ongoing pregnancies were complicated by intrauterine growth restriction. No newborn infant had clinical SARS and all investigations were negative for SARS.

CONCLUSION

SARS during pregnancy is associated with high incidences of spontaneous miscarriage, preterm delivery, and intrauterine growth restriction. There is no evidence of perinatal SARS infection among infants born to these mothers.

[Detection of RNA of SARS coronavirus in hospital sewage]

OBJECTIVE

In order to explore the existence of SARS coronavirus (Co-V) and/or its RNA in sewage of hospitals administered SARS patients.

METHODS

A novel electropositive filter was used to concentrate the SARS-CoV from the sewage of two hospitals administered SARS patients in Beijing, including twelve 2,500 ml sewage samples from the hospitals before disinfection, and ten 25,000 ml samples after disinfection; as well as cell culture, RT-PCR and sequencing of gene to detect and identify the viruses from sewage.

RESULTS

There was no live SARS-CoV detected in the sewage in this study. The nucleic acid of SARS-CoV had been found in the 12 sewage samples before disinfection from both hospitals by semi-nested PCR. After disinfection, SARS-CoV RNA could only be detected from the samples from the 309th Hospital, and the others were negative.

CONCLUSION

It provides evidence that there is no live SARS-Cov in the sewage from hospitals with SARS patients though SARS-CoV RNA can be detected.

Human monoclonal antibody as prophylaxis for SARS coronavirus infection in ferrets

SARS coronavirus continues to cause sporadic cases of severe acute respiratory syndrome (SARS) in China. No active or passive immunoprophylaxis for disease induced by SARS coronavirus is available. We investigated prophylaxis of SARS coronavirus infection with a neutralising human monoclonal antibody in ferrets, which can be readily infected with the virus. Prophylactic administration of the monoclonal antibody at 10 mg/kg reduced replication of SARS coronavirus in the lungs of infected ferrets by 3.3 logs (95% CI 2.6-4.0 logs; p<0.001), completely prevented the development of SARS coronavirus-induced macroscopic lung pathology (p=0.013), and abolished shedding of virus in pharyngeal secretions. The data generated in this animal model show that administration of a human monoclonal antibody might offer a feasible and effective prophylaxis for the control of human SARS coronavirus infection.

Mucosal immunisation of African green monkeys (Cercopithecus aethiops) with an attenuated parainfluenza virus expressing the SARS coronavirus spike protein for the prevention of SARS

BACKGROUND

The outbreak of severe acute respiratory syndrome (SARS) in 2002 was caused by a previously unknown coronavirus-SARS coronavirus (SARS-CoV). We have developed an experimental SARS vaccine for direct immunisation of the respiratory tract, the major site of SARS- coronavirus transmission and disease.

METHODS

We expressed the complete SARS coronavirus envelope spike (S) protein from a recombinant attenuated parainfluenza virus (BHPIV3) that is being developed as a live attenuated, intranasal paediatric vaccine against human parainfluenza virus type 3 (HPIV3). We immunised eight African green monkeys, four with a single dose of BHPIV3/ SARS-S and four with a control, BHPIV3/Ctrl, administered via the respiratory tract. A SARS-coronavirus challenge was given to all monkeys 28 days after immunisation.

FINDINGS

Immunisation of animals with BHPIV3/SARS-S induced the production of SARS-coronavirus-neutralising serum antibodies, indicating that a systemic immune response resulted from mucosal immunisation. After challenge with SARS coronavirus, all monkeys in the control group shed SARS coronavirus, with shedding lasting 5-8 days. No viral shedding occurred in the group immunised with BHPIV3/SARS-S.

INTERPRETATION

A vectored mucosal vaccine expressing the SARS-coronavirus S protein alone may be highly effective in a single-dose format for the prevention of SARS.

[Quantitative detection of SARS-CoV RNA in excreta and oropharyngeal washing fluid from convalescence patients with severe acute respiratory syndrome]

OBJECTIVE

To detect the severe acute respiratory syndrome coronavirus (SARS-CoV) RNA in excreta and oropharyngeal washing fluid (OWF) from the convalescence SARS patients, and to determine whether convalescence patients carry the SARS-CoV, and whether having infectivity.

METHODS

Totally 531 samples (including urine, stool, and OWF) were collected from 177 convalescence patients with positive SARS antibody which were confirmed by ELISA method. Real-time quantitative PCR was performed to detect the RNA of the SARS-CoV, and results were analyzed by SPSS analysis software.

RESULTS

There were 49 (27.7%) cases of SARS-CoV RNA detection positive in 177 patients, including 31 (17.5%) cases with one sample positive, 14 (7.9%) cases with two samples positive, and 4 (2.3%) cases with three samples positive. The positive rates of urine, stool, and OWF were 14.7% (26/177), 11.9% (21/177), and 13.6% (24/177), respectively. The quantity of SARS-CoV RNA in samples was 100-47 000 copies/ml. No significant difference was found among urine, stool, and OWF on the difference grade quantity of SARS-CoV RNA quantity.

CONCLUSIONS

About 10% convalescence SARS patients might still carry the SARS-CoV in hospitalization. The detection of SARS-CoV RNA by real-time quantitative PCR may become a laboratory examination warranty for convalescence SARS patients to discharge hospital and relieve separation.

[Analysis on the risk factors of severe acute respiratory syndromes coronavirus infection in workers from animal markets]

OBJECTIVE

To investigate the possible risk factors of severe acute respiratory syndromes coronavirus (SARS-CoV) infection in workers from animal markets.

METHODS

Self-designed questionnaires were used and serum samples were tested. Logistic regression analysis was used to analyze the data.

RESULTS

Results from simple factor logistic regression analysis showed that jobs which dealing with domestic livestock, wild livestock, wild animals, aquatics were related to risk factors of SARS-CoV infection. Results from multifactor logistic regression analysis showed that jobs that dealing with wild livestock and poultry were important risk factors with OR 12.28 and 0.41.

CONCLUSION

Job that dealing with palm civets was the main risk factor of SARS-CoV infection in animal market workers.

Prophylactic and therapeutic effects of small interfering RNA targeting SARS-coronavirus

OBJECTIVES

To identify and characterize the siRNA duplexes that are effective for inhibition of SARS-CoV infection and replication in the non-human primate cells. This in vitro study will serve as the foundation for development of novel anti-SARS therapeutics.

METHODS

48 siRNA sequences were designed for targeting regions throughout entire SARS-CoV genome RNA including open-reading frames for several key proteins. Chemically synthesized siRNA duplexes were transfected into foetal rhesus kidney (FRhK-4) cells prior to or after SARS-CoV infection. The inhibitory effects of the siRNAs were evaluated for reductions of intracellular viral genome copy number and viral titres in the cell culture medium measured by Q-RT-PCR and CPE-based titration, respectively. Four siRNA duplexes were found to achieve potent inhibition of SARS-CoV infection and replication. A prolonged prophylactic effect of siRNA duplexes with up to 90% inhibition that lasted for at least 72 h was observed. Combination of active siRNA duplexes targeting different regions of the viral genome resulted in therapeutic activity of up to 80% inhibition.

CONCLUSION

Chemically synthesized siRNA duplexes targeting SARS-CoV genomic RNA are potent agents for inhibition of the viral infection and replication. The location effects of siRNAs were revealed at both genome sequence and open-reading frame levels. The rapid development of siRNA-based SARS-CoV inhibitors marked a novel approach for combating newly emergent infectious diseases.