Screening the blood supply for West Nile virus RNA by nucleic acid amplification testing

In vitro enhancement of Zika virus infection by preexisting West Nile virus antibodies in human plasma-derived immunoglobulins revealed after P2 binding site-specific enrichment

Human immunoglobulin preparations contain a diverse range of polyclonal antibodies that reflect past immune responses against pathogens encountered by the blood donor population. In this study, we examined a panel of intravenous immunoglobulins (IGIVs) manufactured over the past two decades (1998-2020) for their capacity to neutralize or enhance Zika virus (ZIKV) infection in vitro. These IGIVs were selected specifically based on their production dates in relation to the occurrences of two flavivirus outbreaks in the U.S.: the West Nile virus (WNV) outbreak in 1999 and the ZIKV outbreak in 2015. As demonstrated by enzyme-linked immunosorbent assay (ELISA) experiments, IGIVs made before the ZIKV outbreak already harbored antibodies that bind to various peptides across the envelope protein of ZIKV because of the WNV outbreak. Using phage display, the most dominant binding site was mapped precisely to the P2 peptide between residues 211 and 230 within domain II, where BF1176-56, an anti-ZIKV monoclonal antibody, also binds. When tested in permissive Vero E6 cells for ZIKV neutralization, the IGIVs, even after undergoing rigorous enrichment for P2 binding specificity, failed, as did BF1176-56. Meanwhile, BF1176-56 enhanced ZIKV infection in both FcγRII-expressing K562 cells and human peripheral blood mononuclear cells. However, for enhancement by the IGIVs to be detected in these cells, a substantial increase in their P2 binding specificity was required, thus linking the P2 site with ZIKV enhancement in vitro. Our findings warrant further study of the significance of elevated levels of anti-WNV antibodies in IGIVs, considering that various mechanisms operating in vivo may modulate ZIKV infection outcomes.IMPORTANCEWe investigated the capacity of intravenous immunoglobulins manufactured previously over two decades (1998-2020) to neutralize or enhance Zika virus infection in vitro. West Nile virus antibodies in IGIVs could not neutralize Zika virus initially; however, once the IGIVs were concentrated further, they enhanced its infection. These findings lay the groundwork for exploring how preexisting WNV antibodies in IGIVs could impact Zika infection, both in vitro and in vivo. Our observations are historically significant, since we tested a panel of IGIV lots that were carefully selected based on their production dates which covered two major flavivirus outbreaks in the U.S.: the WNV outbreak in 1999 and the ZIKV outbreak in 2015. These findings will facilitate our understanding of the interplay among closely related viral pathogens, particularly from a historical perspective regarding large blood donor populations. They should remain relevant for future outbreaks of emerging flaviviruses that may potentially affect vulnerable populations.

West Nile Virus Emergence in Germany 2019: Looking for Hidden Human West Nile Virus Infections

Background: Autochthonous human West Nile virus (WNV) infections were notified in the infectious disease surveillance system in Germany in 2018 for the first time and every year since then. Since clinically apparent infections are infrequent, we conducted two studies to investigate subclinical infections of this emerging disease in Germany in 2019 to detect infections not visible to surveillance based on symptomatic infections: limited-scope blood donor testing and a serosurvey among employees at two Berlin zoos with a history of demonstrated WNV infections in animals. Methods: For the zoo study, employees of the two zoos in Berlin were invited to participate in the study in late 2019. Blood samples were drawn and tested for the presence of antibodies (immunoglobulin M [IgM] and immunoglobulin G [IgG]) against WNV, and two other flaviviruses present in Germany: Usutu virus and Tick-borne encephalitis virus (TBEV). For the study in blood donors, four blood establishments with collection sites in regions with documented WNV-infected animals in 2018 and 2019 participated in the study. All donations in these regions were tested for WNV genome from July to November 2019. Results: In the enzyme-linked immunosorbent assay, none of the 70 tested zoo employees were WNV IgM-positive, 8 were WNV IgG-positive, additional 2 participants had equivocal results. All 10 were negative in the virus neutralization test (VNT) for WNV, but positive in the VNT for TBEV. None of the 4273 samples from blood donors tested in areas with WNV-infected animals was positive for WNV-RNA. Conclusion: Our results indicate that WNV circulation in Germany, though clearly documented in animals in 2019, apparently affected very few humans. Still areas with WNV-positive animals remain risk areas for human infection as well.

Estimating the prevalence of two or more diseases using outcomes from multiplex group testing

When screening a population for infectious diseases, pooling individual specimens (e.g., blood, swabs, urine, etc.) can provide enormous cost savings when compared to testing specimens individually. In the biostatistics literature, testing pools of specimens is commonly known as group testing or pooled testing. Although estimating a population-level prevalence with group testing data has received a large amount of attention, most of this work has focused on applications involving a single disease, such as human immunodeficiency virus. Modern methods of screening now involve testing pools and individuals for multiple diseases simultaneously through the use of multiplex assays. Hou et al. (2017, Biometrics, 73, 656-665) and Hou et al. (2020, Biostatistics, 21, 417-431) recently proposed group testing protocols for multiplex assays and derived relevant case identification characteristics, including the expected number of tests and those which quantify classification accuracy. In this article, we describe Bayesian methods to estimate population-level disease probabilities from implementing these protocols or any other multiplex group testing protocol which might be carried out in practice. Our estimation methods can be used with multiplex assays for two or more diseases while incorporating the possibility of test misclassification for each disease. We use chlamydia and gonorrhea testing data collected at the State Hygienic Laboratory at the University of Iowa to illustrate our work. We also provide an online R resource practitioners can use to implement the methods in this article.

