Dozens of viruses can infect or damage the peripheral nervous system, the vast network of nerves running from the spinal cord and brainstem out to the skin, muscles, and organs. Some, like herpes simplex and the varicella-zoster virus behind chickenpox, have evolved specifically to exploit peripheral nerves, setting up lifelong residence inside nerve cell clusters called ganglia. Others, like HIV and SARS-CoV-2, damage peripheral nerves as a side effect of broader infection. The consequences range from the burning pain of shingles to full limb paralysis, and the mechanisms behind each are strikingly different.
How Viruses Reach Peripheral Nerves
Viral infections typically begin outside the nervous system entirely, in the respiratory tract, the gut, a wound, or the bloodstream. From there, a virus can reach peripheral nerves through a few routes. The most studied is retrograde axonal transport: a virus enters the tip of a nerve fiber at a distant site, such as the skin or a muscle, and travels backward along the axon toward the nerve cell body. This is how herpes simplex virus reaches sensory ganglia after infecting skin cells, and how rabies travels from a bite wound to the spinal cord. A less dramatic but common route is hematogenous spread, where a virus circulating in the blood crosses into nerve tissue. Most viruses that end up in the nervous system are “opportunistic or accidental” invaders, meaning the nervous system is not their intended destination. Only a handful, most notably the alpha herpesviruses and rabies, have evolved to enter nerves efficiently and take advantage of the unique biology of neurons.1PubMed Central. Virus infections in the nervous system
What makes peripheral nerves particularly vulnerable is their anatomy. Their fibers can extend over a meter from the spinal cord to the fingertips or toes, offering a long unbroken highway for a virus that hitches a ride on the molecular motors that shuttle cargo along axons. And unlike the brain, which is partially shielded by the blood-brain barrier, peripheral nerves lack that protective wall, making them more accessible to both blood-borne pathogens and viruses that infect the tissues they innervate.
Herpes Simplex Virus and Lifelong Latency
Herpes simplex virus is one of the best-studied neurotropic viruses, and its signature trick is latency. After an initial infection of the skin or mucous membranes, the virus travels along sensory nerve fibers to the nearest ganglion, often the trigeminal ganglion for oral herpes or the sacral ganglia for genital herpes. Once there, it enters a dormant state inside neurons. During this latency, no infectious virus or viral proteins are detectable. The only molecular sign of the virus’s presence is a specific RNA transcript called the latency-associated transcript, or LAT.2Virology. Neuronal Control of Herpes Simplex Virus Latency
The host neuron plays an active role in keeping the virus quiet. Research on animal models has shown that when the nerve fiber connecting a ganglion to the periphery is severed, a process called neurectomy, the resulting disruption in normal neuronal activity leads to decreased LAT expression and even reduced viral DNA in the ganglion. In other words, the neuron’s own health and signaling patterns help maintain the virus in its latent state.2Virology. Neuronal Control of Herpes Simplex Virus Latency This relationship means that anything that stresses or injures the neuron, whether physical trauma, immune suppression, or even emotional stress, can tip the balance and allow the virus to reactivate, producing the painful sores people recognize as cold sores or genital herpes outbreaks.
Shingles and Postherpetic Neuralgia
Varicella-zoster virus follows a playbook similar to herpes simplex. After causing chickenpox in childhood, it retreats into sensory ganglia along the spine and skull and stays dormant, often for decades. When the immune system weakens from aging or immunosuppression, the virus can reactivate, producing the painful, blistering rash known as shingles. The rash typically follows the territory of a single nerve, appearing as a band across one side of the body, because it tracks the dermatome supplied by the ganglion where the virus was hiding.3PubMed Central. Herpes zoster (shingles) and postherpetic neuralgia
For many people, the rash heals within a few weeks. But in a substantial minority, the nerve damage left behind causes persistent burning, stabbing, or aching pain that lasts months or even years after the skin has cleared. This condition, postherpetic neuralgia, is defined as pain persisting more than three months after the rash has resolved, and it is notoriously difficult to treat.3PubMed Central. Herpes zoster (shingles) and postherpetic neuralgia The pain likely results from a combination of direct nerve fiber destruction during reactivation and a sustained inflammatory process in the ganglion that outlasts the active infection.
