Viral meningitis characteristically presents with fever, headache and neck stiffness. Fever is the result of cytokines released that affect the thermoregulatory 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. In contrast to bacterial meningitis, symptoms are often less severe and do not progress as quickly. Nausea, vomiting and photophobia (light sensitivity) also commonly occur, as do general signs of a viral infection, such as muscle aches and malaise. Increased cranial pressure from viral meningitis stimulates the area postrema, which causes nausea and vomiting. Photophobia is due to meningeal irritation. In severe cases, people may experience concomitant encephalitis (meningoencephalitis), which is suggested by symptoms such as altered mental status, seizures or focal neurologic deficits.

Babies with viral meningitis may only appear irritable, sleepy or have trouble eating. In severe cases, people may experience concomitant encephalitis (meningoencephalitis), which is suggested by symptoms such as altered mental status, seizures or focal neurologic deficits. The pediatric population may show some additional signs and symptoms that include jaundice and bulging fontanelles.

Although DNA analysis techniques such as Polymerase chain reaction can be used to look for DNA of herpesviruses in spinal fluid or blood, the results may be negative, even in cases where other definitive symptoms exist.

Mollaret's meningitis is characterized by chronic, recurrent episodes of headache, stiff neck, meningismus, and fever; cerebrospinal fluid (CSF) pleocytosis with large "endothelial" cells, neutrophil granulocytes, and lymphocytes; and attacks separated by symptom-free periods of weeks to years; and spontaneous remission of symptoms and signs. Many people have side effects between bouts that vary from chronic daily headaches to after-effects from meningitis such as hearing loss and visual impairment, nerve pain and twitches. Symptoms may be mild or severe. Some cases may be short, lasting only 3–7 days, while others last for weeks to months.

While herpes simplex and varicella can cause rash, Mollaret's patients may or may not have a rash. Herpes simplex virus is likely the most common cause of Mollaret's meningitis.

Herpesviral meningitis is meningitis associated with herpes simplex virus (HSV).

HSV-2 is the most common cause of Mollaret's meningitis, a type of recurrent viral meningitis. This condition was first described in 1944 by French neurologist Pierre Mollaret. Recurrences usually last a few days or a few weeks, and resolve without treatment. They may recur weekly or monthly for approximately 5 years following primary infection.

Most individuals with HSE show a decrease in their level of consciousness and an altered mental state presenting as confusion, and changes in personality. Increased numbers of white blood cells can be found in patient's cerebrospinal fluid, without the presence of pathogenic bacteria and fungi. Patients typically have a fever and may have seizures. The electrical activity of the brain changes as the disease progresses, first showing abnormalities in one temporal lobe of the brain, which spread to the other temporal lobe 7–10 days later. Imaging by CT or MRI shows characteristic changes in the temporal lobes (see Figure). Definite diagnosis requires testing of the cerebrospinal fluid (CSF) by a lumbar puncture (spinal tap) for presence of the virus. The testing takes several days to perform, and patients with suspected Herpes encephalitis should be treated with acyclovir immediately while waiting for test results.

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, sensitivity to light, and neck stiffness.

Viruses are the most common cause of aseptic meningitis. Most cases of viral meningitis are caused by enteroviruses (common stomach viruses). However, other viruses can also cause viral meningitis. For instance, West Nile virus, mumps, measles, herpes simplex types I and II, varicella, and lymphocytic choriomeningitis (LCM) virus. 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.

In most causes there is no specific treatment, with efforts generally aimed at relieving symptoms (headache, fever, or nausea). A few viral causes, such as HSV, have specific treatments.

In the United States viral meningitis is the cause of greater than half of all cases of meningitis. From 1988–1999, about 36,000 cases occurred a year. While the disease can occur in both children and adults it is more common in children.

Characteristics of a viral infection can include pain, swelling, redness, impaired function, fever, drowsiness, confusion and convulsions.

Mollaret's meningitis is a recurrent or chronic inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges. Since Mollaret's meningitis is a recurrent, benign (non-cancerous), aseptic meningitis, it is now referred to as benign recurrent lymphocytic meningitis. It was named for Pierre Mollaret, the French neurologist who first described it in 1944.