Transfusion-transmitted arboviruses: Update and systematic review

BACKGROUND

The detection of the first cases of transfusion-transmitted West Nile virus in 2002 posed a new challenge for transfusion safety. Institutions like the World Health Organization have stated that blood transfusion centers need to know the epidemiology of the different emerging infectious agents and their impact on blood transfusion. The aim of the study is to review the published cases of arbovirus transmission through transfusion of blood or blood components and to analyze their main clinical and epidemiological characteristics.

MATERIAL AND METHODS

Systematic literature searches were conducted in MEDLINE, Embase and Scopus. Pairs of review authors selected a variety of scientific publications reporting cases of transfusion-transmitted arboviruses. Main clinical and epidemiological characteristics were reviewed of the cases described. The study protocol was registered in PROSPERO CRD42021270355.

RESULTS

A total of 74 cases of transfusion-transmitted infections were identified from 10 arboviruses: West Nile virus (n = 42), dengue virus (n = 18), Zika virus (n = 3), yellow fever vaccine virus (n = 3), tick-borne encephalitis virus (n = 2), Japanese encephalitis virus (n = 2), Powassan virus (n = 1), St. Louis encephalitis virus (n = 1), Ross River virus (n = 1) and Colorado tick fever virus (n = 1). The blood component most commonly involved was red blood cells (N = 35, 47.3%; 95% confidence interval [CI] 35.9% to 58.7%). In 54.1% (N = 40; 95% CI: 42.7%-65.47%) of the cases, the recipient was immunosuppressed. Transmission resulted in death in 18.9% (N = 14; 95% CI: 10.0%-27.8%) of the recipients. In addition, 18 additional arboviruses were identified with a potential threat to transfusion safety.

DISCUSSION

In the last 20 years, the number of published cases of transfusion-transmitted arboviruses increased notably, implicating new arboviruses. In addition, a significant number of arboviruses that may pose a threat to transfusion safety were detected. In the coming years, it is expected that transmission of arboviruses will continue to expand globally. It is therefore essential that all responsible agencies prepare for this potential threat to transfusion safety.

Transfusion-transmissible dengue infections

Dengue is an important global health problem and is endemic in many developing and developed countries. Transmission of dengue may occur in several ways and information on transfusion-transmitted dengue is limited. We conducted a literature search on transfusion-related dengue using the PubMed, Scopus, Embase and Google Scholar databases and have summarized the findings. A number of apparently healthy blood donors have been found to be infected with the dengue virus (DENV) and thus may transmit the virus onto recipients of this blood. It is not possible to identify and exclude such donors at the donor selection stage and thus reliable screening tests should be available in highly endemic areas to ensure a safe blood supply.

Array testing for multiplex assays

Group testing involves pooling individual specimens (e.g., blood, urine, swabs, etc.) and testing the pools for the presence of disease. When the proportion of diseased individuals is small, group testing can greatly reduce the number of tests needed to screen a population. Statistical research in group testing has traditionally focused on applications for a single disease. However, blood service organizations and large-scale disease surveillance programs are increasingly moving towards the use of multiplex assays, which measure multiple disease biomarkers at once. Tebbs and others (2013, Two-stage hierarchical group testing for multiple infections with application to the Infertility Prevention Project. Biometrics69, 1064-1073) and Hou and others (2017, Hierarchical group testing for multiple infections. Biometrics73, 656-665) were the first to examine hierarchical group testing case identification procedures for multiple diseases. In this article, we propose new non-hierarchical procedures which utilize two-dimensional arrays. We derive closed-form expressions for the expected number of tests per individual and classification accuracy probabilities and show that array testing can be more efficient than hierarchical procedures when screening individuals for multiple diseases at once. We illustrate the potential of using array testing in the detection of chlamydia and gonorrhea for a statewide screening program in Iowa. Finally, we describe an R/Shiny application that will help practitioners identify the best multiple-disease case identification algorithm.

Serological Diagnosis of Flavivirus-Associated Human Infections

Arthropod-borne viruses (arboviruses) belonging to the Flavivirus genus of the Flaviviridae family, are a major public health threat in tropical and subtropical regions, and have recently become a medical concern in temperate zones. Most flaviviruses are classified as zoonotic viruses. Human flavivirus infections can be asymptomatic, responsible for unspecific symptoms in the first few days following infection, or responsible for severe complications potentially resulting in death. During the first days following symptom onset, laboratory diagnosis of acute human flavivirus infection is mainly based on molecular detection of the viral genome by RT-PCR methods, followed by the capture of specific antibodies using serological tests after the first week of infection. The detection of antibodies that have virus neutralizing activity can be used to confirm flavivirus infection. However, human flavivirus infections induce the production of cross-reactive antibodies, often making serology inconclusive. Indeed, serological diagnosis of flavivirus infection can be hampered by a patient's history of flavivirus exposure, particularly in regions where multiple antigenically related flaviviruses co-circulate. We focus our mini review on conventional immunoassays that allow the diagnosis of major flavivirus-associated human infections in basic, routine and high-profile central health centers; and the interpretation of diagnostic serology tests for patients living within different epidemiological situations.

