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# Viral (aseptic) meningitis

Viral meningitis is an infection of the membranes around the brain and [spinal cord](https://durgical.com/en/anatomy/spinal-cord/) caused by a virus. It is usually milder than bacterial meningitis.

Updated 2026-11-01

## Structures involved

Tap one to see what it is and open it in 3D.

- [Dura mater](https://durgical.com/en/anatomy/cranial-dura/)
- [Spinal cord](https://durgical.com/en/anatomy/spinal-cord/)
- [Lateral ventricles](https://durgical.com/en/anatomy/lateral-ventricle/)
- [Choroid plexus](https://durgical.com/en/anatomy/choroid-plexus/)

## Why it happens

- [CSF and the blood–brain barrier](https://durgical.com/en/physiology/csf-and-the-blood-brain-barrier/)
- [Blood–brain barrier, choroid plexus and cerebrospinal fluid](https://durgical.com/en/histology/blood-brain-barrier-choroid-plexus-and-cerebrospinal-fluid/)
- [Gray and white matter, cerebellar cortex, meninges](https://durgical.com/en/histology/gray-and-white-matter-cerebellar-cortex-meninges/)

## What it is

Inflammation of the leptomeninges (arachnoid and pia mater) caused by a virus, with fever, headache and neck stiffness but preserved consciousness. It is the most common form of meningitis and is called aseptic because routine bacterial cultures are negative.

## Who gets it

Occurs worldwide at all ages, most often in children and young adults. Enteroviral cases rise in warm months in temperate countries and can occur year-round in the tropics, including Colombia. Outbreaks of enteroviral meningitis occur in schools and communities. Mumps meningitis has fallen where vaccination coverage is high.

## Causes

- Non-polio enteroviruses (echoviruses, coxsackieviruses), the most common cause
- Herpes simplex virus, especially type 2, which can cause recurrent episodes (Mollaret meningitis)
- Varicella-zoster virus and, less often, Epstein-Barr virus
- Arboviruses (for example West Nile virus) and acute HIV infection
- Mumps, measles and lymphocytic choriomeningitis virus (rodent exposure)

## Risk factors

- Young children and infants, who become more severely ill
- Contact with an infected person or crowded settings during outbreaks
- Recent primary genital herpes
- Weakened immunity (HIV, chemotherapy, transplant)
- Lack of vaccination against mumps, measles and varicella

## Pathophysiology

Most viruses reach the meninges through the blood after replicating in the gut or respiratory tract; herpesviruses may also travel along nerves. Infection of the meninges triggers inflammation in the subarachnoid space with a lymphocyte-predominant cellular response. Unlike bacterial meningitis, the brain tissue itself is usually spared, so consciousness and focal function are preserved; involvement of brain tissue defines meningoencephalitis.

## Symptoms and signs

- Fever and headache, often frontal or behind the eyes
- Neck stiffness and pain on bending the head forward
- Photophobia, nausea and vomiting
- Malaise and myalgia; rash, diarrhoea or mouth ulcers with enteroviruses
- Irritability, poor feeding and fever without clear focus in infants

## Red flags

- Confusion, drowsiness, seizures or focal neurological signs (suggest encephalitis or bacterial meningitis)
- A petechial or purpuric rash (possible meningococcal disease)
- Rapidly worsening illness, very high fever or shock
- Any febrile infant under three months, or an immunocompromised person
- Symptoms after recent antibiotic use, which can mask bacterial meningitis

## Diagnosis

**Clinical**
Fever, headache and meningism in a person with normal consciousness. Clinical features alone cannot exclude bacterial meningitis, so lumbar puncture is central unless contraindicated.

**Tests**
Cerebrospinal fluid typically shows a modest pleocytosis with lymphocytes (neutrophils may predominate very early), normal or mildly raised protein and normal glucose, with a negative Gram stain and culture. PCR of CSF identifies enteroviruses, herpes simplex and varicella-zoster virus. Blood cultures, HIV testing and serology are added according to exposure.