Rabies and Entry at the Neuromuscular Junction
Rabies takes a fundamentally different approach from the herpesviruses. Rather than targeting sensory nerves in the skin, rabies virus preferentially enters motor nerve endings at the neuromuscular junction, the point where a motor nerve fiber meets a muscle cell. Early experiments detected rabies virus antigen at sites matching the locations of motor end-plates within an hour of inoculation into mouse limbs, and the virus appeared in the motor neurons of the spinal cord’s ventral horn within twenty hours, well before it reached the sensory neurons in the dorsal root ganglia.4PubMed. Entry of rabies virus into the peripheral nerves of mice
The virus exploits receptors concentrated at the neuromuscular junction. Nicotinic acetylcholine receptors, the same receptors that allow nerves to signal muscles to contract, appear to help the virus bind and gain entry. In nerve-muscle coculture experiments, fluorescent markers that bind to these receptors colocalized precisely with rabies virus at the junction, confirming it as the primary entry point. Once internalized at the motor terminal, the virus travels by retrograde transport toward the spinal cord and eventually the brain.5PubMed. Rabies virus entry at the neuromuscular junction in nerve-muscle cocultures6PubMed Central. The acetylcholine receptor as a cellular receptor for rabies virus This route explains the long and variable incubation period of rabies: the virus must physically travel from the bite site to the central nervous system, and bites farther from the brain take longer to produce symptoms.
Enteroviruses and Motor Neuron Destruction
Poliovirus was the most feared virus known to destroy peripheral motor neurons, but it has largely been eliminated by vaccination. Its modern cousin, enterovirus D68, emerged in 2014 as a cause of acute flaccid myelitis, a condition in which children develop sudden, severe limb weakness or paralysis. The mechanism is grimly similar to polio: the virus reaches the anterior horn cells of the spinal cord, the motor neurons whose axons extend out through peripheral nerves to control muscles, and kills them.7PubMed Central. Acute flaccid myelitis and enterovirus D68: lessons from the past and present
Mouse model studies have shown that intramuscular injection of certain enterovirus D68 strains causes infection of the spinal cord, death of motor neurons, and progressive paralysis that closely resembles the human disease. A specific viral structural protein, VP1, was identified as the primary factor determining whether a given strain could grow in the spinal cord and destroy motor neurons.8PubMed Central. VP1 is the primary determinant of neuropathogenesis in a mouse model of enterovirus D68 acute flaccid myelitis Because the anterior horn cells sit at the junction between the central and peripheral nervous systems, their destruction by enteroviruses produces what is functionally a peripheral nerve disease: the muscles downstream of the lost neurons become paralyzed and may atrophy permanently.
West Nile Virus and Bidirectional Axonal Spread
West Nile virus, a mosquito-borne flavivirus, adds a twist to the picture. Using compartmentalized neuron cultures that allow researchers to expose just one end of a nerve cell to the virus while monitoring the other, studies demonstrated that West Nile virus can spread in both directions along an axon, not only from the nerve terminal toward the cell body (retrograde) but also from the cell body outward toward the terminals (anterograde). This bidirectional spread helps explain how the virus moves from peripheral tissues into the central nervous system and causes the acute limb paralysis seen in some severe infections.9PubMed Central. Axonal transport mediates West Nile virus entry into the central nervous system and induces acute flaccid paralysis
Most people who contract West Nile virus have no symptoms or experience a mild fever. But in roughly one out of every 150 infections, the virus breaches the nervous system. The resulting paralysis, like that caused by enteroviruses, stems from damage to motor neurons and can be permanent. The bidirectional transport mechanism also raises the possibility that once in the spinal cord, the virus could spread outward to other peripheral nerve branches, potentially widening the scope of neurological damage.
