Detection of severe acute respiratory syndrome coronavirus in blood of infected patients

Prevalence and clinical relevance of viraemia in viral respiratory tract infections: a systematic review

In this Review, we analysed the prevalence of viraemia during infection with SARS-CoV-2 and other relevant respiratory viruses, including other human coronaviruses such as MERS-CoV and SARS-CoV, adenovirus, human metapneumovirus, human rhinovirus/enterovirus, influenza A and B virus, parainfluenza virus, and respiratory syncytial virus. First, a preliminary systematic search was conducted to identify articles published before May 23, 2024 that reported on viraemia during infection with respiratory viruses. The articles were then analysed for relevant terms to identify the prevalence of viraemia, its association with the disease severity and long-term consequences, and host responses. A total of 202 articles were included in the final study. The pooled prevalence of viraemia was 34% for SARS-CoV-2 and between 6% and 65% for other viruses. Association of viraemia with disease severity was extensively reported for SARS-CoV-2 and also for SARS-CoV, MERS-CoV, adenoviruses, rhinoviruses, respiratory syncytial virus, and influenza A(H1N1)pdm09 (albeit with low evidence). SARS-CoV-2 viraemia was linked to memory problems and worsened quality of life. Viraemia was associated with signatures denoting dysregulated host responses. In conclusion, the high prevalence of viraemia and its association with disease severity suggests that viraemia could be a relevant pathophysiological event with important translational implications in respiratory viral infections.

Highly Prevalent SARS-CoV-2 Antigenemia in COVID-19 Patients

Background

Many issues, such as severity assessment and antibody responses, remain to be answered eagerly for evaluation and understanding of COVID-19. Immune lesion is one of key pathogenesis of the disease. It would be helpful to understand the disease if an investigation on antigenemia and association was conducted in the patients with SARS-CoV-2 infection.

Methods

A total of 156 patients admitted to the First People's Hospital of Hefei or Anhui Provincial Hospital on January to February 2020 were involved in this study. SARS-CoV-2 nucleocapsid (NP) antigen, specific IgM/IgG antibodies, and RNA were detected in sequential sera from three COVID-19 patients, and additional 153 COVID-19 patients by means of NP-antigen capture enzyme-linked immunosorbent assay, colloidal gold quick diagnosis, and real-time RT-PCR, respectively. The clinical types of COVID-19 patients were classified into asymptomatic, mild, moderate, severe, and critical, following on the Chinese guideline of COVID-19 diagnosis and treatment. The demographic and clinical data of patients were obtained for comparable analysis.

Results

NP antigen was detected in 5 of 20 sequential sera collected from three COVID-19 patients with typically clinical symptoms, and 60.13% (92/153) expanded samples collected within 17 days after illness onset. No SARS-CoV-2 RNA segment was detected in these sera. The NP positive proportion reached a peak (84.85%, 28/33) on 6 to 8 days after illness onset. Both NP concentration and positive proportion were increased with the increase of clinical severity of COVID-19. Compared to NP negative patients, NP positive patients had older age [years, medians (interquartile ranges (IQR)), 49 (6) vs. 31 (11)], lower positive proportion of NP specific IgM [27.17% (25/92) vs. 59.02% (36/61)], and IgG [21.74% (20/92) vs. 59.02% (36/61)] antibodies, and longer duration [days, medians (IQR), 24 (10) vs. 21 (13)] from illness to recovery.

Conclusions

SARS-CoV-2 NP antigenemia occurred in COVID-19, and presented highly prevalent at early stage of the disease. The antigenemia was related to clinical severity of the disease, and may be responsible for the delay of detectable SARS-Cov-2 IgM.

Microsampling: A role to play in Covid-19 diagnosis, surveillance, treatment and clinical trials

The outbreak of the new coronavirus disease changed the world upside down. Every day, millions of people were subjected to diagnostic testing for Covid-19, all over the world. Molecular tests helped in the diagnosis of current infection by detecting the presence of viral genome whereas serological tests helped in detecting the presence of antibody in blood as well as contributed to vaccine development. This testing helped in understanding the immunogenicity, community prevalence, geographical spread and conditions post-infection. However, with the contagious nature of the virus, biological specimen sampling involved the risk of transmission and spread of infection. Clinic or pathology visit was the most concerning part. Trained personnel and resources was another barrier. In this scenario, microsampling played an important role due to its most important advantage of remote, contactless, small volume and self-sampling. Minimum requirements for sample storage and ease of shipment added value in this situation. The highly sensitive instruments and validated assay formats assured the accuracy of results and stability of samples. Microsampling techniques are contributing effectively to the Covid-19 pandemic by reducing the demand for clinical staff in population-level testing. The validated and established applications supported the use of microsampling in diagnosis, therapeutic drug monitoring, development of treatment or vaccines and clinical trials for Covid-19.

