Clinical and neuroradiologic features of 39 consecutive cases of West Nile Virus meningoencephalitis

West Nile Virus (WNV): One-Health and Eco-Health Global Risks

West Nile virus (WNV) is an important zoonotic pathogen belonging to the Flaviviridae family, which is endemic in some areas and emerging in others. WNV is transmitted by blood-sucking mosquitoes of the genus Culicoides, Aedes, and Anopheles, and the infection can cause different clinical symptoms. The most common and benign illness in humans is West Nile fever (WNF), but a lethal neurological disease (WNND), related to the neuro-invasiveness of WNV lineage 2, represents the highest health risk of WNV infection. The neuro-clinical form is recognized in mammals (land and cetaceans), particularly in humans (elderly or immunosuppressed) and in horses, avian species, and wildlife animals ranging free or in a zoological setting. This review highlights the most relevant data regarding epidemiology, virology, pathogenesis and immunity, clinical signs and differential diagnosis, pathology and imaging, histopathology and gross pathology, economic impact, influence of climate change, and surveillance of WNV. Climate change has favored the wide spread of WNV in many areas of the globe and consequent One-Health and Eco-Health emergencies, influencing the health of human beings, animals, and ecosystems.

Clinical, Prognostic, and Longitudinal Functional and Neuropsychological Features of West Nile Virus Neuroinvasive Disease in the United States: A Systematic Review and Meta-Analysis

OBJECTIVE

West Nile virus (WNV) is the most common cause of arboviral disease in the United States. Approximately 1% of infections involve the nervous system, most commonly resulting in West Nile encephalitis (WNE), West Nile meningitis (WNM), or acute flaccid paralysis (AFP).

METHODS

In this systematic review, we characterized comprehensively the diagnostic and clinical features of WNV neuroinvasive disease (WNND) in the United States, as well as the evidence regarding prognostic factors and long-term outcomes of WNND.

RESULTS

We identified 47 relevant studies reporting data on acute or longitudinal features of WNND. Across studies, the most common presenting symptoms were fever (88%), nausea/vomiting (58%), and fatigue (50%) coupled neurologically with headache (50%), altered mental status (39%), and focal weakness (32%). Pooled mortality was 9.2%, and 42.1% of reported cases required intensive care unit (ICU) admission. In meta-analyses, chronic kidney disease (odds ratio [OR] = 5.99, 95% confidence interval [CI] = 2.71-13.23), diabetes mellitus (OR = 2.43, 95% CI = 1.54-3.84), and hypertension (OR = 4.01, 95% CI = 2.39-6.72) were associated with an increased risk of mortality. Multidomain neurocognitive impairment was reported in several studies at post-hospitalization follow-up, although with marked heterogeneity between study methodology. Subjective neurocognitive impairment, most notably fatigue (37-75%), memory concerns (11-57%), concentration deficits (17-48%), and depression (17-38%), were also common at post-hospitalization follow-up.

INTERPRETATION

These findings underscore the significant mortality and morbidity of WNND in the acute and long-term setting. Our findings may additionally provide utility for risk stratification of hospitalized patients with WNND and suggest the need for further evaluation of novel therapeutics to prevent substantial disease-associated acute and long-term disability. ANN NEUROL 2025.

Acute Flaccid Myelitis Caused by West Nile Virus: A Case Report and Neuroimaging Correlate

West Nile virus (WNV) is the most common mosquito-borne illness in the United States. Most cases remain asymptomatic or may be associated with a mild febrile illness; however, it can invade the central nervous system and cause meningoencephalitis, or rarely, acute flaccid paralysis (AFP). Here, we describe a case of WNV-associated paralysis in a previously healthy male presenting with asymmetric weakness and absent deep tendon reflexes. Magnetic resonance imaging (MRI) of the spine displayed a hyperintensity lesion restricted to the central gray matter, preferentially affecting the ventral horns, which is reflected by his clinical features. This case contributes to mounting evidence that WNV can cause selective injury to the ventral gray matter of the spinal cord and demonstrates that WNV should be considered a unique causative agent in patients presenting with AFP.

