Editing Viral meningitis

{{Infobox medical condition (new)
| name            = Viral meningitis
| synonyms        = Aseptic meningitis
| image           = Meninges-en.svg
| caption         = Viral meningitis causes inflammation of the meninges.
| field           = [[Neurology]]
}}

<!-- Definition and symptoms -->
'''Viral meningitis''', also known as '''aseptic meningitis''', is a type of [[meningitis]] due to a [[viral infection]]. It results in [[inflammation]] of the [[meninges]] (the membranes covering the brain and [[spinal cord]]). Symptoms commonly include [[headache]], [[fever]], [[photophobia|sensitivity to light]] and [[neck stiffness]].<ref name="Viral meningitis">{{cite journal | vauthors = Logan SA, MacMahon E | title = Viral meningitis | journal = BMJ | volume = 336 | issue = 7634 | pages = 36–40 | date = January 2008 | pmid = 18174598 | pmc = 2174764 | doi = 10.1136/bmj.39409.673657.ae }}</ref> 

<!-- Causes and diagnosis -->
Viruses are the most common cause of [[aseptic meningitis]].{{medical citation needed|date=July 2023}} Most cases of viral meningitis are caused by [[enteroviruses]] (common stomach viruses).<ref>{{cite web|title=Epidemiology|url=http://dhss.alaska.gov/|website=Alaska Department of Health and Social Services}}</ref><ref name="Viral meningitis"/><ref>{{cite journal | vauthors = Ratzan KR | title = Viral meningitis | journal = The Medical Clinics of North America | volume = 69 | issue = 2 | pages = 399–413 | date = March 1985 | pmid = 3990441 | doi = 10.1016/s0025-7125(16)31051-3 }}</ref> However, other viruses can also cause viral meningitis, such as [[West Nile virus]], [[Mumps virus|mumps]], [[Measles virus|measles]], [[Herpes simplex virus|herpes simplex]] types I and II, [[Varicella zoster virus|varicella]] and [[lymphocytic choriomeningitis]] (LCM) virus.<ref name="Viral meningitis" /><ref>{{cite web|url=http://www.publichealth.lacounty.gov/acd/procs/b73/DiseaseChapters/B73MeningitisViral.pdf|title=Meningitis, Viral|date=March 2015|website=lacounty.gov|series=Acute Communicable Disease Control Manual|publisher=County of Los Angeles Dept. of Public Health|access-date=January 2, 2019}}</ref> Based on clinical symptoms, viral meningitis cannot be reliably differentiated from [[bacterial meningitis]], although viral meningitis typically follows a more benign clinical course. Viral meningitis has no evidence of bacteria present in [[cerebral spinal fluid]] (CSF). Therefore, [[lumbar puncture]] with CSF analysis is often needed to identify the disease.<ref name=CDC2017 />

<!-- Treatment -->
In most cases, there is no specific treatment, with efforts generally aimed at relieving symptoms (headache, fever or nausea).<ref>{{Cite web|url=http://www.meningitis.org/disease-info/types-causes/viral-meningitis|title=Viral Meningitis - Meningitis Research Foundation|website=www.meningitis.org|access-date=2017-03-02|archive-date=2017-03-03|archive-url=https://web.archive.org/web/20170303123325/http://www.meningitis.org/disease-info/types-causes/viral-meningitis|url-status=dead}}</ref> A few viral causes, such as [[Herpes simplex virus|HSV]], have specific treatments.

