Encephalitis is an acute infection and inflammation of the brain tissue.
Patients suffering from encephalitis may either have no symptoms or have mild flu-like symptoms like headache, fever, nausea, vomiting, pain in muscles or joints and fatigue or weakness. Other classical signs and symptoms of encephalitis are behavioral and personality changes with low level of consciousness, confusion, agitation or hallucinations, lethargy, seizures, neck pain and stiffness, photophobia, loss of sensation or paralysis in certain parts of the face or body, difficulty in speech and hearing, notion of foul smells like burnt meat or rotten eggs. In infants and young children, the manifestations might also consist of irritability, uncontrollable crying, poor feeding or not waking up for feeding, stiffening of the body, nausea and vomiting, bulging in the fontanels in the infants.
In addition to standard blood and urine tests, studies should be done to know the infectious agent causing the encephalitis .
Blood cultures for bacterial pathogens should be done. Herpes simplex virus (HSV) cultures of doubtful lesions should be done along with a Tzanck smear.
Spinal tap (Lumbar puncture): With the help of this procedure, the physician can examine the cerebrospinal fluid for any infection or inflammation of the brain. Diagnosis is made by detecting antibodies in the cerebrospinal fluid against a specific viral agent or by polymerase chain reaction that amplifies the RNA or DNA of the virus responsible. Serological tests may show high antibody titre against the causative antigen. The leucocyte count might be high and glucose levels might be disturbed.
Brain imaging: A CT scan of the head with and without contrast should be performed in all cases encephalitis. This should be done before performing lumbar puncture if there are focal complaints or findings, signs to search for confirmation of increased intracranial pressure, obstructive hydrocephalus, or mass effect due to focal brain infection. Head CT scanning also helps in ruling out the possibility of brain haemorrhage or infarction as a cause of the encephalopathic state. An Magnetic resonance imaging (MRI) is better than CT scanning as it offers better resolution in demonstrating brain abnormalities earlier in the disease course.
Electroencephalogram (EEG) can be done to record the electrical activity of the brain. Some peculiar patterns in this activity can be related to the diagnosis of encephalitis, for e.g. in HSE, EEG often documents characteristic paroxysmal lateral epileptiform discharges (PLEDs), even before neuroradiography changes.
Brain biopsy: In case the patient is not responding to the treatment and is still worsening, a brain biopsy may be performed to obtain samples of the brain tissue. A brain biopsy is 96% sensitive and 100% specific.
The target of treatment for acutely ill patients with viral encephalitis is receiving the first dose of acyclovir  as soon as possible. In otherwise stable patients, elevating the head and monitoring neurologic status usually are sufficient. When more aggressive treatment is indicated, early use of diuretics (e.g. furosemide 20 mg IV, mannitol 1 g/kg IV) might be helpful, provided that circulatory volume is guarded. Dexamethasone 10 mg IV every 6 hours helps in managing edema surrounding space-occupying lesions. Hyperventilation (arterial CO2 tension (PaCO2) 30 mm Hg) may cause a disproportional decrease in cerebral blood flow (CBF), but it is used to control increasing ICP on an emergency basis. Ganciclovir is another antiviral drug that is used to treat some types of herpes encephalitis.
Empiric adult emergency treatment for herpes simplex virus (HSV) meningoencephalitis and varicella-zoster virus (VZV) encephalitis consists of acyclovir 10 mg/kg (infused over 1 h) every 8 hours for 14-21 days. Physician might use acyclovir 10-15 mg/kg IV every 8 hours for neonatal HSV; for HSV encephalitis in the pediatric population, acyclovir 10 mg/kg IV every 8 hours might be used. Apart from this other encephalitis treatment aims at reducing symptoms.
After the initial illness, it may be necessary to receive additional therapy depending on the type and severity of complications. This therapy may include physical therapy, speech therapy, occupational therapy and psychotherapy.