Infectious leukoencephalopathies

Leukoencephalopathy from infectious agents may have a rapid course, such as human simplex virus encephalitis; however, in many diseases, it may take months or years before diagnosis, such as in subacute sclerosing panencephalitis or Whipple disease. There are wide geographic distributions and susceptible populations, including both immunocompetent and immunodeficient patients. Many infections have high mortality rates, such as John Cunningham virus and subacute sclerosing panencephalitis, although others have effective treatments if suspected and treated early, such as herpes simplex encephalitis. This chapter will describe viral, bacterial, and protozoal infections, which predominantly cause leukoencephalopathy. We focus on the clinical presentation of these infectious agents briefly covering epidemiology and subtypes of infections. Next, we detail current pathophysiologic mechanisms causing white matter injury. Diagnostic and confirmatory tests are discussed. We cover predominantly MRI imaging features of leukoencephalopathies, and in addition, summarize the common imaging features. Additionally, we detail how imaging features may be used to narrow the differential of a leukoencephalopathy clinical presentation. Lastly, we present an outline of common treatment approaches where available.

West Nile virus encephalomyelitis in an immunocompromised patient

We report a case of a 50-year-old immunocompromised woman who presented with acute encephalopathy and gait ataxia due to severe West Nile virus encephalomyelitis. The patient remarkably improved following early and sustained aggressive immunomodulation. Diagnosing West Nile neuroinvasive disease could be challenging without biochemical evidence of West Nile virus nucleic acid in the cerebrospinal fluid, a specific but not sensitive test. Although the neuroimaging findings in our patient could be considered "typical" for West Nile neuroinvasive disease, there is an overlap with the imaging abnormalities seen in other neuroinflammatory disorders presenting with acute leukoencephalopathy. Hence, we review West Nile neuroinvasive disease imaging characteristics and the differential diagnosis of acute leukoencephalopathy.

Arbovirus and seizures

The high prevalence and spread of arthropod-borne viruses (arboviruses) make them an important cause of viral encephalitis in humans. Most epidemic viral encephalitides have an etiology associated with arboviruses. Among various arboviruses, the Japanese encephalitis virus, West Nile virus, Zika virus, Dengue virus and Chikungunya virus can induce seizures. Arboviruses of the genus Flavivirus are usually transmitted by mosquitoes and other host animals. These vector-borne pathogens can cause epidemic viral encephalitis. Seizures may not be the major manifestation in these viral encephalitides, but may predict a poor prognosis. In this article, we discuss the relationships between these viruses and seizures from perspectives of clinical characteristics, pathogenesis, prognosis and treatments of each.

Emergent Viral Infections of the CNS

Biological evolution of the microbiome continually drives the emergence of human viral pathogens, a subset of which attack the nervous system. The sheer number of pathogens that have appeared, along with their abundance in the environment, demand our attention. For the most part, our innate and adaptive immune systems have successfully protected us from infection; however, in the past 5 decades, through pathogen mutation and ecosystem disruption, a dozen viruses emerged to cause significant neurologic disease. Most of these pathogens have come from sylvatic reservoirs having made the energetically difficult, and fortuitously rare, jump into humans. But the human microbiome is also replete with agents already adapted to the host that need only minor mutations to create neurotropic/toxic agents. While each host/virus symbiosis is unique, this review examines virologic and immunologic principles that govern the pathogenesis of different viral CNS infections that were described in the past 50 years (Influenza, West Nile Virus, Zika, Rift Valley Fever Virus, Hendra/Nipah, Enterovirus-A71/-D68, Human parechovirus, HIV, and SARS-CoV). Knowledge of these pathogens provides us the opportunity to respond and mitigate infection while at the same time prepare for inevitable arrival of unknown agents.

Retrospective Descriptive Analysis of West Nile Neuroinvasive Disease (WNND) in Northwest Louisiana

Aims

The aim of the study was to describe the presentation characteristics and epidemiology of WNND in Louisiana to improve future recognition of cases and decrease inappropriate antibiotic use. Settings and Design. It was a retrospective descriptive-analytic cohort study. A total of 23 patients with WNND were identified at one tertiary care hospital center in Northwest Louisiana from a retrospective chart review from January 1, 2012 to October 31, 2017.