Blood Transfusion-Associated Infections in the Twenty-First Century: New Challenges

Blood transfusions are vital components of modern medical treatment to which there is no viable alternative despite efforts to create artificial blood. Each year thousands of lives are saved by blood transfusions in every country of the world. However, blood and blood products can result in significant adverse events including immunologic reactions, infections, inefficacy, and others which can sometimes result in death and severe disability. Thus, the sustainability of safe blood systems and costs are considered to be at crisis level. In industrialized countries, the risk of transfusion-transmitted infections such as HIV, syphilis, hepatitis viruses B and C are very low [generally [<1 in a million units], but in developing countries [especially in Africa] blood safety is still not assured. Compounding the problem of blood/product safety with respect to infectious agents are new emerging infectious microbes that are not being routinely tested for in blood that are donated. This chapter reviews the infectious risk of blood transfusions, types, mode and geographic variation, and the methods being used by blood services to attenuate and prevent these risks.

Zika Virus and Other Emerging Arboviral Central Nervous System Infections

PURPOSE OF REVIEW

In recent years, we have observed the emergence and reemergence of a number of arthropod-borne viruses (arboviruses). Zika virus is the most recent addition to this group, first causing sporadic cases of uncomplicated febrile illness followed by sizeable outbreaks in the Pacific. However, the epidemiology and clinical features of Zika virus infection have changed rapidly and dramatically; it is now recognized as causing Guillain-Barré syndrome (GBS) in children and adults and congenital abnormalities in infected fetuses. This article reviews the epidemiology, clinical features, and diagnosis of Zika virus-associated neurologic illness and briefly reviews features of West Nile virus and Japanese encephalitis virus.

RECENT FINDINGS

Zika virus has emerged as a significant human pathogen in recent years. In 2015, it began to cause large outbreaks of febrile rash illness in South America and the Caribbean. During these large Zika virus outbreaks, a significant increase in the incidence of GBS was also observed in multiple countries/territories. Zika virus-associated GBS has several unique features, including a relatively short interval between febrile illness and GBS onset, an unusually high incidence among older people, and prominent cranial nerve abnormalities. Congenital Zika syndrome includes a myriad of abnormalities, including microcephaly, lissencephaly, hydrocephalus, arthrogryposis, and parenchymal calcifications. Currently, no treatment has been identified for Zika virus, although work on vaccines is under way.

SUMMARY

Arboviruses continue to surprise us with unexpected emergence in various locations, the nature of clinical illness, and outcomes. Zika virus presents a classic example of this type of emergence. Ongoing surveillance will be needed to evaluate the long-term pattern of Zika virus and related arboviruses.

Arenaviruses and West Nile Virus in solid organ transplant recipients: Guidelines from the American Society of Transplantation Infectious Diseases Community of Practice

These updated guidelines from the Infectious Diseases Community of Practice of the American Society of Transplantation review the epidemiology, diagnosis, prevention, and management of infection due to Arenaviruses and West Nile Virus (WNV) in the pre- and post-transplant period. Arenaviruses and WNV have been identified as causes of both donor-derived and post-transplant infection. Most data related to these infections have been published in case reports and case series. Transplant recipients may become infected with Arenaviruses if they, or their donors, are exposed to wild rodents or infected pet rodents. Lymphocytic choriomeningitis virus is the most commonly recognized Arenavirus among transplant recipients and should be considered when transplant recipients present with fever, hepatitis, meningitis/encephalitis, and/or multisystem organ failure. WNV is a mosquito-borne virus, and as such, its incidence varies yearly depending on environmental conditions. WNV in transplant recipients typically presents with fever, myalgias, and rash; approximately one in 40 develop neuroinvasive disease. Due to its morbidity, the Organ Procurement and Transplantation Network recently mandated that transplant centers screen living donors for WNV infection in endemic areas. Little is known about the optimal treatment of Arenaviruses or WNV; reduction in immunosuppression and supportive care are the mainstays of management at present.

History and Future of Nucleic Acid Amplification Technology Blood Donor Testing

The introduction of blood donor screening by virus nucleic acid amplification technology (NAT) in the mid to late 1990s was driven by the so-called AIDS and hepatitis C virus (HCV) epidemic, with thousands of recipients of infected blood products and components. Plasma fractionators were the first to introduce NAT testing besides pathogen reduction procedures, to reduce the virus transmission risk through their products. To achieve a similar safety standard, NAT was then also introduced for labile blood components. German transfusion centres were the first to start in-house NAT testing of their donations in pools of up to 96 samples for HCV, hepatitis B virus (HBV), and human immunodeficiency virus-1 (HIV-1). Years later the diagnostics industry provided commercial HCV and HIV-1 and later HBV NAT tests on automated platforms. NAT tests for HIV-2, hepatitis A virus, and Parvovirus B19 followed, again driven by transfusion centres with their in-house tests. When severe acute respiratory syndrome corona virus (SARS-CoV) and West Nile Virus emerged it was the NAT that enabled the manufacturers and transfusion centres to instantly introduce sensitive and specific screening tests. Subsequent automation including sample preparation has significantly reduced the costs and complexity of the procedure and made it affordable to middle income countries as well. Currently more than 60 million donations per year are NAT tested worldwide and the remaining residual risk of virus transmission by blood components and products could be reduced to almost zero. Automation rendered possible the reduction of pool size in conjunction with increased throughput and sensitivity. Thus, antibody and antigen testing may be dispensable in the long run, particularly in the combination of NAT testing with pathogen reduction. There are new technologies on the horizon like digital droplet PCR, next-generation sequencing, lab-on-a-chip, and digital antigen assays, which are comparably sensitive. However, each of these has limitations, either in throughput, costs, automation, time to result, specificity, or the need for NAT as an integral part of the technology. Thus, NAT is still the shortest and most efficient means to the result. Donor screening NAT also contributed significantly to our knowledge on how fast viruses replicate, and on the respective diagnostic window. In conjunction with animal and patient studies, we have learned more about the minimal infectious dose and the epidemics in the donor population.