Although chronic meningitis has been defined as "irritation and inflammation of the meninges persisting for more than 4 weeks being associated with pleocytosis in the cerebrospinal fluid", cerebrospinal fluid abnormalities may not be detectable for the entire time. Diagnosis can be elusive, as Helbok et al. note: "in reality, many more weeks, even months pass by until the diagnosis is established. In many cases the signs and symptoms of chronic meningitis not only persist for periods longer than 4 weeks, they even progress with continuing deterioration, i. e. headache, neck stiffness and even low grade fever. Impairment of consciousness, epileptic seizures, neurological signs and symptoms may evolve over time."

The earliest symptoms of shingles, which include headache, fever, and malaise, are nonspecific, and may result in an incorrect diagnosis. These symptoms are commonly followed by sensations of burning pain, itching, hyperesthesia (oversensitivity), or paresthesia ("pins and needles": tingling, pricking, or numbness). Pain can be mild to extreme in the affected dermatome, with sensations that are often described as stinging, tingling, aching, numbing or throbbing, and can be interspersed with quick stabs of agonizing pain.

Shingles in children is often painless, but people are more likely to get shingles as they age, and the disease tends to be more severe.

In most cases after one to two days, but sometimes as long as three weeks, the initial phase is followed by the appearance of the characteristic skin rash. The pain and rash most commonly occurs on the torso, but can appear on the face, eyes or other parts of the body. At first the rash appears similar to the first appearance of hives; however, unlike hives, shingles causes skin changes limited to a dermatome, normally resulting in a stripe or belt-like pattern that is limited to one side of the body and does not cross the midline. "Zoster sine herpete" ("zoster without herpes") describes a person who has all of the symptoms of shingles except this characteristic rash.

Later the rash becomes vesicular, forming small blisters filled with a serous exudate, as the fever and general malaise continue. The painful vesicles eventually become cloudy or darkened as they fill with blood, and crust over within seven to ten days; usually the crusts fall off and the skin heals, but sometimes, after severe blistering, scarring and discolored skin remain.

Herpesviral encephalitis is encephalitis due to herpes simplex virus.

Herpes simplex encephalitis (HSE) is a viral infection of the human central nervous system. It is estimated to affect at least 1 in 500,000 individuals per year and some studies suggest an incidence rate of 5.9 cases per 100,000 live births. The majority of cases of herpes encephalitis are caused by herpes simplex virus-1 (HSV-1), the same virus that causes cold sores. 57% of American adults are infected with HSV-1, which is spread through droplets, casual contact, and sometimes sexual contact, though most infected people never have cold sores. About 10% of cases of herpes encephalitis are due to HSV-2, which is typically spread through sexual contact. About 1 in 3 cases of HSE result from primary HSV-1 infection, predominantly occurring in individuals under the age of 18; 2 in 3 cases occur in seropositive persons, few of whom have history of recurrent orofacial herpes. Approximately 50% of individuals who develop HSE are over 50 years of age.

Shingles may have additional symptoms, depending on the dermatome involved. The trigeminal nerve is the most commonly involved nerve, of which the ophthalmic division is the most commonly involved branch. When the virus is reactivated in this nerve branch it is termed "zoster ophthalmicus". The skin of the forehead, upper eyelid and orbit of the eye may be involved. Zoster ophthalmicus occurs in approximately 10% to 25% of cases. In some people, symptoms may include conjunctivitis, keratitis, uveitis, and optic nerve that can sometimes cause chronic ocular inflammation, loss of vision, and debilitating pain.

"Shingles oticus", also known as Ramsay Hunt syndrome type II, involves the ear. It is thought to result from the virus spreading from the facial nerve to the vestibulocochlear nerve. Symptoms include hearing loss and vertigo (rotational dizziness).