<!-- Epidemiology -->
In the United States, viral meningitis is the cause of more than half of all cases of [[meningitis]].<ref>{{cite journal | vauthors = Bartt R | title = Acute bacterial and viral meningitis | journal = Continuum | volume = 18 | issue = 6 Infectious Disease | pages = 1255–70 | date = December 2012 | pmid = 23221840 | doi = 10.1212/01.CON.0000423846.40147.4f | s2cid = 24087895 }}</ref> With the prevalence of bacterial meningitis in decline, the viral disease is garnering more and more attention.<ref name=":2">{{cite journal | vauthors = McGill F, Griffiths MJ, Solomon T | title = Viral meningitis: current issues in diagnosis and treatment | journal = Current Opinion in Infectious Diseases | volume = 30 | issue = 2 | pages = 248–256 | date = April 2017 | pmid = 28118219 | doi = 10.1097/QCO.0000000000000355 | s2cid = 6003618 }}</ref> The estimated incidence has a considerable range, from 0.26 to 17 cases per 100,000 people. For enteroviral meningitis, the most common cause of viral meningitis, there are up to 75,000 cases annually in the United States alone.<ref name=":2" /> While the disease can occur in both children and adults, it is more common in children.<ref name="Viral meningitis"/>

==Signs and symptoms==
[[File:Symptoms of Meningitis.png|thumb|Symptoms of Meningitis]]
Viral meningitis characteristically presents with [[fever]], [[headache]] and [[neck stiffness]].<ref name=":1" /> Fever is the result of [[cytokines]] released that affect the thermoregulatory (temperature control) neurons of the [[hypothalamus]]. Cytokines and increased intracranial pressure stimulate [[nociceptors]] in the brain that lead to headaches. Neck stiffness is the result of inflamed meninges stretching due to [[flexion]] of the spine.<ref name=":3" /> The various layers of meninges act to form a separation between the brain and the skull.<ref>{{cite journal | vauthors = Weller RO, Sharp MM, Christodoulides M, Carare RO, Møllgård K | title = The meninges as barriers and facilitators for the movement of fluid, cells and pathogens related to the rodent and human CNS | journal = Acta Neuropathologica | volume = 135 | issue = 3 | pages = 363–385 | date = March 2018 | pmid = 29368214 | doi = 10.1007/s00401-018-1809-z | doi-access = free }}</ref> In contrast to [[bacterial meningitis]], symptoms associated with viral meningitis are often less severe and do not progress as quickly.<ref name=":1">{{Cite news|url=http://www.merckmanuals.com/home/brain,-spinal-cord,-and-nerve-disorders/meningitis/viral-meningitis|title=Viral Meningitis - Brain, Spinal Cord, and Nerve Disorders - Merck Manuals Consumer Version|work=Merck Manuals Consumer Version|access-date=2017-03-04|language=en-US}}</ref> Nausea, vomiting and [[photophobia]] (light sensitivity) also commonly occur, as do general signs of a viral infection, such as muscle aches and [[malaise]].<ref name=":1" /> Increased cranial pressure from viral meningitis stimulates the [[area postrema]], which causes nausea and vomiting. Widened pulse pressure (systolic - diastolic blood pressure), bradycardia, and irregular respiration would be alarming for Cushing's reflex, a sign of acutely elevated intracranial pressure.<ref>{{cite book | vauthors = Dinallo S, Waseem M | chapter = Cushing Reflex | date = 2019 | pmid = 31747208 | chapter-url = http://www.ncbi.nlm.nih.gov/books/NBK549801/ | access-date = 2020-01-16 | publisher = StatPearls Publishing | title = StatPearls }}</ref> Photophobia is due to meningeal irritation.<ref name=":3" /> In severe cases, people may experience concomitant [[encephalitis]] ([[meningoencephalitis]]), which is suggested by symptoms such as altered mental status, [[seizures]] or [[focal neurologic deficits]].<ref name=":5" />