Guillain-Barré Syndrome and Molecular Mimicry
Not all viral damage to peripheral nerves comes from the virus itself. In Guillain-Barré syndrome, the immune system attacks peripheral nerves after a preceding infection, and the trigger is a case of mistaken identity. Certain bacterial and viral pathogens carry surface molecules that resemble gangliosides, a class of fat-based molecules concentrated in the membranes of peripheral nerves. The immune system generates antibodies against the pathogen, and those antibodies cross-react with the nerve’s own gangliosides, leading to nerve inflammation and demyelination.10PubMed Central. Guillain-Barré syndrome: expanding the concept of molecular mimicry
At least five distinct bacterial and viral pathogens are known to trigger Guillain-Barré syndrome. Among the viral triggers, cytomegalovirus is the most common antecedent. Patients who develop the syndrome after CMV infection tend to have particularly severe sensory deficits and produce antibodies against a specific ganglioside, GM2. Laboratory studies have shown that CMV-infected cells express the GM2 molecule on their surfaces, giving the immune system a molecular look-alike to target.11PubMed. Infectious origins of, and molecular mimicry in, Guillain-Barré and Fisher syndromes The result is an ascending paralysis that typically begins in the legs and moves upward, and in severe cases can affect the muscles used for breathing. Most people recover, but the process can take weeks to months, and some are left with lasting weakness.
HIV-Associated Peripheral Neuropathy
HIV attacks the immune system, but peripheral neuropathy is one of its most common neurological complications and a major source of chronic suffering. The sensory neuropathies linked to HIV are widespread among people with advanced infection, causing burning pain, tingling, and numbness that typically start in the feet and progress upward. To make matters more frustrating, some of the antiretroviral drugs used to treat HIV can themselves damage peripheral nerves, making it difficult to separate the effects of the virus from those of its treatment.12The Lancet Neurology. Neurological complications of HIV infection
The virus appears to harm nerves through multiple pathways. HIV’s envelope protein, gp120, has been shown to directly activate pain-sensing neurons and small nerve fibers. Meanwhile, the class of antiretroviral drugs called nucleoside reverse transcriptase inhibitors can cause mitochondrial dysfunction in nerve cells, leading to energy failure and nerve fiber death. The clinical picture for the patient is the same, burning feet and shooting pain, but the underlying cause may be viral, drug-related, or both simultaneously, complicating treatment decisions.
Cranial Nerves as Viral Highways
The cranial nerves, the twelve pairs of nerves that emerge directly from the brain and brainstem rather than the spinal cord, are a particularly interesting target for neurotropic viruses. The olfactory nerve, which carries smell signals from the nose to the brain, has long been recognized as a route for viruses to bypass the blood-brain barrier. But recent research has drawn attention to the trigeminal nerve, the large sensory nerve supplying the face, as an underappreciated pathway.
In mouse models of SARS-CoV-2 infection, the trigeminal ganglion turned out to be an early and highly efficient site of viral replication following intranasal inoculation. The virus replicated there rapidly and then spread throughout the brain, primarily targeting neurons. This suggests the trigeminal nerve acts as a complementary route to the olfactory nerve for SARS-CoV-2 to reach the brain, producing its own distinct pattern of damage.13UTMB Shared Electronic Theses and Dissertations. The Road Less Taken: Characterizing the Trigeminal Nerve Route of Neuroinvasion by Respiratory SARS-CoV-2 Clinically, cases of trigeminal neuropathy presenting after SARS-CoV-2 infection have been documented, with facial numbness and pain in trigeminal distributions that developed during or shortly after COVID-19.14PubMed Central. Trigeminal neuropathy presenting secondary to SARS-CoV-2 infection
Herpes simplex virus type 1 also uses cranial nerve pathways. Studies tracking the spread of HSV-1 during primary infection found that after infecting the nasal lining, the virus spread through the olfactory nerve and trigeminal ganglion connections into specific brainstem regions, as well as other cranial nerve nuclei including those of the vagus and hypoglossal nerves.15PubMed Central. Olfactory and trigeminal routes of HSV-1 CNS infection with regional microglial heterogeneity The fact that multiple unrelated viruses converge on the same cranial nerve routes speaks to how accessible these pathways are.