Results

The median age was 49 years (range: 15–75) for patients with WNND. Of 23 patients diagnosed with WNND, twelve (52%) were diagnosed with encephalitis (WNE), six (26%) were diagnosed with meningitis (WNM), and five (22%) with myelitis (WNME). The common symptoms with WNND were fever in 65%, altered mental status in 61%, headache in 52%, fatigue in 43%, gastrointestinal symptoms in 43%, rigors in 30%, imbalance in 26%, rash in 9%, and seizures in 26% of patients. Most patients presented in the late summer season. The average duration of antibiotics given was six days. The average number of days from the admission to the diagnosis of WNND was nine days (3 to 16 days). Twenty-one (91%) patients survived the infection.

Conclusions

Identifying WNV infection early in its clinical course would help in decreasing inappropriate antibiotic use when patients presented with fever and meningeal symptoms. Performing WNV serology in CSF studies is critical in making the diagnosis.

West Nile Virus-Induced Neurologic Sequelae-Relationship to Neurodegenerative Cascades and Dementias

Purpose of Review

West Nile virus (WNV) emerged from Central Africa in the 1990s and is now endemic throughout much of the world. Twenty years after its introduction in the USA, it is becoming apparent that neurological impairments can persist for years following infection. Here, we review the epidemiological data in support of such long-term deficits and discuss possible mechanisms that drive these persistent manifestations.

Recent Findings

Focusing on the recently discovered antimicrobial roles of amyloid and alpha-synuclein, we connect WNV late pathology to overlapping features encountered in neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease. We also summarize new research on microglial activation and engulfment of neural synapses seen in recovered WNV as well as in neurodegenerative diseases, and discuss how loss of integrity of the blood-brain barrier (BBB) may exacerbate this process.

Summary

Neuroinvasive viral infections such as WNV may be linked epidemiologically and mechanistically to neurodegeneration. This may open doors to therapeutic options for hitherto untreatable infectious sequelae; additionally, it may also shed light on the possible infectious etiologies of age-progressive neurodegenerative dementias.

Does intra-individual neurocognitive variability relate to neuroinvasive disease and quality of life in West Nile Virus?

West Nile Virus (WNV) can be a neuroinvasive pathogen that may produce persistent mild-to-moderate neurocognitive impairments in some infected persons. Intra-individual variability (IIV) is an index of a person's performance across a neuropsychological test or battery, which is an indicator of neurocognitive control and integrity of prefrontal systems. The present study examined possible associations of IIV to neurological health and well-being in WNV infection. Participants included 84 adults with a range of clinical WNV disease (31 West Nile Encephalitis, 16 West Nile Meningitis, 37 West Nile Fever) who completed the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). IIV was operationalized as covariance of variation (CoV), or the intra-individual standard deviation across 5 age-adjusted RBANS standard scores divided by the mean of standard scores. Participants were assessed for health-related quality of life (QoL) using the RAND 36-item short form health survey (SF-36). Analyses revealed that the West Nile Encephalitis group had higher neurocognitive CoV compared to the West Nile Fever group, and this difference was associated with a medium effect size (Cohen's d = .52). Mixed linear models controlling for estimated IQ, activities of daily living, depression, neuroinvasive disease groups, and fatigue showed that higher RBANS CoV was associated with lower physical, but not mental health QoL. In persons with WNV infection, there is a modest association between elevations in IIV and encephalitis, and even subtle disruptions in neuropsychological functioning show relationships with important self-reported functioning as measured by physical health quality of life. Future studies should examine whether IIV predicts long-term health outcomes (e.g., mortality) in individuals infected with WNV.