Babies with viral meningitis may only appear irritable, sleepy or have trouble eating.<ref name="CDC2017">{{Cite web|url=https://www.cdc.gov/meningitis/viral.html|title=Meningitis {{!}} Viral {{!}} CDC|website=www.cdc.gov|language=en-us|access-date=2017-03-02}}</ref> Infection in the neonatal period may be the result of infection during pregnancy.<ref name="Viral meningitis"/> In severe cases, people may experience concomitant [[encephalitis]] ([[meningoencephalitis]]), which is suggested by symptoms such as altered mental status, [[seizures]] or [[focal neurologic deficits]].<ref name=":5">{{cite book | vauthors = Cho TA, Mckendall RR | title = Neurovirology | chapter = Clinical approach to the syndromes of viral encephalitis, myelitis, and meningitis | series = Handbook of Clinical Neurology | volume = 123 | pages = 89–121 | date = 2014-01-01 | pmid = 25015482 | doi = 10.1016/B978-0-444-53488-0.00004-3 | publisher = Elsevier | isbn = 9780444534880 | veditors = Tselis AC, Booss J }}</ref> The pediatric population may show some additional signs and symptoms that include [[jaundice]] and bulging [[fontanelles]].<ref name=":3" /> A biphasic fever is more often seen in children compared to adults. The first fever arrives with the onset of general constitutional symptoms, and the second accompanying the onset of the neurological symptoms.<ref name=":7">{{cite book | vauthors = Cantu RM, Das JM | chapter = Viral Meningitis | date = 2019 | pmid = 31424801 | chapter-url = http://www.ncbi.nlm.nih.gov/books/NBK545217/ | access-date = 2020-01-16 | title = StatPearls Publishing | work = StatPearls }}</ref>

Symptoms can vary depending on the virus responsible for infection. Enteroviral meningitis (the most common cause) typically presents with the classic headache, photophobia, fever, nausea, vomiting, and nuchal rigidity.<ref name=":6" /> With coxsackie and echo virus' specifically, a maculopapular rash may be present, or even the typical vesicles seen with [[Herpangina]].<ref name=":6" /> Lymphocytic choriomeningitis virus (LCMV) can be differentiated from the common presenting meningeal symptoms by the appearance of a prodromal influenza-like sickness about 10 days before other symptoms begin.<ref name=":6" /> Mumps meningitis can present similarly to isolated [[mumps]], with possible parotid and testicular swelling.<ref name=":6" /> Interestingly, research has shown that HSV-2 meningitis most often occurs in people with no history of genital herpes, and that a severe frontal headache is among the most common presenting symptoms.<ref>{{cite journal | vauthors = Landry ML, Greenwold J, Vikram HR | title = Herpes simplex type-2 meningitis: presentation and lack of standardized therapy | language = en | journal = The American Journal of Medicine | volume = 122 | issue = 7 | pages = 688–91 | date = July 2009 | pmid = 19559173 | doi = 10.1016/j.amjmed.2009.02.017 | url = https://www.amjmed.com/article/S0002-9343(09)00289-7/abstract }}</ref><ref name=":6" /> Patients with varicella zoster meningitis may present with herpes zoster ([[Shingles]]) in conjunction with classic meningeal signs.<ref name=":6" /> Meningitis can be an indication that an individual with HIV is undergoing seroconversion, the time when the human body is forming antibodies in response to the virus.<ref name="Viral meningitis"/>

== Causes ==
The most common causes of viral meningitis in the United States are non-polio [[enteroviruses]]. The viruses that cause meningitis are typically acquired from sick contacts. However, in most cases, people infected with viruses that may cause meningitis do not actually develop meningitis.<ref name=CDC2017 />

[[Viruses]] that can cause meningitis include:<ref name="eMed">{{EMedicine|article|1168529|Viral Meningitis}}</ref>
{{columns-list|colwidth=30em|
* [[Enterovirus]]es
** [[Enterovirus 71]]
** [[Echovirus]]
** [[Poliovirus]] (PV1, PV2, PV3)
** [[Coxsackie A virus]] (CAV); also causes [[Hand foot and mouth disease]]
* [[Herpesviridae]] (HHV)
** [[Herpes simplex virus]] type 1 (HSV-1 / HHV-1) or type 2 (HSV-2 / HHV-2); also cause cold sores or genital herpes
** [[Varicella zoster]] (VZV / HHV-3); also causes [[chickenpox]] and shingles ([[herpes zoster]])
** [[Epstein–Barr virus]] (EBV / HHV-4); also causes [[infectious mononucleosis]]/"mono"
** [[Cytomegalovirus]] (CMV / HHV-5)
* [[Human immunodeficiency virus]] (HIV); causes [[AIDS]]
* [[La Crosse virus]]
* [[Lymphocytic choriomeningitis virus]] (LCMV)
* [[Measles]]
* [[Mumps]]
* [[St. Louis encephalitis|St. Louis encephalitis virus]]
* [[West Nile virus]]
}}