Small Fiber Neuropathy After Viral Infections
A pattern that has gained attention since the COVID-19 pandemic is small fiber neuropathy, the selective damage to the thinnest nerve fibers that carry pain and temperature signals and regulate automatic body functions like heart rate and sweating. In a study of patients with confirmed SARS-CoV-2 infection who developed neuropathy symptoms, skin biopsy confirmed small fiber neuropathy in nearly half of those tested. Some also showed autonomic dysfunction.16PubMed Central. Small fiber neuropathy associated with SARS-CoV-2 infection
The damage did not always correlate with how severe the original COVID-19 illness had been: patients with markedly reduced nerve fiber density included those who had experienced severe illness and those who had not. Research comparing post-COVID patients with those who have chronic fatigue syndrome found strikingly similar patterns, including inappropriate resting tachycardia, a high frequency of postural tachycardia syndrome, and damage preferentially affecting unmyelinated fibers. The distribution of nerve fiber loss was often non-length-dependent, meaning it did not follow the typical “stocking-glove” pattern that starts at the feet, suggesting a process distinct from the most common forms of neuropathy seen in conditions like diabetes.17PubMed Central. Dysautonomia and small fiber neuropathy in post-COVID condition and Chronic Fatigue Syndrome
SARS-CoV-2 is not the only virus linked to small fiber neuropathy. Hepatitis C, particularly when it triggers a condition called cryoglobulinemia in which abnormal antibody proteins circulate in the blood, has long been associated with peripheral neuropathy involving both small and large fibers.18PubMed. Clinical, neurophysiological, and skin biopsy findings in peripheral neuropathy associated with hepatitis C virus-related cryoglobulinemia
What Happens Inside an Infected Ganglion
When a virus infects a peripheral ganglion, the local immune response is fierce and complex. Detailed profiling of human dorsal root ganglia infected with varicella-zoster virus revealed dramatic upregulation of inflammatory signaling molecules. Interferon-alpha, interferon-gamma, and the interferon-induced signaling molecule IP10 increased substantially, with IP10 rising twenty-fold over baseline. Pro-inflammatory cytokines including IL-1-alpha, IL-6, and IL-8 surged as well, with IL-8 rising more than sixteen-fold. These molecules recruit immune cells and sensitize pain-sensing neurons, which helps explain why shingles and other ganglion infections produce such intense pain.19PLoS Pathogens. Neuronal Subtype and Satellite Cell Tropism Are Determinants of Varicella-Zoster Virus Virulence in Human Dorsal Root Ganglia Xenografts In Vivo
The ganglia also mounted an anti-inflammatory counterresponse: TGF-beta, a powerful regulatory molecule, rose about four-fold, suggesting the ganglion tries to limit collateral damage even as it fights the infection. This tug-of-war between pro-inflammatory pain signals and anti-inflammatory braking mechanisms likely determines how much nerve damage persists once the virus is cleared and whether a patient goes on to develop chronic neuropathic pain.
The inflammatory profile also matters because these same signaling molecules, TNF, IL-1-beta, and others, can directly sensitize pain-sensing nerve fibers (nociceptors) to produce pain even without ongoing nerve destruction. Studies of severe COVID-19 found that immune cells in the blood showed transcriptional upregulation of signaling molecules known to act on receptors in human dorsal root ganglia, suggesting a mechanism by which systemic viral infection can generate pain through the peripheral nervous system even without the virus directly infecting neurons.20PubMed Central. Neurobiology of SARS-CoV-2 interactions with the peripheral nervous system: implications for COVID-19 and pain
Diagnosing Viral Peripheral Neuropathies
Figuring out whether a peripheral neuropathy has a viral cause can be challenging, because the symptoms, numbness, tingling, burning pain, weakness, overlap with dozens of non-viral neuropathies like those from diabetes, alcohol use, or autoimmune disease. Diagnosis usually involves a combination of clinical history, nerve conduction studies, and sometimes skin biopsy.