Prevention of transfusion-transmitted infections

Since the 1970s, introduction of serological assays targeting virus-specific antibodies and antigens has been effective in identifying blood donations infected with the classic transfusion-transmitted infectious agents (TTIs; hepatitis B virus [HBV], HIV, human T-cell lymphotropic virus types I and II, hepatitis C virus [HCV]). Subsequently, progressive implementation of nucleic acid-amplification technology (NAT) screening for HIV, HCV, and HBV has reduced the residual risk of infectious-window-period donations, such that per unit risks are <1 in 1 000 000 in the United States, other high-income countries, and in high-incidence regions performing NAT. NAT screening has emerged as the preferred option for detection of newer TTIs including West Nile virus, Zika virus (ZIKV), and Babesia microti Although there is continual need to monitor current risks due to established TTI, ongoing challenges in blood safety relate primarily to surveillance for emerging agents coupled with development of rapid response mechanisms when such agents are identified. Recent progress in development and implementation of pathogen-reduction technologies (PRTs) provide the opportunity for proactive rather than reactive response to blood-safety threats. Risk-based decision-making tools and cost-effectiveness models have proved useful to quantify infectious risks and place new interventions in context. However, as evidenced by the 2015 to 2017 ZIKV pandemic, a level of tolerable risk has yet to be defined in such a way that conflicting factors (eg, theoretical recipient risk, blood availability, cost, and commercial interests) can be reconciled. A unified approach to TTIs is needed, whereby novel tests and PRTs replace, rather than add to, existing interventions, thereby ameliorating cost and logistical burden to blood centers and hospitals.

Neuroinvasive West Nile Virus Post-Heart Transplantation: A Case Report

First described in the United States in the late 1990s, West Nile virus (WNV) infection following solid organ transplantation is a rare but life-threatening complication. The many ways in which WNV may be acquired, patient specific risk factors, and variability in clinical severity present challenges to health care providers caring for these patients.

An Immunopharmacoinformatics Approach in Development of Vaccine and Drug Candidates for West Nile Virus

An outbreak of West Nile Virus (WNV) like the recent Ebola can be more epidemic and fatal to public health throughout the world. WNV possesses utmost threat as no vaccine or drug is currently available for its treatment except mosquito control. The current study applied the combined approach of immunoinformatics and pharmacoinformatics to design potential epitope-based vaccines and drug candidates against WNV. By analyzing the whole proteome of 2994 proteins, the WNV envelope glycoprotein was selected as a therapeutic target based on its highest antigenicity. After proper assessment “KSFLVHREW” and “ITPSAPSYT” were found to be the most potential T and B-cell epitopes, respectively. Besides, we have designed and validated four novel drugs from a known WNV inhibitor, AP30451 by adopting computational approaches. Toxicity assessment and drug score confirmed the effectiveness of these drug candidates. This in silico research might greatly facilitate the wet lab experiments to develop vaccine and drug against WNV.

Group testing case identification with biomarker information

Screening procedures for infectious diseases, such as HIV, often involve pooling individual specimens together and testing the pools. For diseases with low prevalence, group testing (or pooled testing) can be used to classify individuals as diseased or not while providing considerable cost savings when compared to testing specimens individually. The pooling literature is replete with group testing case identification algorithms including Dorfman testing, higher-stage hierarchical procedures, and array testing. Although these algorithms are usually evaluated on the basis of the expected number of tests and classification accuracy, most evaluations in the literature do not account for the continuous nature of the testing responses and thus invoke potentially restrictive assumptions to characterize an algorithm's performance. Commonly used case identification algorithms in group testing are considered and are evaluated by taking a different approach. Instead of treating testing responses as binary random variables (i.e., diseased/not), evaluations are made by exploiting an assay's underlying continuous biomarker distributions for positive and negative individuals. In doing so, a general framework to describe the operating characteristics of group testing case identification algorithms is provided when these distributions are known. The methodology is illustrated using two HIV testing examples taken from the pooling literature.

Japanese Encephalitis Virus Transmitted Via Blood Transfusion, Hong Kong, China

Japanese encephalitis virus (JEV) is a mosquitoborne virus endemic to China and Southeast Asia that causes severe encephalitis in <1% of infected persons. Transmission of JEV via blood transfusion has not been reported. We report transmission of JEV via blood donation products from an asymptomatic viremic donor to 2 immunocompromised recipients. One recipient on high-dose immunosuppressive drugs received JEV-positive packed red blood cells after a double lung transplant; severe encephalitis and a poor clinical outcome resulted. JEV RNA was detected in serum, cerebrospinal fluid, and bronchoalveolar lavage fluid specimens. The second recipient had leukemia and received platelets after undergoing chemotherapy. This patient was asymptomatic; JEV infection was confirmed in this person by IgM seroconversion. This study illustrates that, consistent with other pathogenic flaviviruses, JEV can be transmitted via blood products. Targeted donor screening and pathogen reduction technologies could be used to prevent transfusion-transmitted JEV infection in highly JEV-endemic areas.