==Mechanism==
[[File:Meningitis.webm|thumb|Meningitis]]
Viral Meningitis is mostly caused by an [[infectious agent]] that has colonized somewhere in its [[Host organism|host]].<ref name=":0">{{Cite journal|date=2017-11-29|title=Viral Meningitis: Background, Pathophysiology, Etiology|url=https://emedicine.medscape.com/article/1168529-overview}}</ref> People who are already in an immunocompromised state are at the highest risk of pathogen entry.<ref name=":3">{{Cite web|url=http://www.pathophys.org/meningitis/|title=Meningitis {{!}} McMaster Pathophysiology Review|website=www.pathophys.org|language=en-US|access-date=2017-12-12}}</ref> Some of the most common examples of immunocompromised individuals include those with HIV, cancer, diabetes, malnutrition, certain genetic disorders, and patients on chemotherapy.<ref name=":3" /> Potential sites for this include the skin, [[respiratory tract]], [[gastrointestinal tract]], [[nasopharynx]], and [[genitourinary tract]]. The organism invades the [[submucosa]] at these sites by invading host defenses, such as local immunity, physical barriers, and [[phagocytes]] or [[macrophages]].<ref name=":0" /> After pathogen invasion, the immune system is activated.<ref name=":3"/> An [[infectious agent]] can enter the [[central nervous system]] and cause meningeal disease via invading the bloodstream, a retrograde neuronal pathway, or by direct contiguous spread.<ref>{{Cite book|chapter-url=https://www.ncbi.nlm.nih.gov/books/NBK8423/|title=Medical Microbiology|last=Klimpel|first=Gary R.|date=1996|publisher=University of Texas Medical Branch at Galveston|isbn=978-0963117212|editor-last=Baron|editor-first=Samuel|edition=4th|location=Galveston (TX)|pmid=21413332|chapter=Immune Defenses}}</ref> Immune cells and damaged [[endothelial cells]] release [[matrix metalloproteinases]] (MMPs), [[cytokines]], and [[nitric oxide]]. MMPs and NO induce [[vasodilation]] in the [[cerebral vasculature]]. Cytokines induce [[capillary]] wall changes in the [[blood brain barrier]], which leads to expression of more [[leukocyte]] receptors, thus increasing white blood cell binding and [[extravasation]].<ref name=":3" />

The barrier that the [[meninges]] create between the [[brain]] and the [[bloodstream]] are what normally protect the brain from the body's [[immune system]]. Damage to the [[meninges]] and [[endothelial cells]] increases [[cytotoxic]] [[reactive oxygen species]] production, which damages pathogens as well as nearby cells.<ref name=":3" /> In [[meningitis]], the barrier is disrupted, so once viruses have entered the brain, they are isolated from the immune system and can spread.<ref>{{cite journal | vauthors = Chadwick DR | title = Viral meningitis | journal = British Medical Bulletin | volume = 75–76 | issue = 1 | pages = 1–14 | date = 2005-01-01 | pmid = 16474042 | doi = 10.1093/bmb/ldh057 | doi-access = free }}</ref> This leads to elevated [[intracranial]] pressure, cerebral [[edema]], meningeal irritation, and neuronal death.<ref name=":3" />

