[Factors of the hemostasis system as biomarkers of severe course of acute viral infections]. / Faktory sistemy gemostaza kak biomarkery tyazhelogo techeniya ostrykh virusnykh infektsii.

The authors give literature review of hemostasis and immune system factors intraction as main biomarkers of a severe cause of viral infectious diseases. Pro-inflamatory cytokines as the main markers of inflammation, can serve both as biomarkers of the clinical severity of the infectious process and reflect the state of the hemostatic and fibrinolytic systems, since components of these systems are present in various structures of the central nervous system and affect the development of neurons and synaptic plasticity. An inverse correlation has been proven between the concentration of D-dimer and the oxygenation index, and the development of DIC is not associated with the presence of respiratory failure in patients with influenza type A, while the ferritin concentration directly reflects the severity of the disease. One of the markers of endothelial damage may be soluble thrombomodulin, which, however, is rarely used in routine clinical practice. Cytoflavin is a highly effective pathogenetic drug that affects various parts of the hemostasis system, has anti-ischemic, antioxidant, antihypoxic, immunocorrective effect, which is indicated for any generalized infectious disease since its debut.

The development of droplet-based microfluidic virus detection technology for human infectious diseases.

Virus-based human infectious diseases have a significant negative impact on people's health and social development. The need for quick, accurate, and early viral infection detection in preventive medicine is expanding. A microfluidic control is particularly suitable for point-of-care-testing virus diagnosis due to its advantages of low sample consumption, quick detection speed, simple operation, multi-functional integration, small size, and easy portability. It is also thought to have significant development potential and a wide range of application prospects in the research on virus detection technology. In an effort to aid researchers in creating novel microfluidic tools for virus detection, this review highlights recent developments of droplet-based microfluidics in virus detection research and also discusses the challenges and opportunities for rapid virus detection.

Nucleic acid hybridization-based detection of pathogenic RNA using microscale thermophoresis.

Infectious diseases are one of the world's leading causes of morbidity. Their rapid spread emphasizes the need for accurate and fast diagnostic methods for large-scale screening. Here, we describe a robust method for the detection of pathogens based on microscale thermophoresis (MST). The method involves the hybridization of a fluorescently labeled DNA probe to a target RNA and the assessment of thermophoretic migration of the resulting complex in solution within a 2 to 30-time window. We found that the thermophoretic migration of the nucleic acid-based probes is primarily determined by the fluorescent molecule used, rather than the nucleic acid sequence of the probe. Furthermore, a panel of uniformly labeled probes that bind to the same target RNA yields a more responsive detection pattern than a single probe, and moreover, can be used for the detection of specific pathogen variants. In addition, intercalating agents (ICA) can be used to alter migration directionality to improve detection sensitivity and resolving power by several orders of magnitude. We show that this approach can rapidly diagnose viral SARS-CoV2, influenza H1N1, artificial pathogen targets, and bacterial infections. Furthermore, it can be used for anti-microbial resistance testing within 2 h, demonstrating its diagnostic potential for early pathogen detection.

Cycle threshold dynamics of non-severe acute respiratory coronavirus virus 2 (SARS-CoV-2) respiratory viruses.

OBJECTIVE: Many providers use severe acute respiratory coronavirus virus 2 (SARS-CoV-2) cycle thresholds (Ct values) as approximate measures of viral burden in association with other clinical data to inform decisions about treatment and isolation. We characterized temporal changes in Ct values for non-SARS-CoV-2 respiratory viruses as a first step to determine whether cycle thresholds could play a similar role in the management of non-SARS-CoV-2 respiratory viruses. DESIGN: Retrospective cohort study. SETTING: Brigham and Women's Hospital, Boston. METHODS: We retrospectively identified all adult patients with positive nasopharyngeal PCRs for influenza, respiratory syncytial virus (RSV), parainfluenza, human metapneumovirus (HMPV), rhinovirus, or adenovirus between January 2022 and March 2023. We plotted Ct distributions relative to days since symptom onset, and we assessed whether distributions varied by immunosuppression and other comorbidities. RESULTS: We analyzed 1,863 positive samples: 506 influenza, 502 rhinovirus, 430 RSV, 219 HMPV, 180 parainfluenza, 26 adenovirus. Ct values were generally 25-30 on the day of symptom onset, lower over the ensuing 1-3 days, and progressively higher thereafter with Ct values ≥30 after 1 week for most viruses. Ct values were generally higher and more stable over time for rhinovirus. There was no association between immunocompromised status and median intervals from symptom onset until Ct values were ≥30. CONCLUSIONS: Ct values relative to symptom onset for influenza, RSV, and other non-SARS-CoV-2 respiratory viruses generally mirror patterns seen with SARS-CoV-2. Further data on associations between Ct values and viral viability, transmissibility, host characteristics, and response to treatment for non-SARS-CoV-2 respiratory viruses are needed to determine how clinicians and infection preventionists might integrate Ct values into treatment and isolation decisions.