High Frequency of SARS-CoV-2 RNAemia and Association With Severe Disease

Background

Detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA in blood, also known as RNAemia, has been reported, but its prognostic implications are poorly understood. This study aimed to determine the frequency of SARS-CoV-2 RNA in plasma and its association with coronavirus disease 2019 (COVID-19) clinical severity.

Methods

An analytical cross-sectional study was performed in a single-center tertiary care institution and included consecutive inpatients and outpatients with confirmed COVID-19. The prevalence of SARS CoV-2 RNAemia and the strength of its association with clinical severity variables were examined and included intensive care unit (ICU) admission, invasive mechanical ventilation, and 30-day all-cause mortality.

Results

Paired nasopharyngeal and plasma samples were included from 85 patients. The median age was 55 years, and individuals with RNAemia were older than those with undetectable SARS-CoV-2 RNA in plasma (63 vs 50 years; P = .04). Comorbidities were frequent including obesity (37.6%), hypertension (30.6%), and diabetes mellitus (22.4%). RNAemia was detected in 28/85 (32.9%) of patients, including 22/28 (78.6%) who required hospitalization. In models adjusted for age, RNAemia was detected more frequently in individuals who developed severe disease including ICU admission (32.1 vs 14.0%; P = .04) and invasive mechanical ventilation (21.4% vs 3.5%; P = .02). All 4 deaths occurred in individuals with detectable RNAemia. An additional 121 plasma samples from 28 individuals with RNAemia were assessed longitudinally, and RNA was detected for a maximum duration of 10 days.

Conclusions

This study demonstrated a high proportion of SARS-CoV-2 RNAemia, and an association between RNAemia and clinical severity suggesting the potential utility of plasma viral testing as a prognostic indicator for COVID-19.

Cardiorenal Tissues Express SARS-CoV-2 Entry Genes and Basigin (BSG/CD147) Increases With Age in Endothelial Cells

Vascular and cardiovascular inflammation and thrombosis occur in patients with severe coronavirus disease-2019 (COVID-19). Advancing age is the most significant risk factor for severe COVID-19. Using transcriptomic databases, the authors found that: 1) cardiovascular tissues and endothelial cells express putative genes for severe acute respiratory syndrome coronavirus-2 infection, including angiotensin-converting enzyme 2 (ACE2) and basigin (BSG); 2) severe acute respiratory syndrome coronavirus-2 receptor pathways ACE2/transmembrane serine protease 2 and BSG/peptidylprolyl isomerase B(A) polarize to lung/epithelium and vessel/endothelium, respectively; 3) expression of host genes is relatively stable with age; and 4) notable exceptions are ACE2, which decreases with age in some tissues, and BSG, which increases with age in endothelial cells, suggesting that BSG expression in the vasculature may explain the heightened risk for severe disease with age.

IVF laboratory COVID-19 pandemic response plan: a roadmap

BACKGROUND

The potential of COVID-19 severe pandemic necessitates the development of an organized and well-reasoned plan for the management of embryology/andrology laboratories while safeguarding the wellbeing of patients and IVF staff.

MAIN BODY

A COVID-19 pandemic response plan was proposed for embryology and andrology laboratories for pre-pandemic preparedness and pandemic management in anticipation of a possible second coronavirus wave. Preparation involves many plans and logistics before a pandemic risk rises. Many operational changes can be considered during the pandemic. This plan includes logistical arrangements, reducing labor needs, conserving supplies, and protective measures for embryologists and gametes/embryos.

CONCLUSION

The unpredictable emergence of the COVID-19 pandemic dictates the need for a preparedness plan for embryology/andrology laboratories, which includes an action-oriented plan to secure the safety of all stakeholders.

Detection and Isolation of SARS-CoV-2 in Serum, Urine, and Stool Specimens of COVID-19 Patients from the Republic of Korea

Objectives

Coronavirus Disease-19 (COVID-19) is a respiratory infection characterized by the main symptoms of pneumonia and fever. It is caused by the novel coronavirus severe acute respiratory syndrome Coronavirus-2 (SARS-CoV-2), which is known to spread via respiratory droplets. We aimed to determine the rate and likelihood of SARS-CoV-2 transmission from COVID-19 patients through non-respiratory routes.

Methods

Serum, urine, and stool samples were collected from 74 hospitalized patients diagnosed with COVID-19 based on the detection of SARS-CoV-2 in respiratory samples. The SARS-CoV-2 RNA genome was extracted from each specimen and real-time reverse transcription polymerase chain reaction performed. CaCo-2 cells were inoculated with the specimens containing the SARS-COV-2 genome, and subcultured for virus isolation. After culturing, viral replication in the cell supernatant was assessed.