Pathogen reduction and blood transfusion safety in Africa: strengths, limitations and challenges of implementation in low-resource settings

Transfusion-transmitted infection risk remains an enduring challenge to blood safety in Africa. A high background incidence and prevalence of the major transfusion-transmitted infections (TTIs), dependence on high-risk donors to meet demand, suboptimal testing and quality assurance collectively contribute to the increased risk. With few exceptions, donor testing is confined to serological evaluation of human immunodeficiency virus (HIV), hepatitis B and C (HBV and HCV) and syphilis. Barriers to implementation of broader molecular methods include cost, limited infrastructure and lack of technical expertise. Pathogen reduction (PR), a term used to describe a variety of methods (e.g. solvent detergent treatment or photochemical activation) that may be applied to blood following collection, offers the means to diminish the infectious potential of multiple pathogens simultaneously. This is effective against different classes of pathogen, including the major TTIs where laboratory screening is already implemented (e.g. HIV, HBV and HCV) as well pathogens that are widely endemic yet remain unaddressed (e.g. malaria, bacterial contamination). We sought to review the available and emerging PR techniques and their potential application to resource-constrained parts of Africa, focusing on the advantages and disadvantages of such technologies. PR has been slow to be adopted even in high-income countries, primarily given the high costs of use. Logistical considerations, particularly in low-resourced parts of Africa, also raise concerns about practicality. Nonetheless, PR offers a rational, innovative strategy to contend with TTIs; technologies in development may well present a viable complement or even alternative to targeted screening in the future.

Epidemiology of donors and recipients: lessons from the SCANDAT database

With the development of several 'vein-to-vein' databases, which capture data on the entire donor-recipient continuum and link this data to health outcomes, there has been an increasing number of studies investigating the health effects of all aspects of the practice of transfusion medicine. The Scandinavian Donations and Transfusions (SCANDAT) database is one of several such databases, which includes all electronically available data on blood donors, donations and transfusions since the late 1960s in Sweden and the early 1980s in Denmark. The SCANDAT database has been used to characterise disease occurrence among blood donors and transfused patients, as well as to investigate possible health effects of blood donations, aspects of transfusion care and possible transfusion transmission of disease. Recent publications include studies on recipient mortality associated with the storage lesion, studies on the effects of donor demographics on patient mortality and health effects of frequent blood donation. Although this research approach is clearly very powerful, the appropriate analysis of such real-world data is complex and requires close methodological attention. The purpose of this review is to present some of the research conducted within the SCANDAT collaboration. We hope more international collaboration may help improve our understanding of the important remaining questions about donor and recipient health.

Genomic and epidemiological characterisation of a dengue virus outbreak among blood donors in Brazil

Outbreaks caused by Dengue, Zika and Chikungunya viruses can spread rapidly in immunologically naïve populations. By analysing 92 newly generated viral genome sequences from blood donors and recipients, we assess the dynamics of dengue virus serotype 4 during the 2012 outbreak in Rio de Janeiro. Phylogenetic analysis indicates that the outbreak was caused by genotype II, although two isolates of genotype I were also detected for the first time in Rio de Janeiro. Evolutionary analysis and modelling estimates are congruent, indicating a reproduction number above 1 between January and June, and at least two thirds of infections being unnoticed. Modelling analysis suggests that viral transmission started in early January, which is consistent with multiple introductions, most likely from the northern states of Brazil, and with an increase in within-country air travel to Rio de Janeiro. The combination of genetic and epidemiological data from blood donor banks may be useful to anticipate epidemic spread of arboviruses.

Group testing regression models with dilution submodels

Group testing, where specimens are tested initially in pools, is widely used to screen individuals for sexually transmitted diseases. However, a common problem encountered in practice is that group testing can increase the number of false negative test results. This occurs primarily when positive individual specimens within a pool are diluted by negative ones, resulting in positive pools testing negatively. If the goal is to estimate a population-level regression model relating individual disease status to observed covariates, severe bias can result if an adjustment for dilution is not made. Recognizing this as a critical issue, recent binary regression approaches in group testing have utilized continuous biomarker information to acknowledge the effect of dilution. In this paper, we have the same overall goal but take a different approach. We augment existing group testing regression models (that assume no dilution) with a parametric dilution submodel for pool-level sensitivity and estimate all parameters using maximum likelihood. An advantage of our approach is that it does not rely on external biomarker test data, which may not be available in surveillance studies. Furthermore, unlike previous approaches, our framework allows one to formally test whether dilution is present based on the observed group testing data. We use simulation to illustrate the performance of our estimation and inference methods, and we apply these methods to 2 infectious disease data sets.

Correlation of West Nile Virus Incidence in Donated Blood with West Nile Neuroinvasive Disease Rates, United States, 2010-2012

Over the past decade, West Nile virus (WNV) has spread across the United States. We aggregated blood donor data from 2010–2012 and then calculated the incidence of WNV RNA–positive donations and compared the incidence with neuroinvasive disease (NID) case data from the ArboNET surveillance system. Of 10,107,853 donations, 640 were confirmed positive. The seasonal WNV incidence rate per 100,000 persons was 33.4 (95% CI 22–45) in 2010, 25.7 (95% CI 15–34) in 2011, and 119.9 (95% CI 98–141) in 2012. NID to blood donor ratios were 1 in 164 (95% CI 152–178) in 2010, 1 in 158 (95% CI 145–174) in 2011, and 1 in 131 (95% CI 127–136) in 2012. We updated estimates of the ratio of NID to WNV infection rates, demonstrating stable disease penetrance over the study period. Blood donor WNV RNA screening is a valuable public health tool for WNV surveillance.