Point-of-care neutrophil and monocyte surface markers differentiate bacterial from viral infections at the emergency department within 30†min.

Rapid discrimination between viral and bacterial infections in a point-of-care setting will improve clinical outcome. Expression of CD64 on neutrophils (neuCD64) increases during bacterial infections, whereas expression of CD169 on classical monocytes (cmCD169) increases during viral infections. The diagnostic value of automated point-of-care neuCD64 and cmCD169 analysis was assessed for detecting bacterial and viral infections at the emergency department. Additionally, their value as input for machine learning models was studied. A prospective observational cohort study in patients suspected of infection was performed at an emergency department. A fully automated point-of-care flow cytometer measured neuCD64, cmCD169, and additional leukocyte surface markers. Flow cytometry data were gated using the FlowSOM algorithm. Bacterial and viral infections were assessed in standardized clinical care. The sole and combined diagnostic value of the markers was investigated. Clustering based on unsupervised machine learning identified unique patient clusters. Eighty-six patients were included. Thirty-five had a bacterial infection, 30 had a viral infection, and 21 had no infection. neuCD64 was increased in bacterial infections (P < 0.001), with an area under the receiver operating characteristic curve (AUROC) of 0.73. cmCD169 was higher in virally infected patients (P < 0.001; AUROC 0.79). Multivariate analyses incorporating additional markers increased the AUROC for bacterial and viral infections to 0.86 and 0.93, respectively. The additional clustering identified 4 distinctive patient clusters based on infection type and outcome. Automated neuCD64 and cmCD169 determination can discriminate between bacterial and viral infections. These markers can be determined within 30 min, allowing fast infection diagnostics in the acute clinical setting.

Healthcare-associated respiratory viral infections after discontinuing universal masking.

In November 2022, our pediatric hospital replaced the requirement for universal masking of all healthcare personnel and visitors in all clinical buildings with a requirement for masking only during patient encounters. Following this change, we observed an immediate, substantial, and sustained increase in healthcare-associated respiratory viral infections.

Evidence of the simultaneous replications of active viruses in specimens positive for multiple respiratory viruses.

IMPORTANCE: Since the pandemic of coronavirus diseases 2019, the use of real-time PCR assay has become widespread among people who were not familiar with it in virus detection. As a result, whether a high real-time PCR value in one time test indicates virus transmissibly became a complicated social problem, regardless of the difference in assays and/or amplification conditions, the time and number of diagnostic test during the time course of infection. In addition, the multiple positives in the test of respiratory viruses further add to the confusion in the interpretation of the infection. To address this issue, we performed virus isolation using pediatric SARI (severe acute respiratory infections) specimens on air-liquid interface culture of human bronchial/tracheal epithelial cell culture. The result of this study can be a strong evidence that the specimens showing positivity for multiple agents in real-time PCR tests possibly contain infectious viruses.

Validation of the VirCapSeq-VERT system for differential diagnosis, detection, and surveillance of viral infections.

IMPORTANCE: Broad range assay for accurate and sensitive diagnostics.

Metagenomic next-generation sequencing of cell-free DNA for the identification of viruses causing central nervous system infections.

IMPORTANCE: This study provides significant new data on the application of metagenomic next-generation sequencing (mNGS) to clinical diagnostics of central nervous system (CNS) viral infections, which can have high mortality rates and severe sequelae. Conventional diagnostic procedures for identifying viruses can be inefficient and rely on preconceived assumptions about the pathogen, making mNGS an appealing alternative. However, the effectiveness of mNGS is affected by the presence of human DNA contamination, which can be minimized by using cell-free DNA (cfDNA) instead of whole-cell DNA (wcDNA). This multi-center retrospective study of patients with suspected viral CNS infection found that mNGS using cfDNA had a significantly lower proportion of human DNA and higher sensitivity for detecting viruses than mNGS using wcDNA. Herpesviruses, particularly VZV, were found to be the most common DNA viruses in these patients. Overall, mNGS using cfDNA is a promising complementary diagnostic method for detecting CNS viral infections.

