Incidence of West Nile virus infection in the Dallas–Fort Worth metropolitan area during the 2012 epidemic

Correcting for Antibody Waning in Cumulative Incidence Estimation From Sequential Serosurveys

Serosurveys are a widely used tool to estimate the cumulative incidence-the fraction of a population that has been infected by a given pathogen. These surveys rely on serological assays that measure the level of pathogen-specific antibodies. Because antibody levels are waning, the fraction of previously infected individuals that have seroreverted increases with time past infection. To avoid underestimating the true cumulative incidence, it is therefore essential to correct for waning antibody levels. We present an empirically supported approach for seroreversion correction in cumulative incidence estimation when sequential serosurveys are conducted in the context of a newly emerging infectious disease. The correction is based on the observed dynamics of antibody titers in seropositive cases and validated using several in silico test scenarios. Furthermore, through this approach we revise a previous cumulative incidence estimate relying on the assumption of an exponentially declining probability of seroreversion over time, of severe acute respiratory syndrome coronavirus 2, of 76% in Manaus, Brazil, by October 2020 to 47.6% (95% confidence region: 43.5-53.5). This estimate has implications, for example, for the proximity to herd immunity in Manaus in late 2020.

The Recipient Epidemiology and Donor Evaluation Study-IV-Pediatric (REDS-IV-P): A research program striving to improve blood donor safety and optimize transfusion outcomes across the lifespan

BACKGROUND

The Recipient Epidemiology and Donor Evaluation Study-IV-Pediatric (REDS-IV-P) is a new iteration of prior National Heart, Lung, and Blood Institute (NHLBI) REDS programs that focus on improving transfusion recipient outcomes across the lifespan as well as the safety and availability of the blood supply.

STUDY DESIGN AND METHODS

The US program includes blood centers and hospitals (22 including 6 free-standing Children's hospitals) in four geographic regions. The Brazilian program has 5 participating hemocenters. A Center for Transfusion Laboratory Studies (CTLS) and a Data Coordinating Center (DCC) support synergistic studies and activities over the 7-year REDS-IV-P program.

RESULTS

The US is building a centralized, vein-to-vein (V2V) database, linking information collected from blood donors, their donations, the resulting manufactured components, and data extracts from hospital electronic medical records of transfused and non-transfused patients. Simultaneously, the Brazilian program is building a donor, donation, and component database. The databases will serve as the backbone for retrospective and prospective observational studies in transfusion epidemiology, transfusion recipient outcomes, blood component quality, and emerging blood safety issues. Special focus will be on preterm infants, patients with sickle cell disease, thalassemia or cancer, and the effect of donor biologic variability and component manufacturing on recipient outcomes. A rapid response capability to emerging safety threats has resulted in timely studies related to Severe Acute Respiratory Syndrome Corona Virus-2 (SARS-CoV-2).

CONCLUSIONS

The REDS-IV-P program endeavors to improve donor-recipient-linked research with a focus on children and special populations while also maintaining the flexibility to address emerging blood safety issues.

Estimation of time-dependent arbovirus infection risk in blood and tissue donations

West Nile virus (WNV) outbreaks raise the concern of WNV infection in donated blood and blood products destined for transfusion. We describe methods we developed to estimate time-dependent risk of WNV infection in donated blood, including improvements not previously detailed. The methods are then extended for use in estimation of the risk of WNV infection in donated cadaveric tissues by introducing stratification and stratum-specific weighting to address novel aspects of this application. Data from the WNV outbreak in Colorado in 2003 are used to estimate risk for donated cardiac tissue.

Epidemiology of West Nile Virus in the United States: Implications for Arbovirology and Public Health

Since West Nile virus (WNV) emerged in the United States in 1999, 22,999 neuroinvasive disease cases in humans were reported through 2017. These cases have arisen from an estimated seven million human infections. Population incidence is geographically heterogeneous and is highest in the West and Midwest. Upwards of 2% of the population in some jurisdictions may become infected during outbreaks. Before universal screening of the United States blood supply, this high infection incidence and that approximately 75% of those infected remain asymptomatic translated into a considerable risk of WNV transfusion transmission despite the short duration of viremia following infection. Universal blood donor screening has nearly eliminated the risk of WNV transfusion transmission, but at enormous cost. WNV transmission via transplanted organs carries extremely high morbidity and mortality. Improved vector surveillance and timely and effective response to surveillance data can reduce the impact of WNV and should remain public health priorities.

Cumulative Incidence of West Nile Virus Infection, Continental United States, 1999-2016

Using reported case data from ArboNET and previous seroprevalence data stratified by age and sex, we conservatively estimate that ≈7 million persons in the United States have been infected with West Nile virus since its introduction in 1999. Our data support the need for public health interventions and improved surveillance.

Forecasting the West Nile Virus in the United States: An Extensive Novel Data Streams-Based Time Series Analysis and Structural Equation Modeling of Related Digital Searching Behavior

BACKGROUND

West Nile virus is an arbovirus responsible for an infection that tends to peak during the late summer and early fall. Tools monitoring Web searches are emerging as powerful sources of data, especially concerning infectious diseases such as West Nile virus.

