Dengue, zika, and chikungunya are arboviruses of great epidemiological relevance worldwide. The emergence and re-emergence of viral infections transmitted by mosquitoes constitute a serious human public health problem. The neurological manifestations caused by these viruses have a high potential for death or sequelae. The complications that occur in the nervous system associated with arboviruses can be a challenge for diagnosis and treatment. In endemic areas, suspected cases should include acute encephalitis, myelitis, encephalomyelitis, polyradiculoneuritis, and/or other syndromes of the central or peripheral nervous system, in the absence of a known explanation. The confirmation diagnosis is based on viral (isolation or RT-PCR) or antigens detection in tissues, blood, cerebrospinal fluid, or other body fluids, increase in IgG antibody titers between paired serum samples, specific IgM antibody in cerebrospinal fluid and serological conversion to IgM between paired serum samples (non-reactive in the acute phase and reactive in the convalescent). The cerebrospinal fluid examination can demonstrate: 1. etiological agent; 2. inflammatory reaction or protein-cytological dissociation depending on the neurological condition; 3. specific IgM, 4. intrathecal synthesis of specific IgG (dengue and chikungunya); 5. exclusion of other infectious agents. The treatment of neurological complications aims to improve the symptoms, while the vaccine represents the great hope for the control and prevention of neuroinvasive arboviruses. This narrative review summarizes the updated epidemiology, general features, neuropathogenesis, and neurological manifestations associated with dengue, zika, and chikungunya infection.

Objective To detect the frequency of dengue virus (DENV), Chikungunya virus (CHIKV), and Zika virus (ZIKV) in adult patients with suspected viral infection of the CNS or postinfectious syndromes living in the state of Rio de Janeiro, Brazil. Methods DENV, CHIKV, and ZIKV RNA by reverse transcription PCR (RT-PCR) and specific IgM antibodies were investigated in 47 CSF and serum samples of 36 adult patients suspected with viral infection or postinfectious neurologic diseases. In addition, intrathecal synthesis of anti-DENV and anti-CHIKV IgG antibodies was also evaluated using a specific antibody index. Results Of the total group, neuroinvasive arbovirus was confirmed in 31% (11/36) of the cases: 6 (55%) by RT-PCR in CSF and/or serum, 1 (9%) by RT-PCR in CSF and/or serum and specific IgM in CSF, and 4 (36%) by specific IgM in CSF. Five cases had DENV infection, and 6 patients were positive for CHIKV. No sample amplified for ZIKV. In addition, 3 of 7 (42%) tested cases had intrathecal synthesis of DENV or CHIKV antibodies. The neurologic complications included encephalitis (7), Guillain-Barré syndrome (2), optic neuritis (1), neuromyelitis optica spectrum disorder (1), polyneuropathy, (1) and myelitis (1). Conclusion DENV and CHIKV are a frequent cause of emerging and reemerging infections. It increases the number of cases with neurologic complications worldwide. We demonstrated that the combined use of molecular and immunologic tests in CSF/serum might support more widely the diagnosis of neurologic disorders caused by arbovirus in endemic areas. The detection of intrathecal synthesis of specific IgG antibodies may be promising for the retrospective diagnosis of neuroinvasive disorders caused by arbovirus.

Recent reports indicate that besides respiratory and systemic symptoms among coronavirus disease (COVID-19) patients, the disease has a wide spectrum of neurological manifestations (encephalitis, meningitis, myelitis, acute disseminated encephalomyelitis, metabolic and acute hemorrhagic necrotizing encephalopathy, cerebrovascular diseases, Guillain-Barré syndrome, polyneuritis cranialis, dysautonomia, and myopathies). The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can spread from the respiratory system to the central nervous system, using transneuronal and hematogenous mechanisms. Although not every COVID-19 patient will test positive for the virus in the cerebrospinal fluid exam, the appearance of neurological symptoms associated with SARS-CoV-2 infection reveals the importance of understanding the neurologic manifestations and capacity for neural invasion associated with the pathogen. These aspects are relevant for correct diagnosis and treatment, and for the potential development of vaccines. This review highlights the latest evidence of SARS-CoV-2 infection with a focus on neurological involvement and potential neuropathogenesis mechanisms.

Dengue, Zika and Chikungunya are emerging arboviruses and important causes of acute febrile disease in tropical areas. Although dengue does not represent a new condition, a geographic expansion over time has occurred with the appearance of severe neurological complications. Neglect has allowed the propagation of the vector (Aedes spp), which is also responsible for the transmission of other infections such as Zika and Chikungunya throughout the world. The increased number of infected individuals has contributed to the rise of neurological manifestations including encephalitis, myelitis, meningitis, Guillain-Barré syndrome and congenital malformations such as microcephaly. In this narrative review, we characterize the impact of the geographic expansion of the vector on the appearance of neurological complications, and highlight the lack of highly accurate laboratory tests for nervous system infections. This represents a challenge for public health in the world, considering the high number of travelers and people living in endemic areas.