Southern California neuroinvasive West Nile virus case series

Approximately 80% of individuals infected with West Nile virus (WNV) are asymptomatic, and less than 1% suffer from neuroinvasion that can result in permanent neurological deficits or mortality. Our institution's location in southern California predisposes it to a sizable case volume of neuroinvasive WNV. A 2-year retrospective study was performed at the Olive View-UCLA Medical Center to identify patients with confirmed WNV infection with neuroinvasion. Patient demographics, neurological exam findings, and laboratory diagnostics were reviewed. Data were tabulated and are presented as percentage, mean ± standard deviation, or median [range]. Twenty-two patients (36.4% female, age 50.2 ± 10.6 years) were identified between 20 August 2012 and 24 September 2013. The most common positive findings on review of symptoms included fever (81.8%), nausea/vomiting (81.8%), and headache (68.2%). Thirteen patients (59.1%) presented with fever defined as ≥ 37.8 °C. Motor strength was reduced in nine patients (40.9%) and eight patients (36.4%) were hyporeflexive. Lumbar puncture was performed in all but three patients (cerebrospinal fluid [CSF] protein 76.8 ± 29.6 mg/dL and glucose 71.0 ± 18.8 mg/dL). Elevated CSF anti-WNV IgM and IgG antibody was detected in 93.8% and 62.5% of the 16 tested cases, respectively. Elevated serum anti-WNV IgM and IgG antibody was detected in 100% and 72.2% of the 18 tested cases, respectively. Encephalitic presentations, with or without focal neurological deficits (e.g., motor weakness, hypotonia), dominated this series. In endemic areas, seasonal presentation of such symptoms should raise suspicion for WNV with neuroinvasion.

West Nile Virus Infection

Although long recognized as a human pathogen, West Nile virus (WNV) emerged as a significant public health problem following its introduction and spread across North America. Subsequent years have seen a greater understanding of all aspects of this viral infection. The North American epidemic resulted in a further understanding of the virology, pathogenesis, clinical features, and epidemiology of WNV infection. Approximately 80% of human WNV infections are asymptomatic. Most symptomatic people experience an acute systemic febrile illness; less than 1% of infected people develop neuroinvasive disease, which typically manifests as meningitis, encephalitis, or anterior myelitis resulting in acute flaccid paralysis. Older age is associated with more severe illness and higher mortality; other risk factors for poor outcome have been challenging to identify. In addition to natural infection through mosquito bites, transfusion- and organ transplant-associated infections have occurred. Since there is no definitive treatment for WNV infection, protection from mosquito bites and other preventative measures are critical. WNV has reached an endemic pattern in North America, but the future epidemiologic pattern is uncertain.

Long-term sequelae of West Nile virus-related illness: a systematic review

We systematically reviewed the clinical outlook of West Nile virus (WNV)-related illness in North America and western Europe. As of March, 2015, more than 45 000 cases of WNV-related illness have been reported in North America. Unlike acute morbidity and mortality, the long-term physical, cognitive, and functional sequelae associated with WNV-related illness are not well characterised. An understanding of WNV-related sequelae and their prognostic factors can support physicians with early diagnosis and tertiary prevention efforts. We searched Ovid Medline, Embase, Scopus, and Environment Complete for studies published between 1999 and 2015. We included 67 studies in our Review. Although muscle weakness, memory loss, and difficulties with activities of daily living were among the most common physical, cognitive, and functional sequelae, respectively, some population groups were reported to be at greater risk of severe neurological disease or death (ie, older men with underlying illnesses such as cardiovascular disease or cancer). A high level of heterogeneity was reported among studies included in this Review, suggesting a need for consistent methods for collecting data and reporting findings. Further, more than half of the studies reporting sequelae relied exclusively on subjective assessment and only two studies used matched control groups. Therefore, opportunities exist for more robust primary studies in future research.

The global ecology and epidemiology of West Nile virus

Since its initial isolation in Uganda in 1937 through the present, West Nile virus (WNV) has become an important cause of human and animal disease worldwide. WNV, an enveloped virus of the genus Flavivirus, is naturally maintained in an enzootic cycle between birds and mosquitoes, with occasional epizootic spillover causing disease in humans and horses. The mosquito vectors for WNV are widely distributed worldwide, and the known geographic range of WNV transmission and disease has continued to increase over the past 77 years. While most human infections with WNV are asymptomatic, severe neurological disease may develop resulting in long-term sequelae or death. Surveillance and preventive measures are an ongoing need to reduce the public health impact of WNV in areas with the potential for transmission.

Rare ocular manifestation in a case of West Nile virus meningoencephalitis

West Nile Virus (WNV) is an arthropod-borne flavivirus, which causes flu-like illness and is sporadically associated with encephalitis. Transmission to humans occurs following a bite from an infected mosquito, which acquires the virus after feeding on dead birds. WNV meningoencephalitis is a rare infection with a neuroinvasive disease occurring in less than 1% of the cases, with varied presentations including aseptic meningitis, meningoencephalitis, and acute flaccid paralysis. Chorioretinitis is the most common eye finding in this infection, while other ocular manifestations have been rarely reported in the literature. We present the first case report of WNV meningoencephalitis, with rare ocular manifestations of acute hemorrhagic conjunctivitis, bilateral subconjunctival hemorrhages, and nystagmus. The rare ocular findings of acute hemorrhagic conjunctivitis, bilateral subconjunctival hemorrhages, and nystagmus diagnosed in our case can guide clinicians toward early diagnosis of WNV meningoencephalitis, while serologic testing is still pending.