==Diagnosis==
[[File:Blausen 0617 LumbarPuncture.png|thumb|Lumbar Puncture]]
The diagnosis of viral meningitis is made by clinical history, physical exam, and several diagnostic tests.<ref>{{Cite web|url=http://www.mayoclinic.org/diseases-conditions/meningitis/diagnosis-treatment/diagnosis/dxc-20169577|title=Diagnosis - Meningitis - Mayo Clinic|website=www.mayoclinic.org|language=en|access-date=2017-03-04}}</ref> [[Kernig's sign|Kernig]] and [[Brudziński's sign|Brudzinski]] signs may be elucidated with specific physical exam maneuvers, and can help diagnose meningitis at the bedside.<ref name=":6">{{cite journal | vauthors = Wright WF, Pinto CN, Palisoc K, Baghli S | title = Viral (aseptic) meningitis: A review | journal = Journal of the Neurological Sciences | volume = 398 | pages = 176–183 | date = March 2019 | pmid = 30731305 | doi = 10.1016/j.jns.2019.01.050 | s2cid = 72334384 }}</ref> Most importantly however, [[cerebrospinal fluid]] (CSF) is collected via [[lumbar puncture]] (also known as spinal tap). This fluid, which normally surrounds the brain and spinal cord, is then analyzed for signs of infection.<ref name=":4">{{Cite web|url=https://medlineplus.gov/ency/article/003369.htm|title=CSF analysis: MedlinePlus Medical Encyclopedia|website=medlineplus.gov|language=en|access-date=2017-03-04}}</ref> CSF findings that suggest a viral cause of meningitis include an elevated [[white blood cell]] count (usually 10-100  cells/μL) with a [[Lymphocytic pleocytosis|lymphocytic]] predominance in combination with a normal [[glucose]] level.<ref>{{Cite web|url=https://wiki.umms.med.umich.edu/display/NEURO/CSF+Analysis|title=CSF Analysis - Neurology - UMMS Confluence|website=wiki.umms.med.umich.edu|access-date=2017-03-04|archive-date=2017-03-05|archive-url=https://web.archive.org/web/20170305120539/https://wiki.umms.med.umich.edu/display/NEURO/CSF+Analysis|url-status=dead}}</ref> Increasingly,  cerebrospinal fluid [[Polymerase chain reaction|PCR]] tests have become especially useful for diagnosing viral meningitis, with an estimated sensitivity of 95-100%.<ref>{{Cite journal|url=http://www.aafp.org/afp/2003/0915/p1103.html|title=Cerebrospinal Fluid Analysis |issue=6|pages=1103–1108|last=Fomin|first=Dean A. Seehusen{{!}}Mark Reeves{{!}}Demitri|journal=American Family Physician|volume=68|language=en|access-date=2017-03-04|date=2003-09-15|pmid=14524396 }}</ref> Additionally, samples from the stool, urine, blood and throat can also help to identify viral meningitis.<ref name=":4" /> CSF vs serum c-reactive protein and procalcitonin have not been shown to elucidate whether meningitis is bacterial or viral.<ref name=":7" />

In certain cases, a [[CT scan]] of the head should be done before a [[lumbar puncture]] such as in those with poor immune function or those with increased [[intracranial pressure]].<ref name="Viral meningitis"/> If the patient has focal neurological deficits, [[papilledema]], a [[Glasgow Coma Scale|Glasgow Coma Score]] less than 12, or a recent history of seizures, lumbar puncture should be reconsidered.<ref name=":7" />

Differential diagnosis for viral meningitis includes meningitis caused by bacteria, mycoplasma, fungus, and drugs such as NSAIDS, TMP-SMX, IVIG. Further considerations include brain tumors, lupus, vasculitis, and Kawasaki disease in the pediatric population.<ref name=":7" />

==Treatment==
[[File:Aciclovir 2D structure.svg|thumb|Aciclovir]]
Because there is no clinical differentiation between bacterial and viral meningitis, people with suspected disease should be sent to the hospital for further evaluation.<ref name="Viral meningitis"/> Treatment for viral meningitis is generally [[supportive care|supportive]]. Rest, hydration, [[antipyretics]], and pain or anti-inflammatory medications may be given as needed.<ref>{{Cite journal|date=2017-11-29|title=Viral Meningitis Treatment & Management: Approach Considerations, Pharmacologic Treatment and Medical Procedures, Patient Activity|url=https://emedicine.medscape.com/article/1168529-treatment}}</ref> However, if there is initial uncertainty as to whether the meningitis is bacterial or viral in origin, empiric antibiotics are often given until bacterial infection is ruled out.<ref name=":7" />