Shingles may occur in the mouth if the maxillary or mandibular division of the trigeminal nerve is affected, in which the rash may appear on the mucous membrane of the upper jaw (usually the palate, sometimes the gums of the upper teeth) or the lower jaw (tongue or gums of the lower teeth) respectively. Oral involvement may occur alone or in combination with a rash on the skin over the cutaneous distribution of the same trigeminal branch. As with shingles of the skin, the lesions tend to only involve one side, distinguishing it from other oral blistering conditions. In the mouth, shingles appears initially as 1–4 mm opaque blisters (vesicles), which break down quickly to leave ulcers that heal within 10–14 days. The prodromal pain (before the rash) may be confused with toothache. Sometimes this leads to unnecessary dental treatment. Post herpetic neuralgia uncommonly is associated with shingles in the mouth. Unusual complications may occur with intra-oral shingles that are not seen elsewhere. Due to the close relationship of blood vessels to nerves, the virus can spread to involve the blood vessels and compromise the blood supply, sometimes causing ischemic necrosis. Therefore, oral involvement rarely causes complications such as osteonecrosis, tooth loss, periodontitis (gum disease), pulp calcification, pulp necrosis, periapical lesions and tooth developmental anomalies.

The most common diseases caused by acute viral infections are encephalitis, flaccid paralysis, aseptic meningitis, post infectious and encephalomyelitis.

Adult patients with encephalitis present with acute onset of fever, headache, confusion, and sometimes seizures. Younger children or infants may present irritability, poor appetite and fever.

Neurological examinations usually reveal a drowsy or confused patient. Stiff neck, due to the irritation of the meninges covering the brain, indicates that the patient has either meningitis or meningoencephalitis.

Encephalitis lethargica is identified by high fever, headache, delayed physical response, and lethargy. Individuals can exhibit upper body weakness, muscular pains, and tremors, though the cause of encephalitis lethargica is not currently known. From 1917 to 1928, an epidemic of encephalitis lethargica occurred worldwide.

Symptoms develop over days or weeks. The subacute development of short-term memory deficits is considered the hallmark of this disease, but this symptom is often overlooked, because it is overshadowed by other more obvious symptoms such as headache, irritability, sleep disturbance, delusions, hallucinations, agitation, seizures and psychosis, or because the other symptoms mean the patient has to be sedated, and it is not possible to test memory in a sedated patient.

It takes 5 to 15 days after the bite of an infected mosquito to develop symptoms of LACV disease. Symptoms include nausea, headache, vomiting in milder cases and seizures, coma, paralysis and permanent brain damage in severe cases.

LAC encephalitis initially presents as a nonspecific summertime illness with fever, headache, nausea, vomiting and lethargy. Severe disease occurs most commonly in children under the age of 16 and is characterized by seizures, coma, paralysis, and a variety of neurological sequelae after recovery. Death from LAC encephalitis occurs in less than 1% of clinical cases. In many clinical settings, pediatric cases presenting with CNS involvement are routinely screened for herpes or enteroviral causes. Since there is no specific treatment for LAC encephalitis, physicians often do not request the tests required to specifically identify LAC virus, and the cases are reported as aseptic meningitis or viral encephalitis of unknown cause.

As with many infections, the very young, the very old and the immunocompromised are at a higher risk of developing severe symptoms.

The following is a list of common signs and symptoms found with neonatal meningitis.

- Fever

- poor appetite

- anterior fontanelle bulging

- seizure

- jitteriness

- dyspnea

- irritability

- anorexia

- vomiting

- diarrhea

- abdominal distention (increase in abdominal size)

- neck rigidity

- cyanosis

- jaundice

- and sunset eyes (downward gaze of the eyes)

- abnormal body temperature (hypo-or hyperthermia)

- change of activity (lethargy or irritability)

Unfortunately these symptoms are unspecific and may point to many different conditions.

Though caused by different infections, the signs and symptoms of TORCH syndrome are consistent. They include hepatosplenomegaly (enlargement of the liver and spleen), fever, lethargy, difficulty feeding, anemia, petechiae, purpurae, jaundice, and chorioretinitis. The specific infection may cause additional symptoms.

TORCH syndrome may develop before birth, causing stillbirth, in the neonatal period, or later in life.

Meningoencephalitis (; from Greek μῆνιγξ "meninx", "membrane", ἐγκέφαλος, "enképhalos" "brain", and the medical suffix "-itis", "inflammation") is a medical condition that simultaneously resembles both meningitis, which is an infection or inflammation of the meninges, and encephalitis, which is an infection or inflammation of the brain.

Causative organisms include protozoans, viral and bacterial pathogens.

