Severe Neuroinvasive West Nile Virus Infection in a Child with Undiagnosed Addison's Disease

Autoantibodies neutralizing type I IFNs underlie West Nile virus encephalitis in ∼40% of patients

Mosquito-borne West Nile virus (WNV) infection is benign in most individuals but can cause encephalitis in <1% of infected individuals. We show that ∼35% of patients hospitalized for WNV disease (WNVD) in six independent cohorts from the EU and USA carry auto-Abs neutralizing IFN-α and/or -ω. The prevalence of these antibodies is highest in patients with encephalitis (∼40%), and that in individuals with silent WNV infection is as low as that in the general population. The odds ratios for WNVD in individuals with these auto-Abs relative to those without them in the general population range from 19.0 (95% CI 15.0-24.0, P value <10-15) for auto-Abs neutralizing only 100 pg/ml IFN-α and/or IFN-ω to 127.4 (CI 87.1-186.4, P value <10-15) for auto-Abs neutralizing both IFN-α and IFN-ω at a concentration of 10 ng/ml. These antibodies block the protective effect of IFN-α in Vero cells infected with WNV in vitro. Auto-Abs neutralizing IFN-α and/or IFN-ω underlie ∼40% of cases of WNV encephalitis.

Long-Term Outcomes in Children Surviving Tropical Arboviral Encephalitis: A Systematic Review

BACKGROUND

Survivors of childhood encephalitis often suffer from physical and neurocognitive sequelae, particularly in tropical, resource-limited areas with a large burden of arboviral, neurotropic pathogens and limited resources with which to address chronic morbidities. Research into overall and pathogen-specific outcomes following childhood encephalitis may help identify risk factors for poor outcomes, quantify the burden of sequelae, assist with resource allocation and help focus rehabilitative efforts. However, such research is limited. To this end, we systematically reviewed the literature on this topic to identify gaps in knowledge worthy of future investigation.

METHODS

A search of PubMed, Web of Knowledge and the Cochrane databases was performed 10 January through 20 February 2020, using 17 search terms for sequelae and 14 for tropical, arboviral pathogens. Eligible reports demonstrated post-discharge follow-up of ≥3 months and assessment of clinical outcome in a child with an arboviral encephalitis ≤18 years of age at diagnosis.

RESULTS

Of 1513 articles, 35 were eligible, comprising 693 children. Japanese encephalitis accounted for 18 articles and 93.2% of all subjects (646 total). Sequelae were documented in ∼60% of subjects overall and in those with Japanese encephalitis. For non-Japanese encephalitis virus encephalitides (47 children), sequelae were found in 78.1%. No studies utilized comprehensive neurocognitive testing or assessed the efficacy of rehabilitative efforts. Only nine studies reported data from ≥1 follow-up visit.

CONCLUSION

Investigation into long-term outcomes following tropical childhood encephalitis is limited, particularly for neurocognitive sequelae, serial assessments over time and the effect of rehabilitative measures.

LAY SUMMARY

Encephalitis, an infection of the brain, is frequently caused by arboviruses (viruses spread via the bite of infected arthropods, such as mosquitoes) in tropical locales. Following infection, surviving children may be plagued with severe physical and cognitive deficits. Unfortunately, research into the type of deficits, their frequency and their responsiveness to rehabilitative efforts is lacking. We identified and reviewed 35 studies describing outcomes in children recovering from tropical, arboviral encephalitis at least 3 months following hospital discharge. Poor outcomes were common and found in up to 60% of children. Long-term and serial follow-up visits were rare, as was the use of comprehensive neurocognitive testing. No studies assessed the efficacy of rehabilitative measures. Further study into these areas is recommended.

Evaluation for Arboviral Infection Among Children Hospitalized in Colorado With Aseptic Meningitis and Encephalitis

Among 39 children hospitalized in Colorado with aseptic meningitis or encephalitis, 16 (41%) had an etiology identified, including 2 (5%) with West Nile virus infection. Despite extensive testing, no other arboviral infections were identified. Arboviral infection should be considered in children with neuroinvasive disease during arboviral season with testing directed toward viruses endemic to the region and type of exposure.

Pediatric West Nile Virus-Associated Neuroinvasive Disease: A Review of the Literature

Over the past two decades, West Nile virus has become the most common arbovirus in North America, leading to several outbreaks and infecting thousands of people. Mosquitos help transmit the virus in the majority of cases, but transmission occurs via blood transfusions, organ transplantation, and possibly pregnancy and breastfeeding. While most infected patients experience mild to no symptoms, thousands of West Nile virus-associated neuroinvasive cases have been reported in the United States, with over 700 cases occurring in children from 2003 to 2016. Neuroinvasive disease presents as meningitis, encephalitis, or acute flaccid paralysis, and carries a high likelihood of poor outcome, including severe neurological disability or death. To date, no pharmacologic treatment has proven effective. Therapeutic clinical trials have not been successfully completed due to the sporadic nature of viral outbreaks and resultant poor study enrollment. Although older age and chronic disease are risk factors for neuroinvasive West Nile virus disease in adults, the specific factors that influence the risk in pediatric populations have not been fully elucidated. This review summarizes the most recent literature regarding West Nile virus-associated neuroinvasive disease, especially as it pertains to the pediatric population. Moreover, the review describes the epidemiology, clinical, laboratory, and radiographic findings, and outlines the various therapies that have been trialed and potential future research directions.