Clinical characteristics and functional outcome of patients with West Nile neuroinvasive disease in Serbia

Neurologic manifestations are prominent characteristic of West Nile virus (WNV) infection. The aim of this article was to describe neurological manifestations in patients with WNV neuroinvasive disease and their functional outcome at discharge in the first human outbreak of WNV infection in Serbia. The study enrolled patients treated in the Clinic for Infectious and Tropical Diseases, Clinical Center Serbia in Belgrade, with serological evidence of acute WNV infection who presented with meningitis, encephalitis and/or acute flaccid paralyses (AFP). Functional outcome at discharge was assessed using modified Rankin Scale (mRS) and Barthel index. Fifty-two patients were analysed. Forty-four (84.6 %) patients had encephalitis, eight (15.4 %) had meningitis, and 13 (25 %) had AFP. Among patients with AFP, 12 resembled poliomyelitis and one had clinical and electrodiagnostic findings consistent with polyradiculoneuritis. Among patients with encephalitis, 17 (32.7 %) had clinical signs of rhombencephalitis, and eight (15.4 %) presented with cerebellitis. Respiratory failure with subsequent mechanical ventilation developed in 13 patients with WNE (29.5 %). Nine (17.3 %) patients died, five (9.6 %) were functionally dependent (mRS 3-5), and 38 (73.1 %) were functionally independent at discharge (mRS 0-2). In univariate analysis, the presence of AFP, respiratory failure and consciousness impairment were found to be predictors of fatal outcome in patients with WNV neuroinvasive disease (p < 0.001, p < 0.001, p = 0.018, respectively). The outbreak of human WNV infection in Serbia caused a notable case fatality ratio, especially in patients with AFP, respiratory failure and consciousness impairment. Rhombencephalitis and cerebellitis could be underestimated presentations of WNV neuroinvasive disease.

Clinical manifestations and outcomes of West Nile virus infection

Since the emergence of West Nile virus (WNV) in North America in 1999, understanding of the clinical features, spectrum of illness and eventual functional outcomes of human illness has increased tremendously. Most human infections with WNV remain clinically silent. Among those persons developing symptomatic illness, most develop a self-limited febrile illness. More severe illness with WNV (West Nile neuroinvasive disease, WNND) is manifested as meningitis, encephalitis or an acute anterior (polio) myelitis. These manifestations are generally more prevalent in older persons or those with immunosuppression. In the future, a more thorough understanding of the long-term physical, cognitive and functional outcomes of persons recovering from WNV illness will be important in understanding the overall illness burden.

Viral encephalitis in the ICU

Viral encephalitis causes an altered level of consciousness, which may be associated with fever, seizures, focal deficits, CSF pleocytosis, and abnormal neuroimaging. Potential pathogens include HSV, VZV, enterovirus, and in some regions, arboviruses. Autoimmune (eg, anti-NMDA receptor) and paraneoplastic encephalitis are responsible for some cases where no pathogen is identified. Indications for ICU admission include coma, status epilepticus and respiratory failure. Timely initiation of anti-viral therapy is crucial while relevant molecular and serological test results are being performed. Supportive care should be directed at the prevention and treatment of cerebral edema and other physiological derangements which may contribute to secondary neurological injury.