Host-response transcriptional biomarkers accurately discriminate bacterial and viral infections of global relevance.

Diagnostic limitations challenge management of clinically indistinguishable acute infectious illness globally. Gene expression classification models show great promise distinguishing causes of fever. We generated transcriptional data for a 294-participant (USA, Sri Lanka) discovery cohort with adjudicated viral or bacterial infections of diverse etiology or non-infectious disease mimics. We then derived and cross-validated gene expression classifiers including: 1) a single model to distinguish bacterial vs. viral (Global Fever-Bacterial/Viral [GF-B/V]) and 2) a two-model system to discriminate bacterial and viral in the context of noninfection (Global Fever-Bacterial/Viral/Non-infectious [GF-B/V/N]). We then translated to a multiplex RT-PCR assay and independent validation involved 101 participants (USA, Sri Lanka, Australia, Cambodia, Tanzania). The GF-B/V model discriminated bacterial from viral infection in the discovery cohort an area under the receiver operator curve (AUROC) of 0.93. Validation in an independent cohort demonstrated the GF-B/V model had an AUROC of 0.84 (95% CI 0.76-0.90) with overall accuracy of 81.6% (95% CI 72.7-88.5). Performance did not vary with age, demographics, or site. Host transcriptional response diagnostics distinguish bacterial and viral illness across global sites with diverse endemic pathogens.

Rapid antigen test for adenovirus in children: Age and onset of symptoms are important / Antígeno de adenovirus en niños: la edad y la aparición de los síntomas son importantes

Introduction: Respiratory infection is the most common human adenovirus (HAdV) disease accounting for 7–8% of viral respiratory diseases in children less than 5 years. Differentiation of bacterial infections and viral infections is a common clinical problem. Material and methods: One hundred oropharyngeal swabs obtained from October 2019 to November 2020 from patients attending the paediatric emergency room with suspicion of upper respiratory tract infection and negative results in influenza and RSV tests were included. Oropharyngeal swabs specimens were rapidly processed with STANDARD™ F Adeno Respi Ag FIA and the results were confirmed by RealStar® Adenovirus PCR Kit 1.0 (Altona diagnostics). Results: STANDARD™ F Adeno Respi Ag FIA had sensitivity and specificity values of 71.93% and 100% respectively. The performance of the test was higher in samples from children younger than 24 months and taken less than 72h since the beginning of symptoms. In this subgroup the test had 88.8% sensitivity and 100% specificity. Conclusion: STANDARD™ F Adeno Respi Ag FIA may improve the management of respiratory diseases in children younger than 24 months and less than 72h since the beginning of symptoms in paediatric emergency rooms.(AU)

Introducción: Las infecciones respiratorias son la enfermedad más común asociada a los adenovirus humanos (AdvH)y causan del 7 al 8% de las enfermedades respiratorias víricas en niños menores de 5 años. La distinción entre las infecciones bacterianas y las víricas constituye un problema clínico frecuente. Materiales y métodos: El estudio incluyó 100 hisopos orofaríngeos obtenidos entre octubre de 2019 y noviembre de 2020 de pacientes que habían acudido a los servicios de urgencias pediátricas con sospecha de infección de las vías respiratorias superiores y resultados negativos en las pruebas de gripe y VRS. Las muestras de los hisopos orofaríngeos se procesaron rápidamente con Standard™ F Adeno Respi Ag FIA y los resultados se confirmaron mediante RealStar® Adenovirus PCR Kit 1.0 (altona Diagnostics). Resultados: Standard™ F Adeno Respi Ag FIA tenía unos valores de sensibilidad y especificidad del 71,93% y el 100%, respectivamente. El rendimiento de la prueba fue superior en muestras de niños menores de 24 meses y tomadas menos de 72 horas después del inicio de los síntomas. En este subgrupo, la prueba tuvo una sensibilidad del 88,8% y una especificidad del 100%. Conclusión: Standard™ F Adeno Respi Ag FIA puede mejorar la gestión de las enfermedades respiratorias en niños menores de 24 meses con menos de 72 desde el inicio de los síntomas en servicios de urgencias pediátricas.(AU)

Shotgun metagenomics to investigate unknown viral etiologies of pediatric meningoencephalitis.