[[Herpes simplex virus]], [[varicella zoster virus]] and [[cytomegalovirus]] have a specific antiviral therapy. For [[herpes]] the treatment of choice is [[aciclovir]].<ref name="acyclovir">{{cite journal | vauthors = Tyler KL | title = Herpes simplex virus infections of the central nervous system: encephalitis and meningitis, including Mollaret's | journal = Herpes | volume = 11 | issue = Suppl 2 | pages = 57A–64A | date = June 2004 | pmid = 15319091 }}</ref> If encephalitis is suspected, empiric treatment with IV aciclovir is often warranted.<ref name=":7" />

Surgical management is indicated where there is extremely increased intracranial pressure, infection of an adjacent bony structure (e.g. [[mastoiditis]]), skull fracture, or [[abscess]] formation.<ref name=":3" />

The majority of people that have viral meningitis get better within 7–10 days.<ref>{{Cite web|url=https://www.cdc.gov/meningitis/viral.html|title=Meningitis {{!}} Viral {{!}} CDC|date=2017-12-04|website=www.cdc.gov|language=en-us|access-date=2017-12-11}}</ref>

==Epidemiology==
From 1988 to 1999, about 36,000 cases occurred each year in the United States.<ref>{{cite journal | vauthors = Khetsuriani N, Quiroz ES, Holman RC, Anderson LJ | title = Viral meningitis-associated hospitalizations in the United States, 1988-1999 | journal = Neuroepidemiology | volume = 22 | issue = 6 | pages = 345–52 | date = Nov–Dec 2003 | pmid = 14557685 | doi = 10.1159/000072924 | s2cid = 27311344 | url = https://zenodo.org/record/1235329 }}</ref> As recently as 2017, the incidence in the U.S. alone increased to 75,000 cases per year for enteroviral meningitis.<ref name=":2" /> With the advent and implementation of vaccinations for organisms such as ''Streptococcus pneumoniae, Haemophilus influenza'' type B, and ''Neisseria meningitis'', rates of bacterial meningitis have been in decline, making viral meningitis more common.<ref name=":7" /> Countries without high rates of immunization still carry higher rates of bacterial disease.<ref name=":7" /> While the disease can occur in both children and adults, it is more common in children.<ref name="Viral meningitis"/> Rates of infection tend to reach a peak in the summer and fall.<ref>{{cite journal | vauthors = Logan SA, MacMahon E | title = Viral meningitis | journal = BMJ | volume = 336 | issue = 7634 | pages = 36–40 | date = January 2008 | pmid = 18174598 | pmc = 2174764 | doi = 10.1136/bmj.39409.673657.AE }}</ref> During an outbreak in Romania and in Spain viral meningitis was more common among adults.<ref name="ReferenceA">{{cite journal | vauthors = Jiménez Caballero PE, Muñoz Escudero F, Murcia Carretero S, Verdú Pérez A | title = Descriptive analysis of viral meningitis in a general hospital: differences in the characteristics between children and adults | journal = Neurologia | volume = 26 | issue = 8 | pages = 468–73 | date = October 2011 | pmid = 21349608 | doi = 10.1016/j.nrleng.2010.12.004 | doi-access = free }}</ref> While, people aged younger than 15 made up 33.8% of cases.<ref name="ReferenceA" /> In contrast in Finland in 1966 and in Cyprus in 1996, Gaza 1997, China 1998 and Taiwan 1998, the incidence of viral meningitis was higher among children.<ref>{{cite journal | vauthors = Rantakallio P, Leskinen M, von Wendt L | title = Incidence and prognosis of central nervous system infections in a birth cohort of 12,000 children | journal = Scandinavian Journal of Infectious Diseases | volume = 18 | issue = 4 | pages = 287–94 | date = 1986 | pmid = 3764348 | doi = 10.3109/00365548609032339 }}</ref><ref>{{cite web|url=https://www.who.int/csr/don/1998_07_04/en/|archive-url=https://web.archive.org/web/20040529203651/http://www.who.int/csr/don/1998_07_04/en/|url-status=dead|archive-date=May 29, 2004|title=1998—Enterovirus Outbreak in Taiwan, China—update no. 2|website=WHO}}</ref><ref>{{cite web|url=https://www.who.int/csr/don/1997_07_07/en/|archive-url=https://web.archive.org/web/20040710104059/http://www.who.int/csr/don/1997_07_07/en/|url-status=dead|archive-date=July 10, 2004|title=1997—Viral meningitis in Gaza|website=WHO}}</ref><ref>{{cite web|url=https://www.who.int/csr/don/1996_08_12b/en/|archive-url=https://web.archive.org/web/20040710105212/http://www.who.int/csr/don/1996_08_12b/en/|url-status=dead|archive-date=July 10, 2004|title=1996—Viral meningitis in Cyprus|website=WHO}}</ref>