Results

Of the samples collected from 74 COVID-19 patients, SARS-CoV-2 was detected in 15 serum, urine, or stool samples. The virus detection rate in the serum, urine, and stool samples were 2.8% (9/323), 0.8% (2/247), and 10.1% (13/129), and the mean viral load was 1,210 ± 1,861, 79 ± 30, and 3,176 ± 7,208 copy/μL, respectively. However, the SARS-CoV-2 was not isolated by the culture method from the samples that tested positive for the SARS-CoV-2 gene.

Conclusion

While the virus remained detectable in the respiratory samples of COVID-19 patients for several days after hospitalization, its detection in the serum, urine, and stool samples was intermittent. Since the virus could not be isolated from the SARS-COV-2-positive samples, the risk of viral transmission via stool and urine is expected to be low.

A Comprehensive Updated Review on SARS-CoV-2 and COVID-19

This literature review aims to provide a comprehensive current summary of the pathogenesis, clinical features, disease course, host immune responses, and current investigational antiviral and immunomodulatory pharmacotherapies to facilitate the development of future therapies and measures for prevention and control.

Estimation of the number of blood donors during the COVID-19 incubation period across China and analysis of prevention and control measures for blood transfusion transmission

BACKGROUND

The aim of this study was to estimate the number of blood donors during the COVID‐19 incubation period across China.

STUDY DESIGN AND METHODS

In this study, we developed a predictive model to estimate the number of blood donors during the COVID‐19 incubation period among 34 provincial regions in China. Our main assumption was that blood donors of all ages in different regions have a stable blood donation intention and the same infection risk.

RESULTS

First, we estimated the number of blood donors during the COVID‐19 incubation period in Wuhan city, Hubei Province, and China, from December 31, 2019 to March 17, 2020. Second, we compared the number of blood donors during the COVID‐19 incubation period in all provinces across China. In addition, we found that if all RBCs, plasma, and cryoprecipitation were stored in isolation until the 14th day, the potential risk of SARS‐CoV‐2 transmission through blood transfusion was reduced by at least 65.77% after the blood donor safely passed the COVID‐19 incubation period. Moreover, if the detection of SARS‐CoV‐2 RNA was carried out on all platelets, the potential risk would be reduced by 77.48%.

CONCLUSIONS

Although the risk is low, with the rapid spread of the COVID‐19 and the appearance of alarmingly high infectivity and a high fatality rate, appropriate measures should be taken by health departments to ensure the safety of clinical blood.

The Emergence of Zoonotic Pathogens as Agents of Concern in Transfusion Medicine

A variety of emerging infections are of interest to transfusion medicine clinicians, but zoonotic pathogens, those maintained in nonhuman hosts and transmitted to humans, have dominated recent discussions, especially emerging acute viral infections that can or might spread around a shrinking globe with unprecedented speed, in an infected human or an infected vector or reservoir host. Further, advanced pathogen discovery techniques (e.g., metagenomics) allow the identification of potential pathogens before their recognition as clinically relevant to transfusion medicine. In the aftermath of our experiences with HIV and posttransfusion hepatitis, our windows for response to such agents and infections have contracted rapidly. These characteristics pose difficult challenges for our development of surveillance and control regimes capable of timely, but appropriately nuanced, responses. This monograph surveys a selection of such agents, exploring their apparent relevance to transfusion medicine, closing with a framework for an ongoing approach to their surveillance, recognition, threat evaluation, and mitigation.

Find the right sample: A study on the versatility of saliva and urine samples for the diagnosis of emerging viruses

BACKGROUND

The emergence of different viral infections during the last decades like dengue, West Nile, SARS, chikungunya, MERS-CoV, Ebola, Zika and Yellow Fever raised some questions on quickness and reliability of laboratory diagnostic tests for verification of suspected cases. Since sampling of blood requires medically trained personal and comprises some risks for the patient as well as for the health care personal, the sampling by non-invasive methods (e.g. saliva and/ or urine) might be a very valuable alternative for investigating a diseased patient.

MAIN BODY

To analyse the usefulness of alternative non-invasive samples for the diagnosis of emerging infectious viral diseases, a literature search was performed on PubMed for alternative sampling for these viral infections. In total, 711 papers of potential relevance were found, of which we have included 128 in this review.

CONCLUSIONS

Considering the experience using non-invasive sampling for the diagnostic of emerging viral diseases, it seems important to perform an investigation using alternative samples for routine diagnostics. Moreover, during an outbreak situation, evaluation of appropriate sampling and further processing for laboratory analysis on various diagnostic platforms are very crucial. This will help to achieve optimal diagnostic results for a good and reliable case identification.

Specific serology for emerging human coronaviruses by protein microarray

We present a serological assay for the specific detection of IgM and IgG antibodies against the emerging human coronavirus hCoV-EMC and the SARS-CoV based on protein microarray technology. The assay uses the S1 receptor-binding subunit of the spike protein of hCoV-EMC and SARS-CoV as antigens. The assay has been validated extensively using putative cross-reacting sera of patient cohorts exposed to the four common hCoVs and sera from convalescent patients infected with hCoV-EMC or SARS-CoV.