Specific types include:

In adults, the most common symptom of meningitis is a severe headache, occurring in almost 90% of cases of bacterial meningitis, followed by nuchal rigidity (the inability to flex the neck forward passively due to increased neck muscle tone and stiffness). The classic triad of diagnostic signs consists of nuchal rigidity, sudden high fever, and altered mental status; however, all three features are present in only 44–46% of bacterial meningitis cases. If none of the three signs are present, acute meningitis is extremely unlikely. Other signs commonly associated with meningitis include photophobia (intolerance to bright light) and phonophobia (intolerance to loud noises). Small children often do not exhibit the aforementioned symptoms, and may only be irritable and look unwell. The fontanelle (the soft spot on the top of a baby's head) can bulge in infants aged up to 6 months. Other features that distinguish meningitis from less severe illnesses in young children are leg pain, cold extremities, and an abnormal skin color.

Nuchal rigidity occurs in 70% of bacterial meningitis in adults. Other signs include the presence of positive Kernig's sign or Brudziński sign. Kernig's sign is assessed with the person lying supine, with the hip and knee flexed to 90 degrees. In a person with a positive Kernig's sign, pain limits passive extension of the knee. A positive Brudzinski's sign occurs when flexion of the neck causes involuntary flexion of the knee and hip. Although Kernig's sign and Brudzinski's sign are both commonly used to screen for meningitis, the sensitivity of these tests is limited. They do, however, have very good specificity for meningitis: the signs rarely occur in other diseases. Another test, known as the "jolt accentuation maneuver" helps determine whether meningitis is present in those reporting fever and headache. A person is asked to rapidly rotate the head horizontally; if this does not make the headache worse, meningitis is unlikely.

Other problems can produce symptoms similar to those above, but from non-meningitic causes. This is called meningism or pseudomeningitis.

Meningitis caused by the bacterium "Neisseria meningitidis" (known as "meningococcal meningitis") can be differentiated from meningitis with other causes by a rapidly spreading petechial rash, which may precede other symptoms. The rash consists of numerous small, irregular purple or red spots ("petechiae") on the trunk, lower extremities, mucous membranes, conjuctiva, and (occasionally) the palms of the hands or soles of the feet. The rash is typically non-blanching; the redness does not disappear when pressed with a finger or a glass tumbler. Although this rash is not necessarily present in meningococcal meningitis, it is relatively specific for the disease; it does, however, occasionally occur in meningitis due to other bacteria. Other clues on the cause of meningitis may be the skin signs of hand, foot and mouth disease and genital herpes, both of which are associated with various forms of viral meningitis.

Aseptic meningitis, or sterile meningitis, is a condition in which the layers lining the brain, the meninges, become inflamed and a pyogenic bacterial source is not to blame. Meningitis is diagnosed on a history of characteristic symptoms and certain examination findings (e.g., Kernig's sign). Investigations should show an increase in the number of leukocytes present in the cerebrospinal fluid (CSF) obtained via lumbar puncture (normally being fewer than five visible leukocytes per microscopic high-power field).

The term "aseptic" is frequently a misnomer, implying a lack of infection. On the contrary, many cases of aseptic meningitis represent infection with viruses or mycobacteria that cannot be detected with routine methods. While the advent of polymerase chain reaction has increased the ability of clinicians to detect viruses such as enterovirus, cytomegalovirus, and herpes virus in the CSF, many viruses can still escape detection. Additionally, mycobacteria frequently require special stains and culture methods that make their detection difficult. When CSF findings are consistent with meningitis, and microbiologic testing is unrevealing, clinicians typically assign the diagnosis of aseptic meningitis—making it a relative diagnosis of exclusion.

Aseptic meningitis can result from non-infectious causes as well. it can be a relatively infrequent side effect of medications, or be a result of an autoimmune disease. There is no formal classification system of aseptic meningitis except to state the underlying cause, if known. The absence of bacteria found in the spinal fluid upon spinal tap, either through microscopic examination or by culture, usually differentiates aseptic meningitis from its pyogenic counterpart.

"Aseptic meningitis", like non-gonococcal urethritis, non-Hodgkin lymphoma and atypical pneumonia, merely states what the condition is not, rather than what it is. Terms such as viral meningitis, bacterial meningitis, fungal meningitis, neoplastic meningitis and drug-induced aseptic meningitis can provide more information about the condition, and without using one of these more specific terms, it is difficult to describe treatment options or prognosis.