INTRODUCTION: Meningoencephalitis in children poses a diagnostic challenge, as etiology remains unknown for most of patients. Viral metagenomics by shotgun sequencing represents a powerful tool for investigating unknown viral infections related to these cases. PATIENTS AND METHODS: In a two-year, reference-centre, retrospective study, we investigated the usefulness of viral metagenomics of cerebrospinal fluid (CSF) for the diagnosis of viral infectious meningoencephalitis in forty seven pediatric patients, forty of them previously tested negative with a routine neurologic panel of viral targets that included herpesvirus 1-3 and enterovirus. We enhanced the detection by targeting viral sequences by hybrid capture. Raw sequence data was analysed using three bioinformatics pipelines. RESULTS: Out of forty remaining children with meningoencephalitis of unknown viral etiology, a significant detection of viral nucleic acid by shotgun sequencing was found in twenty one, which was confirmed in ten of them by specific PCR: seven human endogenous retrovirus K113 (HER K113), one parechovirus 3, one human herpesvirus 5 (HHV5); one enterovirus B (Echovirus 9). The remaining eleven CSF were not confirmed by PCR: three rotavirus, one human herpesvirus 7 (HHV7), one influenza A, one mastadenovirus C, one sindbis virus, one torque teno virus, one human immunodeficiency virus 1 (HIV-1), one human alphaherpesvirus 3 (HHV3), one human alphaherpesvirus 2 (HHV2). CONCLUSIONS: Underutilization of currently available meningitis-encephalitis diagnostic techniques such as BioFire® FilmArray® is the main cause of undiagnosed cases of meningoencephalitis. However, in this study we detected uncommon viruses that should be considered, including virus, rotavirus, sindbis virus, influenza A virus and HHV7. No other viral sequences that could be readily linked to CNS inflammation were detected. Some findings may stem from reagent or sample contamination, as seen with papillomavirus; for others, the clinical relevance of the virus remains uncertain and should be substantiated by further studies, as is the case with endogenous retrovirus K113 virus. Online bioinformatics pipeline CZID represents a valuable tool for analysing shotgun sequencing data in cases of neurological conditions with unknown etiology. Altogether, this study highlights the potential of shotgun sequencing in identifying previously unknown viral neuropathogens and sheds light on the interpretation issues related to its application in clinical microbiology.

Systemic corticosteroids for outpatient respiratory viral infections in lung transplant recipients.

INTRODUCTION: Respiratory viral infections (RVI) in lung transplant recipients (LTR) have variably been associated with rejection and chronic lung allograft dysfunction. Our center has used systemic corticosteroids to treat outpatient RVI in some cases, but evidence is limited. We reviewed all adult LTR diagnosed with outpatient RVI January 2017 to December 2019. The primary outcome was recovery of lung function (forced expiratory volume in 1 s [FEV1]) at next stable visit between 1 and 12 months postinfection, expressed as a ratio over stable preinfection FEV1 (FEV1 recovery ratio). METHODS: We identified 100 adult LTR with outpatient RVI diagnoses eligible for study, 36% of whom received corticosteroids. We modelled the adjusted association between corticosteroid use and FEV1 recovery ratio using linear regression. RESULTS: Steroid-treated patients had a lower FEV1 presentation ratio (0.92 vs. 1.04, p = .0070) and were more likely to have chronic lung allograft dysfunction at time of infection (25% vs. 5%, p = .0077). Mean FEV1 recovery ratio was 1.02 (SD 0.19) with no association with corticosteroid therapy via multivariable linear regression (p = .5888). CONCLUSIONS: Steroid treatment was not associated with FEV1 recovery. This suggests corticosteroids may not have a role in the management of RVI in this population.

A multi-platform approach to identify a blood-based host protein signature for distinguishing between bacterial and viral infections in febrile children (PERFORM): a multi-cohort machine learning study.