A self-assembled fusion protein-based surface plasmon resonance biosensor for rapid diagnosis of severe acute respiratory syndrome

A surface plasmon resonance (SPR)-based biosensor was developed for simple diagnosis of severe acute respiratory syndrome (SARS) using a protein created by genetically fusing gold binding polypeptides (GBPs) to a SARS coronaviral surface antigen (SCVme). The GBP domain of the fusion protein serves as an anchoring component onto the gold surface, exploiting the gold binding affinity of the domain, whereas the SCVme domain is a recognition element for anti-SCVme antibody, the target analyte in this study. SPR analysis indicated the fusion protein simply and strongly self-immobilized onto the gold surface, through GBP, without surface chemical modification, offering a stable and specific sensing platform for anti-SCVme detection. AFM and SPR imaging analyses demonstrated that anti-SCVme specifically bound to the fusion protein immobilized onto the gold-micropatterned chip, implying that appropriate orientation of bound fusion protein by GBP resulted in optimal exposure of the SCVme domain to the assay solution, resulting in efficient capture of anti-SCVme antibody. The best packing density of the fusion protein onto the SPR chip was achieved at the concentration of 10 μg mL⁻¹; this density showed the highest detection response (906 RU) for anti-SCVme. The fusion protein-coated SPR chip at the best packing density had a lower limit of detection of 200 ng mL⁻¹ anti-SCVme within 10 min and also allowed selective detection of anti-SCVme with significantly low responses for non-specific mouse IgG at all tested concentrations. The fusion protein provides a simple and effective method for construction of SPR sensing platforms permitting sensitive and selective detection of anti-SCVme antibody.

Theoretically estimated risk of severe acute respiratory syndrome transmission through blood transfusion during an epidemic in Shenzhen, Guangdong, China in 2003

BACKGROUND

Severe acute respiratory syndrome (SARS) is a newly recognized infectious disease that caused an outbreak in south China in 2003. The cause of SARS was identified as a novel coronavirus (CoV). The existence of asymptomatic seroconvertors and the detection of the SARS-CoV RNA in plasma during the course of infection all suggest that SARS could, as least theoretically, be transmitted by transfusion. An estimate of the risk of SARS transmission through blood transfusion will contribute to decisions concerning blood safety monitoring and may be useful in the design of strategies to decrease the risk of transfusion-transmitted infections.

STUDY DESIGN AND METHODS

Case onset dates from the 2003 Shenzhen SARS epidemic and investigational results from Taiwan on viremia in humans are used to estimate the number of cases that were viremic throughout the epidemic. Estimates of the asymptomatic-to-clinically confirmed SARS-CoV infection ratio, the proportion of asymptomatic infections reported in a seroprevalence survey in Hongkong, and the population size of Shenzhen are used to infer the SARS-CoV transfusion-transmission risk. Statistical resampling methods are used.

RESULTS

Based on data from Shenzhen, Hongkong and Taiwan, the maximum and mean risk (per million) of SARS-CoV transmission from donors in Shenzhen were estimated as 23.57 (95% CI: 6.83-47.69) and 14.11 (95% CI: 11.00-17.22), respectively. The estimated risk peaked on April 02, 2003.

CONCLUSIONS

Although there are currently no confirmed reports of the transmission of SARS-CoV from asymptomatic individuals, recent research data indicate that transfusion-transmitted SARS-CoV is at least theoretically possible. Although the risk is low, with its rapid spread of the disease, appearance of alarmingly high infectivity and high fatality rate, public health authorities need to consider strategies for blood donor recruitment and virus inactivation during an epidemic to further ensure blood safety.

Using patient-collected clinical samples and sera to detect and quantify the severe acute respiratory syndrome coronavirus (SARS-CoV)

Background

Severe acute respiratory syndrome (SARS) caused a large outbreak of pneumonia in Beijing, China, in 2003. Reverse transcriptase polymerase chain reaction (RT-PCR) was used to detect and quantify SARS-CoV in 934 sera and self-collected throat washes and fecal samples from 271 patients with laboratory-confirmed SARS managed at a single institution.

Results

SARS-CoV detection rates in sera were highest in the first 9 days of illness, whereas detection was highest in throat washes 5–14 days after onset of symptoms. The highest SARS-CoV RT-PCR rates (70.4–86.3%) and viral loads (log₁₀ 4.5–6.1) were seen in fecal samples collected 2–4 weeks after the onset of clinical illness. Fecal samples were frequently SARS-CoV RT-PCR positive beyond 40 days, and occasional sera still had SARS-CoV detected after 3 weeks of illness.

Conclusion

In the context of an extensive outbreak with major pressure on hospital resources, patient self-collected samples are an alternative to nasopharyngeal aspirates for laboratory confirmation of SARS-CoV infection.