**Imaging**
CT or MRI of the head is done before lumbar puncture only when there are signs of raised pressure, focal deficits, seizures, reduced consciousness or immunosuppression; MRI helps when encephalitis is suspected.

## Differential diagnosis

- Bacterial meningitis (neutrophils, low CSF glucose, high protein)
- Herpes simplex encephalitis (confusion, seizures, [temporal lobe](https://durgical.com/en/anatomy/middle-temporal-gyrus/) changes)
- Tuberculous or cryptococcal meningitis (subacute, low glucose, high protein)
- Partially treated bacterial meningitis
- Subarachnoid haemorrhage (sudden thunderclap headache)
- Drug-induced aseptic meningitis (NSAIDs, intravenous immunoglobulin) or meningitis from autoimmune disease

## Goal of treatment

Exclude or cover bacterial and herpetic causes quickly, relieve symptoms and support hydration while the infection resolves.

## Treatment

**Conservative**
Rest, fluids, analgesics and antiemetics; a quiet, dim room helps with photophobia.

**Medical**
Empirical antibiotics are given until bacterial meningitis is excluded when the CSF is not clearly viral or the person is unwell. Acyclovir is used for herpes simplex or varicella-zoster meningitis, and antiretroviral therapy when acute HIV is the cause; enteroviral meningitis has no specific antiviral.

**Follow-up**
Neurological observation for changes in consciousness, seizures or new deficits; hydration and sodium in children; review of CSF culture and PCR results.

## Complications

- Encephalitis (meningoencephalitis)
- Dehydration and, rarely, hyponatraemia
- Prolonged headache, fatigue or difficulty concentrating for weeks
- Severe systemic enteroviral disease in newborns (myocarditis, hepatitis)
- Recurrent episodes with herpes simplex type 2

## Prognosis

Usually good in children over one year and adults, with recovery in about one to two weeks and no lasting deficit. Newborns and immunocompromised people can have severe disease.

## Prevention

- Handwashing, especially after changing diapers, and cleaning shared surfaces
- Vaccination against mumps, measles, varicella and influenza
- Avoiding mosquito bites and contact with wild rodents

## Test yourself

Think of the answer, then tap the question to see it.

## What is the most common cause of viral meningitis?

Non-polio enteroviruses (echoviruses and coxsackieviruses).

## What are the typical CSF findings in viral meningitis?

Lymphocytic pleocytosis, normal or mildly raised protein, normal glucose and a negative Gram stain.

## Which virus causes recurrent benign lymphocytic (Mollaret) meningitis?

Herpes simplex virus, mainly type 2.

## Which clinical feature points away from simple viral meningitis toward encephalitis?

Altered consciousness, seizures or focal neurological deficits, which show brain tissue involvement.

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## Related conditions

- [Bacterial meningitis](https://durgical.com/en/conditions/bacterial-meningitis/)
- [Viral encephalitis (herpes simplex encephalitis)](https://durgical.com/en/conditions/viral-encephalitis/)
- [Genital herpes (herpes simplex infection)](https://durgical.com/en/conditions/genital-herpes/)
- [Mumps](https://durgical.com/en/conditions/mumps/)
- [HIV infection and AIDS](https://durgical.com/en/conditions/hiv-infection-and-aids/)
- [Cryptococcal meningitis](https://durgical.com/en/conditions/cryptococcal-meningitis/)
- [Hand, foot and mouth disease](https://durgical.com/en/conditions/hand-foot-and-mouth-disease/)
- [Subarachnoid haemorrhage](https://durgical.com/en/conditions/subarachnoid-haemorrhage/)
- [Migraine](https://durgical.com/en/conditions/migraine/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [About Viral Meningitis | Meningitis | CDC](https://www.cdc.gov/meningitis/about/viral-meningitis.html) (Centers for Disease Control and Prevention, 2025); [Meningitis: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000680.htm) (MedlinePlus (U.S. National Library of Medicine), 2024).

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Source: https://durgical.com/en/conditions/viral-meningitis/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/viral-meningitis/