==Recent research==

It has been proposed that viral meningitis might lead to inflammatory injury of the vertebral [[artery wall]].<ref>{{Cite journal|last=Pan|first=Xudong|title=Vertebral artery dissection associated with viral meningitis|journal=BMC Neurology|year=2012|volume=12|pages=79|doi=10.1186/1471-2377-12-79|pmid=22909191|pmc=3466159 |doi-access=free }}</ref>

The Meningitis Research Foundation is conducting a study to see if new [[genomic]] techniques can improve the speed, accuracy and cost of diagnosing meningitis in children in the UK. The research team will develop a new method to be used for the diagnosis of meningitis, analysing the genetic material of [[microorganisms]] found in [[Cerebrospinal fluid|CSF]] (cerebrospinal fluid). The new method will first be developed using CSF samples where the microorganism is known, but then will be applied to CSF samples where the microorganism is unknown (estimated at around 40%) to try and identify a cause.<ref>{{Cite web|url=https://www.meningitis.org/research-projects/genomic-techniques-identify-causes-of-meningitis|title=Using new genomic techniques to identify the causes of meningitis in UK children {{!}} Meningitis Research Foundation|website=www.meningitis.org|access-date=2017-12-12}}</ref> There is also research investigating whether [[High throughput sequencing|high-throughput sequencing]], wherein the investigator does not need to compare DNA results with known genomic sequences, could be used in specifically diagnosing unknown causes of viral meningitis.<ref>{{cite journal | vauthors = Zanella MC, Lenggenhager L, Schrenzel J, Cordey S, Kaiser L | title = High-throughput sequencing for the aetiologic identification of viral encephalitis, meningoencephalitis, and meningitis. A narrative review and clinical appraisal | language = en | journal = Clinical Microbiology and Infection | volume = 25 | issue = 4 | pages = 422–430 | date = April 2019 | pmid = 30641229 | doi = 10.1016/j.cmi.2018.12.022 | url = https://www.clinicalmicrobiologyandinfection.com/article/S1198-743X(18)30812-7/abstract | doi-access = free | pmc = 7129948 }}</ref>

While there is some emerging evidence that bacterial meningitis may have a negative impact on cognitive function, there is no such evidence for viral meningitis.<ref>{{cite journal | vauthors = Christie D, Rashid H, El-Bashir H, Sweeney F, Shore T, Booy R, Viner RM | title = Impact of meningitis on intelligence and development: A systematic review and meta-analysis | journal = PLOS ONE | volume = 12 | issue = 8 | pages = e0175024 | date = 2017 | pmid = 28837564 | pmc = 5570486 | doi = 10.1371/journal.pone.0175024 | bibcode = 2017PLoSO..1275024C | doi-access = free }}</ref>

== References ==
{{reflist}}

== External links ==
{{Medical resources
| DiseasesDB      =
| ICD10           = {{ICD10|G|0|2}}
| ICD9            = {{ICD9|321.2}}
| ICDO            =
| OMIM            =
| MedlinePlus     =
| eMedicineSubj   = article
| eMedicineTopic  = 1168529
| MeshID          = D008587
| ICD10CM         = {{ICD10CM|A87}}
}}
{{Viral diseases}}
{{Diseases of meninges}}

[[Category:Meningitis]]
[[Category:Viral infections of the central nervous system]]
[[Category:Enterovirus-associated diseases]]