Prognosis depends chiefly on the etiology and health status of the patient. Patients in extremes of age i.e. <1 yr or >55 yrs, immunocompromised, already suffering from neurologic conditions have poorer outcomes. Patients who remain untreated or those receiving late treatments suffer from long-term motor and mental disabilities.
Viral agents like Herpes simplex virus (HSV) type 1 and 2, Varicella zoster virus (VZV), Epstein-Barr virus, Rabies virus, Polio virus, Measles virus, Mumps virus and Rubella virus are the commonest cause of encephalitis. Human herpesvirus 6 (HHV-6) may also be a causative agent  .
Other causes include infection by flaviviruses like Japanese encephalitis virus, St. Louis encephalitis virus or the West Nile virus. Eastern equine encephalitis virus (EEE virus), Western equine encephalitis virus (WEE virus) or Venezuelan equine encephalitis virus (VEE virus), Variola minor virus and Variola major virus can also lead to encephalitis. Hendra (HeV) and Nipah (NiV),  are also known to cause viral encephalitis. Animal vectors like mosquitoes and ticks spread the arbovirus group of viruses and warm-blooded mammals are vectors for rabies and lymphocytic choriomeningitis.
Other causes of encephalitis include:
People at extremes of age are at greater risk, especially for herpes simplex encephalitis which has an incidence of 2-4 per million population per year . In Western countries, the incidence of acute encephalitis is 7.4 cases per 100,000 people yearly, whereas in tropical countries it is 6.34 . In 2010, it lead to around 120,000 deaths, whereas it caused 144,000 deaths in 1990 .
The means of entry for the causative agent are specific. Lot of viruses are transmitted by humans, although many cases of Herpes simplex encephalitis are considered to be a reactivation of HSV that was dormant in the trigeminal ganglia.
Mosquitoes or ticks inject the arbovirus and the rabies virus is passed through an infected animal bite or coming in contact with animal secretions. For viruses like VZV and cytomegalovirus (CMV), an immuno-compromised state is generally needed to develop clinically visible encephalitis. Basically, the virus replicates outside the CNS and gets entry into the CNS via hematogenous spread or by travelling along the neural pathways (e.g. rabies virus, HSV, VZV).
As soon as the virus crosses the blood-brain barrier it enters the neural cells, resulting into disturbance of cellular functioning, perivascular congestion, haemorrhage, and scattered inflammatory response which affects the gray matter over white matter unevenly. Viruses affect certain specific areas of the brain because of neuron cell membrane receptors that are found only in certain areas of the brain. For example, HSV is inclined to affect the inferior and medial temporal lobes.
In comparison with viruses that infect the gray matter, infections due to measles, EBV and CMV resulting into acute disseminated encephalitis and postinfectious encephalomyelitis are immune-mediated processes leading to multifocal demyelination of the perivenous white matter.
Vaccination is available against tick-borne encephalitis  and Japanese encephalitis  and should be considered for at-risk individuals. The risk for mosquito-borne infections is maximum between dusk and dawn. A good quality mosquito repellent helps in decreasing the risk of vector-borne disease. Applying the insect repellent DEET to the skin and also using permethrin for clothes plays an important role in personal hygiene.
Home environment, personal hygiene, and clothing choice can also help reduce the risk of mosquito bites:
Encephalitis is the inflammation of brain caused mainly due to a viral infection. The affecting virus can enter your body through other infected human beings or through animals. Once inside the body, the virus starts showing the symptoms of the disease that are similar to common flu. As the disease progress, it leads to neurological symptoms like confusion, paralysis, hallucinations, lethargy, neck stiffness and pain, headache, photophobia, etc.
In extreme cases of encephalitis, the brain swells in the skull and puts downward pressure on the brain stem. The brain stem controls all the important functions, such as respiration and heartbeat. If the pressure becomes too much, these vital functions can stop leading to death.
Early and prompt treatment  of this disease can help in complete recovery and if time lapses in obtaining the treatment, person can suffer some loss in his motor or mental abilities. Personal hygiene and hygiene of your vicinity plays an important role in keeping this disease at bay.