Nerve conduction studies measure the speed and strength of electrical signals traveling through larger nerve fibers, which picks up damage to myelinated fibers well. But they are essentially blind to small fiber neuropathy because the thinnest unmyelinated fibers do not contribute to the signals being measured. For small fiber involvement, skin punch biopsy is the gold standard: a tiny sample of skin is examined under a microscope, and the density of nerve fibers penetrating the outer skin layer is counted. A low count confirms small fiber loss.16PubMed Central. Small fiber neuropathy associated with SARS-CoV-2 infection Autonomic function testing can also reveal damage to the nerve fibers that control sweating, heart rate, and blood pressure.
Linking the neuropathy to a specific virus requires additional evidence: a recent documented infection, characteristic patterns of involvement (for example, a dermatomal distribution strongly suggests varicella-zoster), the timing of symptom onset relative to the infection, and sometimes viral PCR or antibody testing of blood or cerebrospinal fluid. In the case of Guillain-Barré syndrome, characteristic findings on nerve conduction studies combined with elevated protein in the cerebrospinal fluid and a history of recent infection often clinch the diagnosis.
Vaccines That Protect Peripheral Nerves
The most direct way to prevent viral peripheral nerve damage is vaccination. The recombinant zoster vaccine, Shingrix, is the clearest example of a vaccine designed with peripheral nerve protection as a primary goal. Unlike the older live-virus vaccine, the recombinant version uses a single viral protein combined with an adjuvant to generate strong immunity even in older adults whose immune systems are waning.21PubMed Central. Recombinant zoster vaccine (Shingrix®): a new option for the prevention of herpes zoster and postherpetic neuralgia
The real-world numbers are striking. Full vaccination with the recombinant zoster vaccine showed about 87% effectiveness against postherpetic neuralgia, the chronic nerve pain that makes shingles most feared. Even in people who got shingles despite vaccination, the risk of going on to develop postherpetic neuralgia dropped by roughly half compared to unvaccinated individuals. Protection remained strong over time, with effectiveness against postherpetic neuralgia at about 90% through the first two years, settling to around 77% beyond the second year.22JAMA Network Open. Recombinant Zoster Vaccination and Risk of Postherpetic Neuralgia or Zoster Ophthalmicus For herpes zoster affecting the eye, a particularly dangerous complication because the virus reactivates in the trigeminal ganglion’s ophthalmic branch, full vaccination was about 78% effective.22JAMA Network Open. Recombinant Zoster Vaccination and Risk of Postherpetic Neuralgia or Zoster Ophthalmicus
People taking corticosteroids, a common immunosuppressive scenario, still benefited substantially from vaccination, though their protection against postherpetic neuralgia was somewhat lower, about 75% versus 88% in those not on corticosteroids. Both the older live-virus vaccine and the newer recombinant vaccine have been studied in immunocompetent adults and in selected immunocompromised populations, with the recombinant vaccine consistently proving more effective.23PubMed Central. Herpes Zoster Vaccines
Viral Vectors Repurposed for Nerve Repair
In a twist that borders on ironic, the same properties that make viruses dangerous to peripheral nerves, their ability to enter nerve cells, travel along axons, and deliver genetic material, have made modified viruses attractive tools for gene therapy aimed at nerve repair. Adeno-associated viral vectors, which are based on a small, harmless virus, are the most widely used platform. The first approved AAV-based therapy reached the European market over a decade ago, and the approach has since expanded to dozens of clinical programs. Researchers are now exploring whether AAV vectors can be used to deliver growth factors and other genes directly to injured peripheral nerves to promote regeneration after trauma.24PubMed Central. Gene therapy and peripheral nerve repair: a perspective
The peripheral nervous system has an inherent capacity for regeneration that the central nervous system lacks, but recovery after severe nerve injuries is often slow and incomplete. Delivering neurotrophic factors or anti-inflammatory genes via viral vectors directly to the injury site could accelerate the process. Most of this work remains in animal models, but the translation from laboratory to clinic is well underway for CNS applications, and peripheral nerve repair is beginning to attract similar investment. It is a strange circle: viruses that once caused devastating nerve diseases may ultimately help heal them.