West Nile Virus Infection in Human and Mouse Cornea Tissue

The purpose of this study was to determine the in vitro and ex vivo susceptibility of human corneal cells to West Nile virus (WNV) infection and evaluate the ability of the virus to disseminate to the corneas of infected mice. Human corneal epithelial cells were challenged with WNV, incubated for 1-6 days, and tested for evidence of WNV infection. Viral RNA and antigen were detected at every time point, and the virus reached a peak titer of 2.5 × 10⁷ plaque-forming units (pfu)/mL at 3 days postinoculation (PI). Corneas procured from donors were incubated in culture dishes containing WNV for 1-5 days and tested for evidence of WNV. Viral RNA and antigen were detected, and the virus reached a mean peak titer of 4.9 × 10⁴ pfu/mL at 5 days PI. Mice were inoculated intraperitoneally with WNV, and their eyes were harvested at 2, 5, and 8 days PI and tested for evidence of WNV. Viral RNA was detected in corneas of four of nine systemically infected mice as early as 2 days PI. We conclude that human corneal cells support WNV replication in vitro and ex vivo, and WNV may disseminate into the corneas of experimentally infected mice. These findings indicate that corneal transmission cannot be ruled out as a novel mode of human-to-human WNV transmission and additional experiments should be conducted to assess this risk further.

Estimating the prevalence of multiple diseases from two-stage hierarchical pooling

Testing protocols in large-scale sexually transmitted disease screening applications often involve pooling biospecimens (e.g., blood, urine, and swabs) to lower costs and to increase the number of individuals who can be tested. With the recent development of assays that detect multiple diseases, it is now common to test biospecimen pools for multiple infections simultaneously. Recent work has developed an expectation-maximization algorithm to estimate the prevalence of two infections using a two-stage, Dorfman-type testing algorithm motivated by current screening practices for chlamydia and gonorrhea in the USA. In this article, we have the same goal but instead take a more flexible Bayesian approach. Doing so allows us to incorporate information about assay uncertainty during the testing process, which involves testing both pools and individuals, and also to update information as individuals are tested. Overall, our approach provides reliable inference for disease probabilities and accurately estimates assay sensitivity and specificity even when little or no information is provided in the prior distributions. We illustrate the performance of our estimation methods using simulation and by applying them to chlamydia and gonorrhea data collected in Nebraska. Copyright © 2016 John Wiley & Sons, Ltd.

Differences in Early Cytokine Production Are Associated With Development of a Greater Number of Symptoms Following West Nile Virus Infection

BACKGROUND

West Nile virus (WNV) is an emerging cause of meningitis and encephalitis in the United States. Although severe neuroinvasive disease and death can occur in rare instances, the majority of infected individuals remain asymptomatic or present with a range of clinical manifestations associated with West Nile fever.

METHODS

To better understand the interindividual variability associated with the majority of WNV infections, we evaluated the association of cytokine/chemokine production and outcome of infection among 115 WNV-positive US blood donors identified in 2008-2011. All subjects self-reported symptoms as having occurred during the 2 weeks following blood donation, using a standardized questionnaire.

RESULTS

We discovered that, prior to seroconversion, an early potent, largely type I interferon-mediated response correlated with development of a greater number of symptoms in WNV-infected individuals. Interestingly, individuals who developed fewer symptoms had not only a more modest type I interferon response initially, but also a protracted cytokine response after seroconversion, marked by the production of monocyte and T-cell-associated chemokines.

CONCLUSIONS

Collectively, our data suggest that, although an early type I interferon response appears to be crucial to control WNV infection, successful immunity may require a modest early response that is maintained during the course of infection.

Zika Virus: Implications for Public Health

The World Health Organization has declared the current Zika virus (ZIKV) epidemic a public health emergency of international concern. Lack of vaccines and reliable diagnostic tests, broad geographical distribution of mosquito species that can transmit the virus, and absence of population immunity in newly affected countries are causes for concern. Although most infected persons are asymptomatic, ZIKV has been associated with a rise in cases of neurological complications and fetal central nervous system malformations. This defines such an arbovirus as something whose transmission should be prevented. This review summarizes the current understanding of ZIKV biology and epidemiology, as well as possible interventions to prevent contagion and transmission.

Climate change projections of West Nile virus infections in Europe: implications for blood safety practices

BACKGROUND

West Nile virus (WNV) is transmitted by mosquitoes in both urban as well as in rural environments and can be pathogenic in birds, horses and humans. Extrinsic factors such as temperature and land use are determinants of WNV outbreaks in Europe, along with intrinsic factors of the vector and virus.

METHODS

With a multivariate model for WNV transmission we computed the probability of WNV infection in 2014, with July 2014 temperature anomalies. We applied the July temperature anomalies under the balanced A1B climate change scenario (mix of all energy sources, fossil and non-fossil) for 2025 and 2050 to model and project the risk of WNV infection in the future. Since asymptomatic infections are common in humans (which can result in the contamination of the donated blood) we estimated the predictive prevalence of WNV infections in the blood donor population.

