Risk factors for neurological complications in children with Flavivirus infection

This study aims to characterize the acute neurological manifestations caused by DENV, ZIKV, and YFV during hospitalization; identify the risk factors associated with persistent neurological complications after discharge; and evaluate the time to resolution during clinical follow-up. A prospective study evaluated 505 children, between March 2014 and July 2019, hospitalized with neurological manifestations and that doctors suspected infection of the central nervous system (CNS). Viral infection of collected cerebrospinal fluid (CSF) was confirmed by real-time reverse transcription-polymerase chain reaction (RT-PCR). Patients were clinically followed up after hospital discharge. Analysis of predictive factors and survival curves was performed. This study identified clinical symptoms and changes in the CSF laboratory, electroencephalogram (EEG), and CNS image as predictors of complications in children with confirmed infection in the CNS by DENV, ZIKV, or YFV. No statistical difference was found (p value 0.574) in the time to the resolution of complications in children after hospital discharge between the three types of flaviviruses. Children with YFV, detected in CSF samples, had a 53% higher risk of developing neurological complications. Performing etiological diagnosis by RT-PCR of CSF samples of children with neurological manifestations, especially during Flavivirus outbreaks, is an essential tool for improving the prognosis and clinical follow-up of these patients.

Human Usutu Virus Infection with Atypical Neurologic Presentation, Montpellier, France, 2016

Infection with Usutu virus (USUV) has been recently associated with neurologic disorders, such as encephalitis or meningoencephalitis, in humans. These findings indicate that USUV is a potential health threat. We report an acute human infection with USUV in France putatively associated with a clinical diagnosis of idiopathic facial paralysis.

First human case of Usutu virus neuroinvasive infection, Italy, August-September 2009

We report the first worldwide case of Usutu virus (USUV) neuroinvasive infection in a patient with diffuse large B cell lymphoma who presented with fever and neurological symptoms and was diagnosed with meningoencephalitits. The cerebrospinal fluid was positive for USUV, and USUV was also demonstrated in serum and plasma samples by RT-PCR and sequencing. Partial sequences of the premembrane and NS5 regions of the viral genome were similar to the USUV Vienna and Budapest isolates.

Hippocampal involvement in dengue fever

Flaviviruses are among the most important emerging viruses known to man. Dengue is the most common flavivirus infection in Singapore, and is transmitted between humans by the Aedes mosquito. We report a 25-year-old man with dengue fever complicated by selective hippocampal involvement manifesting as amnesia. This has not been described in the literature previously. Dengue polymerase chain reaction and serology were positive. Magnetic resonance imaging of the brain showed bilateral hippocampal involvement.

Flaviviruses in motor neuron disease

Sporadic motor neuron disease (MND) causes a progressive loss of motor neurons. West Nile virus can attack motor neurons, so we examined whether flavivirus infection could be detected in MND cases. Spinal cord sections from 22 MND cases were stained immunohistochemically with a flavivirus-specific antibody. No staining for flavivirus was seen in any case. Sporadic MND does not appear to arise from a recent infection with a flavivirus.

Alteration of clinical outcome and histopathology of yellow fever virus infection in a hamster model by previous infection with heterologous flaviviruses

Using a recently described hamster model of severe yellow fever (YF), we examined the hypothesis that prior infection with heterologous flaviviruses protects against severe or fatal YF. Hamsters were singly or sequentially infected with Japanese encephalitis, St. Louis encephalitis, West Nile, and/or dengue-1 viruses, and then challenged with a virulent strain of yellow fever virus (YFV). In contrast to control (naive) hamsters, many of which appeared clinically ill or died after YFV infection, the flavivirus-immune animals remained asymptomatic. The flavivirus-immune hamsters also had a reduced viremia and lower serum levels of alanine aminotransferase and total bilirubin, compared with naive hamsters, following YFV infection. Histologically, livers of animals in the flavivirus-immune and control groups showed comparable levels of multifocal necrapoptosis. However, steatosis was not observed in the flavivirus-immune animals, whereas naive hamsters developed extensive microvesicular steatosis in the liver following YFV infection. These findings suggest that hepatocytic steatosis is an adverse microscopic feature associated with severe disease in YFV infection. Our experimental results support earlier anecdotal reports that prior exposure of humans to heterologous flaviviruses reduces subsequent risk of fatal YFV infection.

Dengue infection presenting with central nervous system manifestation

The objective of this study was to investigate the possibility of dengue virus infection causing an abnormal neurologic presentation. Between 1996 and 1998, all pediatric patients with clinical manifestations of encephalitis-like illness who were admitted to the Department of Pediatrics, Siriraj Hospital were prospectively studied for any evidence of dengue virus infection. The diagnosis of dengue virus infection was based on mosquito viral isolation and serologic and polymerase chain reaction (PCR) evidence. Of 44 patients with the preliminary diagnosis of acute viral encephalitis, 8 were diagnosed with dengue infection. All of these 8 patients were diagnosed by serology. In addition to the serologic diagnosis, four also had positive PCR, one had positive viral isolation, and one had both positive PCR and viral isolation. Only two patients were diagnosed by serologic evidence alone. All except one had clinical courses and laboratory findings compatible with typical dengue infection. All had obvious encephalitic clinical manifestations with normal cerebrospinal fluid findings except one patient, who had mildly increased cerebrospinal fluid protein. All of these patients recovered completely and had benign clinical courses except one patient, who developed leakage symptoms. None had liver failure. Dengue virus can cause acute encephalopathy with fever. It can masquerade as other types of acute viral encephalitis. However, its clinical course and prognosis are usually favorable.