Pathogen inactivation and removal procedures used in the production of intravenous immunoglobulins

Patients with immunodeficiencies or some types of autoimmune diseases rely on a safe therapy with intravenous immunoglobulins (IVIGs) manufactured from human plasma, the only available source for this therapeutic. Since plasma is predisposed to contamination by a variety of blood-borne pathogens, ascertaining and ensuring the pathogen safety of plasma-derived therapeutics is a priority among manufacturers. State-of-the-art manufacturing processes provide a high safety standard by incorporating virus elimination procedures into the manufacturing process. Based on their mechanism these procedures are grouped into three classes: partitioning, inactivation, and virusfiltration.

Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV)

Severe acute respiratory syndrome (SARS) is caused by a coronavirus (CoV), SARSCoV. SARS-CoV belongs to the family Coronaviridae, which are enveloped RNA viruses in the order Nidovirales. Global research efforts are continuing to increase the understanding of the virus, the pathogenesis of the disease it causes (SARS), and the “heterogeneity of individual infectiousness” as well as shedding light on how to prepare for other emerging viral diseases. Promising drugs and vaccines have been identified. The milestones achieved have resulted from a truly international effort. Molecular studies dissected the adaptation of this virus as it jumped from an intermediary animal, the civet, to humans, thus providing valuable insights into processes of molecular emergence.

Clinical and Laboratory Findings of SARS in Singapore

Introduction: Singapore was one of 29 countries worldwide affected by severe acute respiratory syndrome (SARS) in 2003. Materials and Methods: There were 238 cases identified during the outbreak. We performed a retrospective analysis of the clinical and laboratory data of 234 patients admitted to Tan Tock Seng Hospital and Singapore General Hospital. Results: The mean age of patients was 21 years, 31.6% of patients were males and 41.8% were healthcare workers. At presentation, the common symptoms were fever, myalgia, cough and headache; rhinorrhoea was uncommon. On admission, 21% had leukopenia, 18% had thrombocytopaenia, 29% had hyponatraemia, 31% had hypokalaemia, 21% had transaminitis. Polymerase chain reaction (PCR) testing of respiratory and stool samples provided the best yield at the end of the first week of illness. Thirty-two patients were initially not recognised as probable SARS and were reclassified when the serology test results were available. The chief reasons for not identifying these patients early were persistently normal chest X-rays (68.8%), very mild presentation (43.8%) and the presence of a concomitant illness (12.5%). Overall, 12% of the patients were probable SARS with atypical presentations. Overall mortality was 11.8%. Conclusion: Patients infected with the SARS coronavirus had a wide clinical presentation with non-specific symptoms.

SARS in Singapore – Predictors of Disease Severity

Introduction: Severe acute respiratory syndrome (SARS) affected 8096 individuals in 29 countries, with 774 deaths. In Singapore, there were 238 cases of SARS with 33 deaths. A retrospective analysis was performed to identify predictors of poor outcome in patients with SARS locally. Materials and Methods: Clinical, laboratory and outcome data of 234 patients admitted to Tan Tock Seng Hospital and Singapore General Hospital were collected and analysed. Only data collected at the time of admission were used in the analysis for predictors of poor outcome. Adverse events were defined as admission to the intensive care unit or death. Results: Clinical (temperature, FiO2) and laboratory [leukocyte, lymphocyte, neutrophil, platelet, lactate dehydrogenase (LDH), albumin] trends in groups with and without an adversarial event were presented. Fifty patients experienced an adverse event. On univariate analysis, male gender, advanced age, presence of comorbidities, neutrophilia, lymphopaenia, hyponatraemia, hypoalbuminaemia, transaminitis and elevated LDH or C-reactive protein were found to be significant predictors. On multivariate analysis, predictors of poor outcome were increased age [odds ratio (OR) 1.73 for every 10-year increase; 95% CI, 1.35 to 2.21], neutrophilia (OR 1.06 for every 1x109 /L increase; 95% CI, 1.02 to 1.11) and high LDH (OR 1.17 for every 100 U/L increase; 95% CI, 1.02 to 1.34). None of the 12 paediatric patients had an adverse event. Conclusion: Advanced age, neutrophilia and high LDH predict poor outcomes in patients with SARS.

Inhibition of cytokine gene expression and induction of chemokine genes in non-lymphatic cells infected with SARS coronavirus

Background

SARS coronavirus (SARS-CoV) is the etiologic agent of the severe acute respiratory syndrome. SARS-CoV mainly infects tissues of non-lymphatic origin, and the cytokine profile of those cells can determine the course of disease. Here, we investigated the cytokine response of two human non-lymphatic cell lines, Caco-2 and HEK 293, which are fully permissive for SARS-CoV.