Two case reports of neuroinvasive west nile virus infection in the critical care unit

We describe the clinical course of two cases of neuroinvasive West Nile Virus (WNV) infection in the critical care unit. The first case is a 70-year-old man who presented during summer with mental status changes. Cerebrospinal fluid (CSF) analysis revealed pleocytosis with lymphocyte predominance. WNV serology was positive in the CSF. His condition worsened with development of left-sided weakness and deterioration of mental status requiring intensive care. The patient gradually improved and was discharged with residual left-sided weakness and near-complete improvement in his mental status. The second case is an 81-year-old man who presented with mental status changes, fever, lower extremity weakness, and difficulty in walking. CSF analysis showed pleocytosis with neutrophil predominance. WNV serology was also positive in CSF. During the hospital stay his mentation worsened, eventually requiring intubation for airway protection and critical care support. The patient gradually improved and was discharged with residual upper and lower extremity paresis. Neuroinvasive WNV infection can lead to significant morbidity, especially in the elderly. These cases should be suspected in patients with antecedent outdoor activities during summer. It is important for critical care providers to be aware of and maintain a high clinical suspicion of this disease process.

Persistent neuropsychological impairment associated with West Nile virus infection

West Nile virus infection can result in prolonged subjective complaints of cognitive and functional decline even in the absence of a neuroinvasive form of infection. Persistent cognitive and functional complaints could be a result of general somatic symptoms, emotional distress, or residual central nervous system damage or dysfunction. Most studies of cognition in postacute West Nile virus infection rely on self-report. This descriptive study aimed to document cognitive deficits in a sample of the 2003 infected population reported in New Mexico. Patients with clinically defined neuroinvasive disease or who were impaired on brief mental status screening were seen for comprehensive neuropsychological assessment. We found that one year after symptom onset, more than half of the sample had objectively measurable neuropsychological impairment in at least two cognitive domains. Impairment was not related to subjective complaints of physical or emotional distress, or premorbid intellectual abilities. Persistent cognitive impairment in West Nile virus infection may be due to prolonged or permanent damage to the central nervous system.

West nile virus neuroinvasive disease

West Nile virus (WNV), first recognized in North America in 1999, was responsible for the largest arboviral epidemic of human encephalitis in history and continues to be the most frequent cause of epidemic meningoencephalitis in North America. WNV neuroinvasive disease (WNND) occurs in fewer than 1% of infected individuals, with presentations including aseptic meningitis, encephalitis, and poliomyelitis. Between 1999 and 2009, over 12,000 cases of WNND were reported in the United States, with the peak annual incidence occurring in epidemics of 2002 and 2003. In this review, we first summarize the epidemiology of WNV over the past decade and the salient clinical features of WNND, including a discussion of laboratory and radiographic findings, risk factors, morbidity, and mortality. In addition, we review recent progress in our understanding of virus and host determinants of the pathogenesis of WNND, as well as the prospects for the development of specific therapeutic targets.

The virology, epidemiology, and clinical impact of West Nile virus: a decade of advancements in research since its introduction into the Western Hemisphere

West Nile virus (WNV) is now endemic in the USA. After the widespread surge of virus activity across the USA, research has flourished, and our knowledge base has significantly expanded over the past 10 years since WNV was first recognized in New York City. This article provides a review of the virology of WNV, history, epidemiology, clinical features, pathology of infection, the innate and adaptive immune response, host risk factors for developing severe disease, clinical sequelae following severe disease, chronic infection, and the future of prevention.

West Nile virus

West Nile virus (WNV) is responsible for thousands of cases of morbidity and mortality in birds, horses, and humans. Epidemics were localized to Europe, Africa, the Middle East, and parts of Asia, and primarily caused a mild febrile illness in humans. In the late 1990s, the virus became more virulent and spread to North America. In humans, the clinical presentation ranges from asymptomatic, seen frequently, to encephalitis/paralysis and death, seen rarely. There is no FDA (Food and Drug Administration)-licensed vaccine for human use, and the only recommended treatment is supportive care. Often, there is a long recovery period. This article reviews the current literature summarizing the molecular virology, epidemiology, clinical manifestations, pathogenesis, diagnosis, treatment, immunology, and protective measures against WNV and WNV infections in humans.

[Second epidemic of West Nile virus meningoencephalitis in Tunisia]

The West Nile virus (WNV) re-emerged in Tunisia in 2003, causing an outbreak of meningoencephalitis.

OBJECTIVE

The authors studied the epidemiological, clinical, biological, and imaging features of WNV-associated neurological disease observed in central eastern Tunisia.

DESIGN

A retrospective descriptive study was made on patients with West Nile meningitis and/or encephalitis observed in the Sousse area, from August 15 to November 15, 2003. Screening for specific anti-WNV antibodies in serum was performed with Elisa.