BACKGROUND: Differentiating between self-resolving viral infections and bacterial infections in children who are febrile is a common challenge, causing difficulties in identifying which individuals require antibiotics. Studying the host response to infection can provide useful insights and can lead to the identification of biomarkers of infection with diagnostic potential. This study aimed to identify host protein biomarkers for future development into an accurate, rapid point-of-care test that can distinguish between bacterial and viral infections, by recruiting children presenting to health-care settings with fever or a history of fever in the previous 72 h. METHODS: In this multi-cohort machine learning study, patient data were taken from EUCLIDS, the Swiss Pediatric Sepsis study, the GENDRES study, and the PERFORM study, which were all based in Europe. We generated three high-dimensional proteomic datasets (SomaScan and two via liquid chromatography tandem mass spectrometry, referred to as MS-A and MS-B) using targeted and untargeted platforms (SomaScan and liquid chromatography mass spectrometry). Protein biomarkers were then shortlisted using differential abundance analysis, feature selection using forward selection-partial least squares (FS-PLS; 100 iterations), along with a literature search. Identified proteins were tested with Luminex and ELISA and iterative FS-PLS was done again (25 iterations) on the Luminex results alone, and the Luminex and ELISA results together. A sparse protein signature for distinguishing between bacterial and viral infections was identified from the selected proteins. The performance of this signature was finally tested using Luminex assays and by calculating disease risk scores. FINDINGS: 376 children provided serum or plasma samples for use in the discovery of protein biomarkers. 79 serum samples were collected for the generation of the SomaScan dataset, 147 plasma samples for the MS-A dataset, and 150 plasma samples for the MS-B dataset. Differential abundance analysis, and the first round of feature selection using FS-PLS identified 35 protein biomarker candidates, of which 13 had commercial ELISA or Luminex tests available. 16 proteins with ELISA or Luminex tests available were identified by literature review. Further evaluation via Luminex and ELISA and the second round of feature selection using FS-PLS revealed a six-protein signature: three of the included proteins are elevated in bacterial infections (SELE, NGAL, and IFN-γ), and three are elevated in viral infections (IL18, NCAM1, and LG3BP). Performance testing of the signature using Luminex assays revealed area under the receiver operating characteristic curve values between 89·4% and 93·6%. INTERPRETATION: This study has led to the identification of a protein signature that could be ultimately developed into a blood-based point-of-care diagnostic test for rapidly diagnosing bacterial and viral infections in febrile children. Such a test has the potential to greatly improve care of children who are febrile, ensuring that the correct individuals receive antibiotics. FUNDING: European Union's Horizon 2020 research and innovation programme, the European Union's Seventh Framework Programme (EUCLIDS), Imperial Biomedical Research Centre of the National Institute for Health Research, the Wellcome Trust and Medical Research Foundation, Instituto de Salud Carlos III, Consorcio Centro de Investigación Biomédica en Red de Enfermedades Respiratorias, Grupos de Refeencia Competitiva, Swiss State Secretariat for Education, Research and Innovation.

[Viral Respiratory Tract Infection Agents Detected Between Years 2019-2021, COVID-19, and Co-Infections]. / 2019-2021 Yillari Arasinda Saptanan Viral Solunum Yolu Enfeksiyonu Etkenleri, COVID-19 ve Ko-Enfeksiyonlar.

Respiratory tract infections are a major cause of morbidity and mortality at all ages and are seen as a very important public health problem all over the world. In this study, we aimed to evaluate the effect of the pandemic on the epidemiological and seasonal characteristics of the agents by analyzing the respiratory viral infection agents, viral co-infections and associations with Coronavirus diseases-2019 (COVID-19) studied by multiplex polymerase chain reaction (PCR) test in the molecular microbiology laboratory in a three-year period, including the one-year period before the pandemic. Between March 2019 and December 2021, 8825 respiratory tract specimens accepted to the molecular microbiology laboratory with respiratory tract multiplex PCR test requests were included in the study. In addition, severe acute respiratory syndrome (SARS-CoV-2) PCR test results of the patients with positive results with respiratory tract multiplex PCR test, which were studied within ± 3 days, were evaluated retrospectively. Respiratory viral pathogens were detected using FTD Respiratory Pathogens 21 kit (Fast Tract Diagnostics, Siemens Healthineers Company). Two different kits based on real-time reverse transcription PCR were used for SARS-CoV-2 RNA detection in different periods. According to our results, at least one viral agent was detected in 2156 (24.4%) of a total of 8825 samples and a single agent was detected in 1843 (85.5%) of these. The distribution of viruses in the samples with a single agent was determined as RV, RSV A/B, HCoVs, AdV, flu A virus, MPV A/B, PIV 1-4, flu B virus, EV, BoV and PeV, in order of frequency. Multiple agents were found in 313 (14.5%) of these 2156 samples. They were found to be two agents in 291 samples, three in 21 samples and four in one sample. When the SARS-CoV-2 PCR test results of the patients who had positive results with respiratory tract multiplex PCR and who were studied within ± 3 days were evaluated retrospectively, SARS-CoV-2 RNA was detected in 45 (3.5%) of 1277 samples in which at least one agent was detected. In four of these patients, SARS-CoV-2 was found together with multiple agents. Consequently, there was a sharp decrease in the prevalence of all viral agents during the pandemic period. It was evaluated that besides the COVID-19 infection, the restrictions applied during the pandemic period were also effective in this situation.