Results

A comparison with established cytokine-inducing viruses revealed that SARS-CoV only weakly triggered a cytokine response. In particular, SARS-CoV did not activate significant transcription of the interferons IFN-α, IFN-β, IFN-λ1, IFN-λ2/3, as well as of the interferon-induced antiviral genes ISG56 and MxA, the chemokine RANTES and the interleukine IL-6. Interestingly, however, SARS-CoV strongly induced the chemokines IP-10 and IL-8 in the colon carcinoma cell line Caco-2, but not in the embryonic kidney cell line 293.

Conclusion

Our data indicate that SARS-CoV suppresses the antiviral cytokine system of non-immune cells to a large extent, thus buying time for dissemination in the host. However, synthesis of IP-10 and IL-8, which are established markers for acute-stage SARS, escapes the virus-induced silencing at least in some cell types. Therefore, the progressive infiltration of immune cells into the infected lungs observed in SARS patients could be due to the production of these chemokines by the infected tissue cells.

Lessons from severe acute respiratory syndrome (SARS): implications for infection control

Severe acute respiratory syndrome (SARS), the first global epidemic in the 21^st century, affected over 8500 people in approximately 30 countries 1, 2, 3, 4, 5, 6, 7. With a crude mortality of 9%, its cause was quickly identified as a novel coronavirus that jumped species from animals to man. The SARS coronavirus epidemic, which began in the Fall of 2002, was related to the exotic food industry in southern China, initially involving disproportionate numbers of animal handlers, chefs, and caterers. Subsequently, person-to-person transmission spawned the outbreak. What distinguished this illness clinically was the fact that approximately half of the victims were health care workers (8), infected while caring for recognized or unrecognized patients with SARS. There are many curiosities and uncertainties surrounding the epidemic of SARS with lessons that may be useful to the community of infectious diseases physicians, especially when looking ahead to the next epidemic. Herein we relate our perspectives on useful lessons derived from a review of the SARS epidemic.

Real-time PCR in clinical microbiology: applications for routine laboratory testing

Real-time PCR has revolutionized the way clinical microbiology laboratories diagnose many human microbial infections. This testing method combines PCR chemistry with fluorescent probe detection of amplified product in the same reaction vessel. In general, both PCR and amplified product detection are completed in an hour or less, which is considerably faster than conventional PCR detection methods. Real-time PCR assays provide sensitivity and specificity equivalent to that of conventional PCR combined with Southern blot analysis, and since amplification and detection steps are performed in the same closed vessel, the risk of releasing amplified nucleic acids into the environment is negligible. The combination of excellent sensitivity and specificity, low contamination risk, and speed has made real-time PCR technology an appealing alternative to culture- or immunoassay-based testing methods for diagnosing many infectious diseases. This review focuses on the application of real-time PCR in the clinical microbiology laboratory.

Amotosalen photochemical inactivation of severe acute respiratory syndrome coronavirus in human platelet concentrates

A novel human coronavirus causing severe acute respiratory syndrome (SARS) emerged in epidemic form in early 2003 in China and spread worldwide in a few months. Every newly emerging human pathogen is of concern for the safety of the blood supply during and after an epidemic crisis. For this purpose, we have evaluated the inactivation of SARS-coronavirus (CoV) in platelet concentrates using an approved pathogen inactivation device, the INTERCEPT Blood System. Apheresis platelet concentrates (APCs) were inoculated with approximately 10(6) pfu mL(-1) of either Urbani or HSR1 isolates of SARS-CoV. The inoculated units were mixed with 150 microm amotosalen and illuminated with 3 J cm(-2) UV-A light. The viral titres were determined by plaque formation in Vero E6 cells. Mixing SARS-CoV with APC in the absence of any treatment decreased viral infectivity by approximately 0.5-1 log10. Following photochemical treatment, SARS-CoV was consistently inactivated to the limit of detection in seven independent APC units. No infectious virus was detected after treatment when up to one-third of the APC unit was assayed, demonstrating a mean log10-reduction of >6.2. Potent inactivation of SARS-CoV therefore extends the capability of the INTERCEPT Blood System in inactivating a broad spectrum of human pathogens including recently emerging respiratory viruses.

Viral load quantitation of SARS-coronavirus RNA using a one-step real-time RT-PCR

Introduction

Severe acute respiratory syndrome (SARS) is an emerging infectious disease that first occurred in humans in the People's Republic of China in November 2002 and has subsequently spread worldwide. A novel virus belonging to the Coronaviridae family has been identified as the cause of this pulmonary disease. The severity of the disease combined with its rapid spread requires the development of fast and sensitive diagnostic assays.

Results

A real-time quantitative RT-PCR was designed in the nsp11 region of the replicase 1B domain of the SARS-coronavirus (SARS-CoV) genome. To evaluate this quantitative RT-PCR, cRNA standards were constructed by in vitro transcription of SARS-CoV Frankfurt 1 RNA using T7 RNA polymerase, followed by real-time RT-PCR. The assay allowed quantitation over a range of 10² to 10⁸ RNA copies per reaction.

