Name: west nile virus and brain infection
Uploaded: 2026-03-12T13:36:02.000Z
Duration: 1 min 25 s
Channel: JoVE

Arboviral encephalitis is an inflammation of the brain caused by arthropod-borne viruses, known as arboviruses.A common example is the West Nile virus, an enveloped positive-strand RNA virus, primarily transmitted by mosquitoes.When an infected mosquito bites, it injects the virus into the skin, where the virus enters dendritic cells through receptor-mediated endocytosis.It first replicates locally, then spreads to nearby lymph nodes, and later enters the bloodstream.Once in the blood, the virus can travel to various organs, including the brain.Here, the virus crosses the blood-brain barrier through several mechanisms.It may do so by directly infecting the endothelial cells, by disrupting the tight junctions, or by being transported via infected immune cells.After crossing the blood-brain barrier, the virus replicates inside neurons, triggering strong inflammation and the release of pro-inflammatory cytokines.The combined effects of viral cytotoxicity and immune responses lead to neuronal loss and inflammation in the brain, causing encephalitis.

arboviral encephalitis

Arboviral Encephalitis

Arboviral encephalitis refers to brain inflammation caused by arthropod-borne viruses, particularly those transmitted through mosquito vectors. Among these, West Nile virus (WNV), a member of the Flaviviridae family, is a significant public health concern. WNV is an enveloped, positive-sense, single-stranded RNA virus. Human infection typically begins when an infected mosquito introduces the virus into the dermis during feeding. The primary transmission cycle involves birds as amplifying hosts and mosquitoes as vectors, while humans and other mammals serve as incidental, dead-end hosts.Viral Entry and DisseminationAfter inoculation, WNV targets dendritic cells, entering through receptor-mediated endocytosis, and begins replicating at the site of entry. Initial viral replication occurs locally before the virus spreads to regional lymph nodes, where further amplification takes place. From the lymphatic system, WNV enters the bloodstream and spreads systemically to peripheral organs.Crossing the Blood-Brain BarrierA key step in the development of arboviral encephalitis is the virus&#8217;s ability to cross the blood-brain barrier (BBB), which normally protects the central nervous system (CNS) from pathogens. WNV can breach the BBB through several mechanisms. One route involves direct infection and compromise of endothelial cells, which leads to barrier dysfunction. Another mechanism is the disruption of tight junctions between endothelial cells, weakening the BBB&#8217;s structural integrity. A third method involves the "Trojan horse" strategy, where infected immune cells, such as monocytes or dendritic cells, transport the virus across the BBB.Effects on the Central Nervous SystemOnce inside the CNS, WNV shows a strong preference for neurons, particularly those in the cerebral cortex, brainstem, and spinal cord. Viral replication in neurons triggers immune responses, including the release of pro-inflammatory cytokines such as IL-6, TNF-&#945;, and interferons. This inflammatory environment, combined with direct viral damage, leads to neuronal death and clinical signs of encephalitis. The resulting neuroinflammation causes neurological symptoms that range from mild cognitive impairment to severe outcomes, such as seizures, paralysis, or coma, depending on the extent of CNS damage.Clinical ManifestationsMost WNV infections are either asymptomatic or present as a mild febrile illness. A small proportion of cases progress to neuroinvasive disease, especially among immunocompromised individuals or older adults.

Arboviral encephalitis refers to brain inflammation caused by arthropod-borne viruses, particularly those transmitted through mosquito vectors. Among ...

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west nile virus and brain infection

West Nile virus can cause brain inflammation when it reaches the central nervous system. This arboviral infection is spread by mosquitoes, especially in a cycle that involves birds as amplifying hosts and mosquitoes as vectors. Humans and other mammals are incidental dead-end hosts. Most human infections never become severe, but some progress to neuroinvasive disease.

West Nile virus, or WNV, is an enveloped, positive-sense, single-stranded RNA virus in the Flaviviridae family. Infection usually begins when an infected mosquito feeds and introduces the virus into the dermis. The virus then targets dendritic cells and enters them by receptor-mediated endocytosis. It first replicates locally at the entry site, then spreads to regional lymph nodes for more amplification.

After this early spread, WNV enters the bloodstream and moves throughout the body. A major step in encephalitis is crossing the blood-brain barrier, which normally protects the central nervous system from pathogens. The virus may do this by infecting and damaging endothelial cells, by disrupting tight junctions between those cells, or by using a “Trojan horse” route in which infected monocytes or dendritic cells carry it across.

Once inside the central nervous system, WNV prefers neurons in the cerebral cortex, brainstem, and spinal cord. Viral replication in neurons triggers inflammation, including the release of IL-6, TNF-α, and interferons. This immune response, along with direct viral injury, can kill neurons and lead to encephalitis.

The neurological effects can range from mild cognitive problems to severe outcomes such as seizures, paralysis, or coma. Most infections are asymptomatic or cause only a mild fever. Neuroinvasive disease is more likely in older adults and in people with weakened immune systems.

West Nile Virus and Brain Infection

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West Nile virus can cause brain inflammation when it reaches the central nervous system. This arboviral infection is spread by mosquitoes, especially in a cycle that involves birds as amplifying hosts and mosquitoes as vectors. Humans and other mammals are incidental dead-end hosts. Most human infections never become severe, but some progress to neuroinvasive disease. West Nile virus, or WNV, is an enveloped, positive-sense, single-stranded RNA virus in the Flaviviridae family. Infection...

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key terms and concepts

Explore how West Nile virus spreads by mosquitoes, crosses the blood-brain barrier, and can cause encephalitis in the brain and spinal cord.

West Nile Virus and Brain Infection | JoVE K12

JoVE Core Microbiology provides an engaging introduction to the microbial world and its influence on health, industry, and the environment. This comprehensive collection covers key concepts such as microbial structure, metabolism, genetics, and ecology. It introduces essential laboratory techniques and microscopy methods through visually engaging animations. Corresponding scientist-in-action videos bridge classroom concepts with real-world research and applications.

microbiology

West Nile Virus and Brain Infection

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