RESULTS

Recent central nervous system infection due to WNV was confirmed in 21 patients with a mean age of 53 years and a sex ratio of 3.2. The clinical presentation was meningitis in 11 cases, meningoencephalitis in seven cases, and encephalitis in three cases. Patients with encephalitis were older than those with meningitis. An acute flaccid limb paralysis was observed in three patients. The CSF assay showed lymphocytosis, high protein (67 %), and normal glucose levels (83 %). Brain CT scan and MRI were normal. Three patients died, the remaining evolved uneventfully.

CONCLUSIONS

These first cases of WNV meningoencephalitis in Sousse area suggest a possibility of reemergence of this infection. Preventive measures and epidemiological surveillance are necessary.

Systemic distribution of West Nile virus infection: postmortem immunohistochemical study of six cases

Rare cases of West Nile virus (WNV)-associated inflammation outside the central nervous system (CNS) have been reported. We evaluated the systemic distribution of WNV in postmortem tissues during encephalitis in six patients using immunohistochemistry. WNV antigens were detected in neurons of CNS (all 6 cases), kidney (4 cases), lungs (2 cases), pancreas (2 cases), thyroid (2 cases), intestine (2 cases), stomach (1 case), esophagus (1 case), bile duct (1 case), skin (1 case), prostate (1 case) and testis (1 case). In systemic organs epithelial cells were infected. In none of the six cases were viral antigens identified in hepatocytes, heart, adrenal gland, nerves, skeletal muscles, bone, vessels and fat. All cases in which viral antigens were identified in systemic organs in addition to CNS were severely immunocompromised transplant recipients. With the exception of testis and brain, most foci of infection were not associated with inflammation. While the absence of inflammation may in part be due to patient immunosuppression or to possible transient nature of any host response, compartmentalization of viral antigen to the luminal region of epithelial cells may sequester WNV from immune recognition. Comparison of our findings with previous reports suggests that patients with WNV encephalitis can have widespread systemic infection.

Maculopapular rash and tremor are associated with West Nile fever and neurological syndromes

The clinical features associated with West Nile virus (WNV) infections are described based on data collected from history forms submitted with samples during a province-wide WNV testing programme. Age 40-59 years (OR 1.7, p<0.008), residence in the southeast of Alberta (OR 4.2, p<0.001), maculopapular rash (OR 8.6, p<0.001) or tremor (OR 3.6, p<0.001) were independently associated with WNV infection.

West Nile virus neuroinvasive disease

Since 1999, there have been nearly 20,000 cases of confirmed symptomatic West Nile virus (WNV) infection in the United States, and it is likely that more than 1 million people have been infected by the virus. WNV is now the most common cause of epidemic viral encephalitis in the United States, and it will likely remain an important cause of neurological disease for the foreseeable future. Clinical syndromes produced by WNV infection include asymptomatic infection, West Nile Fever, and West Nile neuroinvasive disease (WNND). WNND includes syndromes of meningitis, encephalitis, and acute flaccid paralysis/poliomyelitis. The clinical, laboratory, and diagnostic features of these syndromes are reviewed here. Many patients with WNND have normal neuroimaging studies, but abnormalities may be present in areas including the basal ganglia, thalamus, cerebellum, and brainstem. Cerebrospinal fluid invariably shows a pleocytosis, with a predominance of neutrophils in up to half the patients. Diagnosis of WNND depends predominantly on demonstration of WNV-specific IgM antibodies in cerebrospinal fluid. Recent studies suggest that some WNV-infected patients have persistent WNV IgM serum and/or cerebrospinal fluid antibody responses, and this may require revision of current serodiagnostic criteria. Although there is no proven therapy for WNND, several vaccines and antiviral therapy with antibodies, antisense oligonucleotides, and interferon preparations are currently undergoing human clinical trials. Recovery from neurological sequelae of WNV infection including cognitive deficits and weakness may be prolonged and incomplete.

Mental status after West Nile virus infection

Mental status after acute West Nile virus infection has not been examined objectively. We compared Telephone Interview for Cognitive Status scores of 116 patients with West Nile fever or West Nile neuroinvasive disease. Mental status was poorer and cognitive complaints more frequent with West Nile neuroinvasive disease (p = 0.005).