Neonatal herpes simplex is a HSV infection in an infant. It is a rare but serious condition, usually caused by vertical transmission of HSV-1 or -2) from mother to newborn. During immunodeficiency, herpes simplex can cause unusual lesions in the skin. One of the most striking is the appearance of clean linear erosions in skin creases, with the appearance of a knife cut. Herpetic sycosis is a recurrent or initial herpes simplex infection affecting primarily the hair follicles. Eczema herpeticum is an infection with herpesvirus in patients with chronic atopic dermatitis may result in spread of herpes simples throughout the eczematous areas.

Herpetic keratoconjunctivitis, a primary infection, typically presents as swelling of the conjunctiva and eyelids (blepharoconjunctivitis), accompanied by small white itchy lesions on the surface of the cornea.

Herpetic sycosis is a recurrent or initial herpes simplex infection affecting primarily the hair follicle.

Additional problems may occur in the early stage of the illness. These may require specific treatment, and sometimes indicate severe illness or worse prognosis. The infection may trigger sepsis, a systemic inflammatory response syndrome of falling blood pressure, fast heart rate, high or abnormally low temperature, and rapid breathing. Very low blood pressure may occur at an early stage, especially but not exclusively in meningococcal meningitis; this may lead to insufficient blood supply to other organs. Disseminated intravascular coagulation, the excessive activation of blood clotting, may obstruct blood flow to organs and paradoxically increase the bleeding risk. Gangrene of limbs can occur in meningococcal disease. Severe meningococcal and pneumococcal infections may result in hemorrhaging of the adrenal glands, leading to Waterhouse-Friderichsen syndrome, which is often fatal.

The brain tissue may swell, pressure inside the skull may increase and the swollen brain may herniate through the skull base. This may be noticed by a decreasing level of consciousness, loss of the pupillary light reflex, and abnormal posturing. The inflammation of the brain tissue may also obstruct the normal flow of CSF around the brain (hydrocephalus). Seizures may occur for various reasons; in children, seizures are common in the early stages of meningitis (in 30% of cases) and do not necessarily indicate an underlying cause. Seizures may result from increased pressure and from areas of inflammation in the brain tissue. Focal seizures (seizures that involve one limb or part of the body), persistent seizures, late-onset seizures and those that are difficult to control with medication indicate a poorer long-term outcome.

Inflammation of the meninges may lead to abnormalities of the cranial nerves, a group of nerves arising from the brain stem that supply the head and neck area and which control, among other functions, eye movement, facial muscles, and hearing. Visual symptoms and hearing loss may persist after an episode of meningitis. Inflammation of the brain (encephalitis) or its blood vessels (cerebral vasculitis), as well as the formation of blood clots in the veins (cerebral venous thrombosis), may all lead to weakness, loss of sensation, or abnormal movement or function of the part of the body supplied by the affected area of the brain.

Neonatal meningitis is a serious medical condition in infants. Meningitis is an inflammation of the meninges (the protective membranes of the central nervous system (CNS)) and is more common in the neonatal period (infants less than 44 days old) than any other time in life and is an important cause of morbidity and mortality globally. Mortality is roughly half in developing countries and ranges from 8%-12.5% in developed countries.

Symptoms seen with neonatal meningitis are often unspecific that may point to several conditions, such as sepsis (whole body inflammation). These can include fever, irritability, and dyspnea. The only method to determine if meningitis is the cause of these symptoms is lumbar puncture (LP; an examination of the cerebrospinal fluid).

The most common causes of neonatal meningitis is bacterial infection of the blood, known as bacteremia (specifically Group B "Streptococci" (GBS; "Streptococcus agalactiae"), "Escherichia coli", and "Listeria monocytogenes"). Although there is a low mortality rate in developed countries, there is a 50% prevalence rate of neurodevelopmental disabilities in "E. coli" and GBS meningitis, while having a 79% prevalence for non-"E. coli" Gram-negative caused meningitis. Delayed treatment of neonatal meningitis may cause include cerebral palsy, blindness, deafness, and learning deficiencies.