Conclusions

Extrapolated to clinical samples, this novel assay has a detection range of 10⁴ to 10¹⁰ copies of viral genome equivalents per millilitre. In comparison to the current de facto cRNA Artus Biotech standard, the in-house cRNA standard gives a 100-fold higher absolute quantity, suggesting a possible underestimation of the viral load when using the Artus Biotech standard.

Immunofluorescence assay for detection of the nucleocapsid antigen of the severe acute respiratory syndrome (SARS)-associated coronavirus in cells derived from throat wash samples of patients with SARS

An antigen detection assay for severe acute respiratory syndrome (SARS) coronavirus was established in this study by an indirect immunofluorescence test, which utilized cells derived from throat wash samples of patients with SARS and a rabbit serum that recognized the nucleocapsid protein of SARS-associated coronavirus (SARS-CoV) but not that of other human coronavirus tested. It detected SARS-CoV in 11 of 17 (65%) samples from SARS patients as early as day 2 of illness but in none of the 10 samples from healthy controls. Compared with other diagnostic modalities for detecting SARS-CoV, this assay is simpler, more convenient, and economical. It could be an alternative for early and rapid diagnosis, should SARS return in the future.

Detection of severe acute respiratory syndrome coronavirus RNA in plasma during the course of infection

We examined severe acute respiratory syndrome-associated coronavirus (SARS-CoV) RNA in plasma of 32 patients (probable SARS cases) by a quantitative real-time reverse transcription-PCR assay and reported that the highest detection rate, 75%, was found between day 5 and day 7 of illness, followed by rates of 64, 50, and 38% found between day 8 and day 11, day 2 and day 4, and day 12 and day 16, respectively. Analysis of sequential SARS-CoV load in plasma from six cases revealed different patterns of viremia, with the peak between day 4 and day 8. Our findings of the high detection rate of SARS-CoV RNA in plasma before day 11, together with the relative convenience of collecting and handling plasma, suggest that plasma can be used for early diagnosis of SARS.

Nitric oxide inhibits the replication cycle of severe acute respiratory syndrome coronavirus

Nitric oxide (NO) is an important signaling molecule between cells which has been shown to have an inhibitory effect on some virus infections. The purpose of this study was to examine whether NO inhibits the replication cycle of the severe acute respiratory syndrome coronavirus (SARS CoV) in vitro. We found that an organic NO donor, S-nitroso-N-acetylpenicillamine, significantly inhibited the replication cycle of SARS CoV in a concentration-dependent manner. We also show here that NO inhibits viral protein and RNA synthesis. Furthermore, we demonstrate that NO generated by inducible nitric oxide synthase, an enzyme that produces NO, inhibits the SARS CoV replication cycle.

SARS transmission pattern in Singapore reassessed by viral sequence variation analysis

BACKGROUND

Epidemiological investigations of infectious disease are mainly dependent on indirect contact information and only occasionally assisted by characterization of pathogen sequence variation from clinical isolates. Direct sequence analysis of the pathogen, particularly at a population level, is generally thought to be too cumbersome, technically difficult, and expensive. We present here a novel application of mass spectrometry (MS)-based technology in characterizing viral sequence variations that overcomes these problems, and we apply it retrospectively to the severe acute respiratory syndrome (SARS) outbreak in Singapore.

METHODS AND FINDINGS

The success rate of the MS-based analysis for detecting SARS coronavirus (SARS-CoV) sequence variations was determined to be 95% with 75 copies of viral RNA per reaction, which is sufficient to directly analyze both clinical and cultured samples. Analysis of 13 SARS-CoV isolates from the different stages of the Singapore outbreak identified nine sequence variations that could define the molecular relationship between them and pointed to a new, previously unidentified, primary route of introduction of SARS-CoV into the Singapore population. Our direct determination of viral sequence variation from a clinical sample also clarified an unresolved epidemiological link regarding the acquisition of SARS in a German patient. We were also able to detect heterogeneous viral sequences in primary lung tissues, suggesting a possible coevolution of quasispecies of virus within a single host.

CONCLUSION

This study has further demonstrated the importance of improving clinical and epidemiological studies of pathogen transmission through the use of genetic analysis and has revealed the MS-based analysis to be a sensitive and accurate method for characterizing SARS-CoV genetic variations in clinical samples. We suggest that this approach should be used routinely during outbreaks of a wide variety of agents, in order to allow the most effective control.

Virus-specific RNA and antibody from convalescent-phase SARS patients discharged from hospital

The prevalence of SARS-CoV in bodily excretions was determined.