RESULTS

External validation of the probability model with 2014 cases indicated good prediction, based on an Area Under Curve (AUC) of 0.871 (SD = 0.032), on the Receiver Operating Characteristic Curve (ROC). The climate change projections for 2025 reveal a higher probability of WNV infection particularly at the edges of the current transmission areas (for example in Eastern Croatia, Northeastern and Northwestern Turkey) and an even further expansion in 2050. The prevalence of infection in (blood donor) populations in the outbreak-affected districts is expected to expand in the future.

CONCLUSIONS

Predictive modelling of environmental and climatic drivers of WNV can be a valuable tool for public health practice. It can help delineate districts at risk for future transmission. These areas can be subjected to integrated disease and vector surveillance, outreach to the public and health care providers, implementation of personal protective measures, screening of blood donors, and vector abatement activities.

Safety of the blood supply

BACKGROUND

The transfusion of blood components plays a significant role as supportive therapy in the treatment of patients with cancer. Although blood transfusions help manage complications arising from either the patient's primary condition or associated with therapeutic intervention, their use introduces a new set of risks; therefore, health care professionals must be aware of the potential morbidity introduced by using blood components and endeavor to optimize outcomes by ordering transfusions only when the benefits outweigh the inherent risks.

METHODS

This article sought to review the published literature, including the epidemiology of diseases transmissible via transfusion, performance characteristics for assays used for blood donor screening, surveillance activities to detect newly emergent pathogens, and biovigilance activities reported by public health authorities.

RESULTS

Effective measures have been implemented to significantly decrease the risk of transmissible diseases associated with transfusion. Reports of viral disease transmitted via transfusion have been nearly eliminated, particularly since the introduction of molecular-based detection technology. The transmission of bacteria and parasites still represents a threat to the use of cellular blood components. Transfusion-associated human prion disease has not been reported in the United States. Immune-mediated reactions due to donor-recipient incompatibility remain a challenge.

CONCLUSIONS

Transmissible agents most commonly associated with risks due to transfusion are no longer a major threat; however, a significant challenge remains with regard to addressing the need for quick response mechanisms to manage emerging pathogens with the potential for rapid spread, either unintentionally (eg, globalization) or intentionally (eg, bioterrorism). The use of technology to reduce pathogens holds promise for further increasing the safety profile of blood transfusion.

Bitten by a bug or a bag? Transfusion-transmitted dengue: a rare complication in the bleeding surgical patient

BACKGROUND

Blood-borne infections remain a risk of blood transfusions. While routine screening of donated blood products has greatly reduced the risk of human immunodeficiency virus, hepatitis B, and hepatitis C transmission, arboviruses such as dengue, chikungunya, and the West Nile virus remain significant risks especially during outbreaks.

CASE REPORT

We report a rare case of dengue documented to be acquired through a blood transfusion, which resulted in severe thrombocytopenia prolonging admission in hospital in a neurosurgical patient.

RESULTS

The donor of one of the units of red blood cells presented with dengue fever 2 days after donating. Sanger sequencing confirmed DENV-2 (dengue virus, Serotype 2) in both the donor and the patient samples and showed 100% nucleotide sequence identity between the two viruses, confirming transfusion-transmitted dengue infection.

CONCLUSION

This case highlights the importance of arboviral screening of donor blood, especially for populations in endemic areas during outbreaks.

Latest developments and challenges in the diagnosis of human West Nile virus infection

West Nile virus (WNV) is a mosquito-borne flavivirus responsible for an increasing number of human outbreaks of neuroinvasive disease in Europe and in North America. Notwithstanding the improvements in the knowledge of virus epidemiology and clinical course of infection and the development of new laboratory tests, the diagnosis of WNV infection remains challenging and many cases still remain unrecognized. WNV genome diversity, transient viremia with low viral load and cross-reactivity with other flaviviruses of the antibodies induced by WNV infection are important hurdles that require the diagnosis to be performed by experienced laboratories. Herein, we present and discuss the novel findings on the molecular epidemiology and clinical features of WNV infection in humans with special focus on Europe, the performance of diagnostic tests and the novel methods that have been developed for the diagnosis of WNV infection. A view on how the field might evolve in the future is also presented.

Development of a double antibody sandwich ELISA for West Nile virus detection using monoclonal antibodies against non-structural protein 1

The early diagnosis of West Nile virus (WNV) infection is important for successful clinical management and epidemiological control. The non-structural protein 1 (NS1) of flavivirus, a highly conserved and secreted glycoprotein, is abundant in the serum of flavivirus-infected patients and represents a useful early diagnostic marker. We developed a WNV-specific NS1 antigen-capture ELISA using two mouse monoclonal antibodies (MAbs) that recognised distinct epitopes of the NS1 protein of WNV as capture and detection antibodies. The antigen-capture ELISA displayed exclusive specificity to WNV without cross-reaction with other related members of the flavivirus family, including the dengue virus, yellow fever virus, Japanese encephalitis virus, and tick-borne encephalitis virus. Additionally, the specificity was presented as no false positive in normal (0/1003) and DENV-infected (0/107) human serum specimens. The detection limit of the antigen-capture ELISA was as low as 15 pg/ml of recombinant WNV NS1 protein (rWNV-NS1) and 6.1 plaque-forming units (PFU)/0.1 ml of WNV-infected culture supernatant. In mice infected with WNV, the NS1 protein was readily detected in serum as early as one day after WNV infection, prior to the development of clinical signs of the disease. The sensitivity of the NS1 capture ELISA (93.7%) was significantly higher (79.4%) than that of real-time reverse transcription polymerase chain reaction in 63 serum samples from WNV-infected mice (p = 0.035). This newly developed NS1 antigen-capture ELISA with high sensitivity and specificity could be used as an efficient method for the early diagnosis of WNV infection in animals or humans.