Mental status after West Nile virus infection

Mental status after acute West Nile virus infection has not been examined objectively. We compared Telephone Interview for Cognitive Status scores of 116 patients with West Nile fever or West Nile neuroinvasive disease. Mental status was poorer and cognitive complaints more frequent with West Nile neuroinvasive disease (p = 0.005).

West Nile virus meningoencephalitis

Since its first appearance in the US in 1999, West Nile virus (WNV) has emerged as the most common cause of epidemic meningoencephalitis in North America. In the 6 years following the 1999 outbreak, the geographic range and burden of the disease in birds, mosquitoes and humans has greatly expanded to include the 48 contiguous US and 7 Canadian provinces, as well as Mexico, the Caribbean islands and Colombia. WNV has shown an increasing propensity for neuroinvasive disease over the past decade, with varied presentations including meningitis, encephalitis and acute flaccid paralysis. Although neuroinvasive disease occurs in less than 1% of infected individuals, it is associated with high mortality. From 1999-2005, more than 8,000 cases of neuroinvasive WNV disease were reported in the US, resulting in over 780 deaths. In this review, we discuss epidemiology, risk factors, clinical features, diagnosis and prognosis of WNV meningoencephalitis, along with potential treatments.

A human-health risk assessment for West Nile virus and insecticides used in mosquito management

West Nile virus (WNV) has been a major public health concern in North America since 1999, when the first outbreak in the Western Hemisphere occurred in New York City. As a result of this ongoing disease outbreak, management of mosquitoes that vector WNV throughout the United States and Canada has necessitated using insecticides in areas where they traditionally have not been used or have been used less frequently. This has resulted in concerns by the public about the risks from insecticide use. The objective of this study was to use reasonable worst-case risk assessment methodologies to evaluate human-health risks for WNV and the insecticides most commonly used to control adult mosquitoes. We evaluated documented health effects from WNV infection and determined potential population risks based on reported frequencies. We determined potential acute (1-day) and subchronic (90-day) multiroute residential exposures from each insecticide for several human subgroups during a WNV disease outbreak scenario. We then compared potential insecticide exposures to toxicologic and regulatory effect levels. Risk quotients (RQs, the ratio of exposure to toxicologic effect) were < 1.0 for all subgroups. Acute RQs ranged from 0.0004 to 0.4726, and subchronic RQs ranged from 0.00014 to 0.2074. Results from our risk assessment and the current weight of scientific evidence indicate that human-health risks from residential exposure to mosquito insecticides are low and are not likely to exceed levels of concern. Further, our results indicate that, based on human-health criteria, the risks from WNV exceed the risks from exposure to mosquito insecticides.

Manifestations of West Nile neuroinvasive disease

Since its introduction to North America in 1999, West Nile virus, an arthropod-borne flavivirus, has become the most significant cause of epidemic encephalitis in the western hemisphere. While most human infections with the virus are asymptomatic and the majority of symptomatic persons experience febrile illness, severe neurologic manifestations, including meningitis, encephalitis, and poliomyelitis may be seen. This review summarizes the virology, epidemiology and pathogenesis of human infection with West Nile virus, and details recent advances in our understanding of the pathophysiology and various clinical manifestations of infection.

Characteristics of the rash associated with West Nile virus fever

We characterized rash in 15 patients with West Nile virus (WNV) fever. Generalized, maculopapular rash typically occurred on days 5-12 of illness. Dysesthesia was reported by 27% of patients, and pruritus by 33% of patients. Because the rash was nonspecific and serologic test results were often negative for WNV at presentation, convalescent-phase testing was frequently required to diagnose WNV fever.

Use of Interferon- in Patients with West Nile Encephalitis: Report of 2 Cases

We describe 2 patients with West Nile virus (WNV) encephalitis who were treated experimentally with interferon (IFN)-alpha. Both patients demonstrated substantial improvement in mentation and speech on the second day of experimental therapy, and neither required endotracheal intubation or admission to the intensive care unit during hospitalization. Moreover, during the 9-month follow-up period, one patient achieved complete recovery, and the other nearly achieved complete resolution of sequelae. To our knowledge, this is the first published report of the use of IFN-alpha to treat WNV encephalitis. Clinical trials are underway to further define the role of this therapy in persons with WNV encephalitis.