OBJECTIVE

This study aimed at exploring the potential predictive power of West Nile virus-related Web searches.

METHODS

Different novel data streams, including Google Trends, WikiTrends, YouTube, and Google News, were used to extract search trends. Data regarding West Nile virus cases were obtained from the Centers for Disease Control and Prevention. Data were analyzed using regression, times series analysis, structural equation modeling, and clustering analysis.

RESULTS

In the regression analysis, an association between Web searches and "real-world" epidemiological figures was found. The best seasonal autoregressive integrated moving average model with explicative variable (SARIMAX) was found to be (0,1,1)x(0,1,1)4. Using data from 2004 to 2015, we were able to predict data for 2016. From the structural equation modeling, the consumption of West Nile virus-related news fully mediated the relation between Google Trends and the consumption of YouTube videos, as well as the relation between the latter variable and the number of West Nile virus cases. Web searches fully mediated the relation between epidemiological figures and the consumption of YouTube videos, as well as the relation between epidemiological data and the number of accesses to the West Nile virus-related Wikipedia page. In the clustering analysis, the consumption of news was most similar to the Web searches pattern, which was less close to the consumption of YouTube videos and least similar to the behavior of accessing West Nile virus-related Wikipedia pages.

CONCLUSIONS

Our study demonstrated an association between epidemiological data and search patterns related to the West Nile virus. Based on this correlation, further studies are needed to examine the practicality of these findings.

Neurological disease caused by flavivirus infections

The Flavivirus genus contains dozens of species with varying geographical distributions. Most flavivirus infections in humans are asymptomatic or manifest as a non-specific febrile illness, sometimes accompanied by rash or arthralgia. Certain species are more commonly associated with neurological disease and may be termed neurotropic flaviviruses. Several flaviviruses endemic to Australia and our near northern neighbours are neurotropic, such as Murray Valley encephalitis virus, West Nile (Kunjin) virus and Japanese encephalitis virus. Flavivirus neurological disease ranges from self-limiting meningitis to fulminant encephalitis causing permanent debilitating neurological sequelae or death. The recent Zika virus outbreak in South America has highlighted the dramatic effects of flavivirus neurotropism on the developing brain. This article focuses on the neurotropic flaviviruses endemic to Australia and those of international significance.

Determining the rate of underrecognition of West Nile virus neurologic disease in the province of Quebec in 2012

BACKGROUND

During a major outbreak of West Nile virus (WNV) infection in the province of Quebec in 2012, public health authorities (PHAs) suspected underrecognition of West Nile neurologic disease (WNND). With data on acute infections detected in blood donors, an estimate of the degree of underrecognition was produced.

STUDY DESIGN AND METHODS

All 2012 donors were tested for WNV infection with the use of reverse transcription-polymerase chain reaction (RT-PCR). With the number of cases detected, the number of donors tested, our estimate of the duration of viremia, an estimate of the population at risk, and the ratio of WNND to total cases, an expected number of WNND cases was calculated. A Monte Carlo simulation was used to estimate the range of several of these variables.

RESULTS

Seventeen RT-PCR-positive donors were found among 52,309 donations tested. In the base case, the total number of cases was 16,095 and the expected number of WNND cases was 115. In the Monte Carlo simulation, the mean number of expected WNND cases was 136, and the median was 129. Since only 85 cases were reported to PHAs, it is estimated that between 26 and 37.5% of cases occurring in the province went undetected.

CONCLUSION

The observation that close to one-third of cases of WNND went undetected because of the omission of appropriate laboratory testing indicates the need for improvement in the investigation of acute neurologic syndrome of suspected infectious etiology in Québec.

Age-related alterations in immune responses to West Nile virus infection

West Nile virus (WNV) is the most important causative agent of viral encephalitis worldwide and an important public health concern in the United States due to its high prevalence, severe disease, and the absence of effective treatments. Infection with WNV is mainly asymptomatic, but some individuals develop severe, possibly fatal, neurological disease. Individual host factors play a role in susceptibility to WNV infection, including genetic polymorphisms in key anti-viral immune genes, but age is the most well-defined risk factor for susceptibility to severe disease. Ageing is associated with distinct changes in immune cells and a decline in immune function leading to increased susceptibility to infection and reduced responses to vaccination. WNV is detected by pathogen recognition receptors including Toll-like receptors (TLRs), which show reduced expression and function in ageing. Neutrophils, monocyte/macrophages and dendritic cells, which first recognize and respond to infection, show age-related impairment of many functions relevant to anti-viral responses. Natural killer cells control many viral infections and show age-related changes in phenotype and functional responses. A role for the regulatory receptors Mertk and Axl in blood-brain barrier permeability and in facilitating viral uptake through phospholipid binding may be relevant for susceptibility to WNV, and age-related up-regulation of Axl has been noted previously in human dendritic cells. Understanding the specific immune parameters and mechanisms that influence susceptibility to symptomatic WNV may lead to a better understanding of increased susceptibility in elderly individuals and identify potential avenues for therapeutic approaches: an especially relevant goal, as the world's populating is ageing.