Severe acute respiratory syndrome (SARS) is caused by a novel coronavirus (SARS-CoV). In a longitudinal cross-sectional study, we determined the prevalence of virus in bodily excretions and time of seroconversion in discharged patients with SARS. Conjunctival, throat, stool, and urine specimens were collected weekly from 64 patients and tested for SARS-CoV RNA by real-time polymerase chain reaction; serum samples were collected weekly and tested for SARS-CoV antibody with indirect enzyme immunoassay and immunofluorescence assay. In total, 126 conjunctival, 124 throat swab, 116 stool, and 124 urine specimens were analyzed. Five patients had positive stool samples, collected in weeks 5–9. Two patients seroconverted in weeks 7 and 8; the others were seropositive at the first serum sample collection. In this study, 5 (7.8%) of 64 patients continued to shed viral RNA in stool samples only, for up to week 8 of illness. Most seroconversions occurred by week 6 of illness.

Emerging infections in transfusion medicine

The risk of transfusion-transmitted infectious diseases (TTIDs) has declined dramatically in high-income nations over the past 2 decades, primarily because of extraordinary success in preventing HIV and other established transfusion-transmitted viruses from entering the blood supply. Despite this achievement, TTIDs remain a public health concern, and attention is refocusing on new and emerging pathogens, such as West Nile virus, infectious proteins (the presumed cause of variant Creutzfeldt-Jakob disease), and other transmissible organisms such as bacteria and parasites. In this article the authors concentrate on this heterogeneous group of infectious agents, describe individual pathogens and the risks they pose to transfusion recipients, and comment on existing and evolving procedures that are designed to protect the blood supply from this threat.

Real-time Fluorescent PCR Techniques to Study Microbial-Host Interactions

This chapter describes how real-time polymerase chain reaction (PCR) performs and how it may be used to detect microbial pathogens and the relationship they form with their host. Research and diagnostic microbiology laboratories contain a mix of traditional and leading-edge, in-house and commercial assays for the detection of microbes and the effects they impart upon target tissues, organs, and systems. The PCR has undergone significant change over the last decade, to the extent that only a small proportion of scientists have been able or willing to keep abreast of the latest offerings. The chapter reviews these changes. It discusses the second-generation of PCR technology-kinetic or real-time PCR, a tool gaining widespread acceptance in many scientific disciplines but especially in the microbiology laboratory.

The aetiology, origins, and diagnosis of severe acute respiratory syndrome

Severe acute respiratory syndrome (SARS) is a new infectious disease that first emerged in Guangdong province, China, in November, 2002. A novel coronavirus was later identified in patients with SARS. The detection of the virus in these patients, its absence in healthy controls or other patients with atypical pneumonia, and the reproduction of a similar disease in a relevant animal model fulfilled Koch's postulates for implicating this coronavirus as the causal agent of SARS. The full genome sequence was determined within weeks of the virus's identification. The rapid progress in the aetiology, the development of laboratory diagnostic tests, and the defining of routes of viral transmission were facilitated through a unique WHO-coordinated virtual network of laboratories, which shared information on a real-time basis through daily teleconferences. Subsequent studies have indicated that the SARS coronavirus is of animal origin, that its precursor is still present in animal populations within the region, and that live-animal markets in southern China may have provided the animal-human interphase that allowed this precursor virus to adapt to human-human transmission. These findings underscore the potential for the re-emergence of SARS and the need for laboratory tests for early diagnosis. However, the low viral load in the respiratory tract makes early diagnosis of SARS a diagnostic challenge, although improvements in the sensitivity of molecular diagnostic methods continue to be made.

Emerging viral infections

"Emerging infections" have been defined as infections that have newly appeared, that have appeared previously but are expanding in incidence and geographic range, or that threaten to increase in the near future. This article focuses on nine emerging viral infectious agents. These viruses illustrate how such agents emerge: by encroaching on previously unvisited habitats (eg, hantaviruses), by air travel (eg, SARS), and by accidental importation (eg, monkeypox). Additionally, the example of SARS demonstrates not only how quickly emerging viral infections can spread but also how quickly they can be identified and contained with motivated cooperation.

Severe acute respiratory syndrome (SARS) in intensive care units (ICUs): limiting the risk to healthcare workers

The global epidemic of severe acute respiratory syndrome (SARS) during the first half of 2003 resulted in over 8000 cases with more than 800 deaths. Many of those who eventually died, did so in the critical (intensive) care units of various hospitals around the world, and many secondary cases of SARS arose in healthcare workers looking after such patients in these units. Research on SARS coronavirus (SARS CoV) demonstrated that this virus belongs to the same family of viruses, the Coronaviridae that causes the common cold, with some important differences. Properties of this virus have been discovered which can be used to develop important infection control policies within hospitals to limit the number of secondary cases. These properties include environmental survival, transmissibility, viral load in various organs and fluids and periods of symptomatic illness during which infectivity is greatest. Various barrier methods were used throughout the epidemic to protect healthcare workers from SARS, with varying degrees of success. Treatment of SARS patients has mainly involved steroid therapy, with or without ribavirin, but there is no consensus on the best treatment protocol, as yet. This review focuses on the implications of SARS for healthcare workers and patients on critical care units.