Current epidemiology and clinical practice in arboviral infections - implications on blood supply in South-East Asia

Arthropod-borne viruses (arboviruses) are a growing threat to global health. Complex vector-virus-host interactions lead to unpredictable epidemiological patterns. Difficulties in accurate surveillance including imperfect diagnostic tools impair effective response to outbreaks. With arboviral infections causing a wide spectrum of disease severity, from asymptomatic infection to fatal neuroinvasive and haemorrhagic fevers, the potential impact on blood safety is significant. Asymptomatic or presymptomatic individuals may introduce virus into the blood supply by donation, while recipients can potentially suffer severe consequences. Dengue, West Nile and chikungunya outbreaks have led to responses by blood transfusion services which can inform future planning. Reports of transfusion-associated transmission demonstrate the potentially fatal consequences of lack of haemovigilance. South-East Asia remains vulnerable to arboviruses with permissive climate and high levels of endemic transmission as well as the potential for emerging and re-emerging arboviral diseases. Resource limitations constrain the use of expensive technologies for donor screening. Continued surveillance and research will be required to manage the arboviral threat to the blood supply.

West Nile virus nucleic acid persistence in whole blood months after clearance in plasma: implication for transfusion and transplantation safety

BACKGROUND

Previous reports of West Nile virus (WNV) RNA persistence in blood compartments have raised concerns around the remaining risk of WNV transfusion transmission. This study characterized the dynamics of WNV viremia in blood compartments in a longitudinal cohort of 54 WNV-infected blood donors.

STUDY DESIGN AND METHODS

Blood samples were collected throughout the year after WNV RNA-positive blood donation (index) and characterized for WNV immunoglobulin (Ig)M and IgG antibodies and for WNV RNA by real-time reverse transcription-polymerase chain reaction. WNV viral loads were compared in plasma and whole blood samples and correlated with blood groups and clinical outcomes.

RESULTS

WNV RNA persisted in the red blood cell (RBC) compartment up to 3 months postindex in 42% of the donors. Donors with the highest WNV RNA levels in plasma at index maintained the highest WNV RNA levels in whole blood over the 3 months postindex. Blood group A donors maintained higher postindex WNV viral load in whole blood than blood group O individuals (p = 0.027). Despite a trend for WNV RNA to persist longer in whole blood from symptomatic subjects, no significant association was found between WNV RNA levels in whole blood and disease outcome.

CONCLUSION

This study confirmed that WNV RNA persists in the RBC fraction in whole blood and further suggested that the level of persistence in whole blood may be a reflection of initial viral burden in plasma. The association with blood groups suggests that WNV adherence to RBCs may be mediated by molecules overrepresented at the surface of blood group A RBCs.

Considerations for screening live kidney donors for endemic infections: a viewpoint on the UNOS policy

In February 2013, the Organ Procurement and Transplantation Network mandated that transplant centers perform screening of living kidney donors prior to transplantation for Strongyloides, Trypanosoma cruzi and West Nile virus (WNV) infection if the donor is from an endemic area. However, specific guidelines for screening were not provided, such as the optimal testing modalities, timing of screening prior to donation and the appropriate selection of donors. In this regard, the American Society of Transplantation Infectious Diseases Community of Practice, together with disease-specific experts, has developed this viewpoint document to provide guidance for the testing of live donors for Strongyloides, T. cruzi and WNV infection, specifically identifying at-risk populations and testing algorithms, including advantages, limitations and interpretation of results.

Potential for Zika virus transmission through blood transfusion demonstrated during an outbreak in French Polynesia, November 2013 to February 2014

Since October 2013, French Polynesia has experienced the largest documented outbreak of Zika virus (ZIKAV) infection. To prevent transmission of ZIKAV by blood transfusion, specific nucleic acid testing of blood donors was implemented. From November 2013 to February 2014: 42 (3%) of 1,505 blood donors, although asymptomatic at the time of blood donation, were found positive for ZIKAV by PCR. Our results serve to alert blood safety authorities about the risk of post-transfusion Zika fever.

Two-stage hierarchical group testing for multiple infections with application to the infertility prevention project

Screening for sexually transmitted diseases (STDs) has benefited greatly from the use of group testing (pooled testing) to lower costs. With the development of assays that detect multiple infections, screening practices now involve testing pools of individuals for multiple infections simultaneously. Building on the research for single infection group testing procedures, we examine the performance of group testing for multiple infections. Our work is motivated by chlamydia and gonorrhea testing for the infertility prevention project (IPP), a national program in the United States. We consider a two-stage pooling algorithm currently used to perform testing for the IPP. We first derive the operating characteristics of this algorithm for classification purposes (e.g., expected number of tests, misclassification probabilities, etc.) and identify pool sizes that minimize the expected number of tests. We then develop an expectation-maximization (EM) algorithm to estimate probabilities of infection using both group and individual retest responses. Our research shows that group testing can offer large cost savings when classifying individuals for multiple infections and can provide prevalence estimates that are actually more efficient than those from individual testing.