Regulatory circular RNAs in viral diseases: applications in diagnosis and therapy.

Circular RNA (circRNA) forms closed loops via back-splicing in precursor mRNA, resisting exonuclease degradation. In higher eukaryotes, protein-coding genes create circRNAs through exon back-splicing. Unlike mRNAs, circRNAs possess unique production and structural traits, bestowing distinct cellular functions and biomedical potential. In this review, we explore the pivotal roles of viral circRNAs and associated RNA in various biological processes. Analysing the interactions between viral circRNA and host cellular machinery yields fresh insights into antiviral immunity, catalysing the development of potential therapeutics. Furthermore, circRNAs serve as enduring biomarkers in viral diseases due to their stable translation within specific tissues. Additionally, a deeper understanding of translational circRNA could expedite the establishment of circRNA-based expression platforms, meeting the rising demand for broad-spectrum viral vaccines. We also highlight the applications of circular RNA in biomarker studies as well as circRNA-based therapeutics. Prospectively, we expect a technological revolution in combating viral infections using circRNA.

Effect of Viral Illness on Procalcitonin as a Predictor of Bacterial Infection in Febrile Infants.

OBJECTIVE: The impact of confirmed viral infections (CVI) on procalcitonin (PCT) levels in febrile infants aged 8-60 days with a bacterial illness (BI) is unknown. The objectives of the study were to (1) examine the association of CVI with PCT levels in patients with/without a concurrent BI, defined as bacteremia, meningitis, or urinary tract infection, and (2) assess PCT as a predictor of BI in infants with a concurrent CVI. METHODS: In this single-center, retrospective cohort study, we examined febrile infants aged 8-60 days presenting between January 1, 2018 and December 31, 2020. PCT levels were compared between groups, according to results of bacterial cultures and viral tests, using the Wilcoxon rank test. The prediction ability of PCT to detect BI with/without concurrent CVI was assessed by using area under the curve from logistic regression. RESULTS: Patients included: 404 BI-/CVI+, 73 BI+/CVI-, 48 BI+/CVI+, and 138 BI-/CVI-. Median PCT level in the BI+/CVI+ group was significantly lower when compared to BI+/CVI- (0.36 ng/mL vs 0.89 ng/mL), but significantly higher than the BI-/CVI- group (0.36 ng/mL vs 0.1 ng/mL). The presence of a CVI reduced the sensitivity of PCT in BI detection (68% vs 44%), with minimal impact specificity (93% vs 96%). CONCLUSIONS: In previously healthy febrile infants 8-60 days old, the presence of a CVI reduces the sensitivity of PCT BI detection without impacting its specificity. The impact of a CVI on PCT levels in febrile infants has implications for how this marker of infection should be considered when assessing risk of BI in infants.

Application of aptamer-based viral detection in animals.

Viral infections are common causes of diseases in animals and appropriate methods are increasingly being required to detect viral pathogens in animals. In this regard, similar to antigen- -antibody interactions, aptamers have high affinity and specificity for their respective target molecules, and can be selected using the Systematic Evolution of Ligands by EXponential enrichment (SELEX) technique. Recently, significant progress has been made in the development of aptamer selection and aptamer-based sensors for viral detection, and here we review some of the recent advances in aptamer-based detection of viral infections in animals. This review will serve as a comprehensive resource for aptamer-based strategies in viral diagnostics.