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Encephalitis refers to the inflammation of the brain. The inflammation leads to some symptoms like decreased or altered consciousness, confusion, headache, fever, and seizures. The causative agents of encephalitis are infectious, including bacteria, viruses, fungi, etc. It may also be caused by other inflammatory conditions like SLE, sarcoidosis, drugs, chemicals, etc. If treatment is started on time, the prognosis is good. Otherwise, it can lead to serious complications.

Types And Causes

Encephalitis can be caused by bacteria, viruses, fungi, parasites, and sometimes by certain drugs.

Viral encephalitis is among the commonest causes of encephalitis. Usually, the causative virus remains unknown. However, herpes simplex is the top among the most common. Some other viruses include rabies virus, varicella-zoster virus (VZV), cytomegalovirus (CMV), Epstein-Barr virus (EBV), measles virus, mumps virus, arboviral flavivirus (West Nile virus), bunyavirus, henipavirus, arenavirus (lymphocytic choriomeningitis virus), and reovirus (Colorado tick virus) infections.

Bacterial encephalitis and others: Some bacteria can also cause encephalitis. It can occur along with bacterial meningitis or alone as in syphilis and Lyme disease.

Few parasitic organisms can cause encephalitis in immunocompromised people, such as in malaria, toxoplasmosis, or primary amoebic meningoencephalitis.

Non- infectious Meningitis: This can be caused by other medical conditions such as lupus, a head injury, brain surgery, cancer, and certain medications.


In the United States, many cases of viral encephalitis are reported each year, which is just presumed to be less than the actual cases occurring. Herpes simplex encephalitis, which is common in Western countries is not much found in the USA, with an overall incidence of only 0.2 cases per 100,000, and 2-3 cases of neonatal HSV infection per 10,000 live births. Episodic encephalitis is most commonly caused by the arbovirus group. In countries like Japan, Southeast Asia, China, and India, the most common viral encephalitis is Japanese virus encephalitis (JE)

Encephalitis is more prevalent in extremes of ages, i.e., neonates and the elderly over 50 years of age. 

Risk Factors

Risk factors for encephalitis include:

·         Very old (more than 55 years of age) or very young (less than 5 years of age)

·         Some chronic conditions like Diabetes Mellitus, Chronic kidney Failure, Cystic Fibrosis, etc.

·         Immunosuppression, and HIV infection, increase the risk of opportunistic infections.

·         Alcoholics, IV drug abusers

·         Head injury or surgery

·         Living in regions with ticks and mosquitos 

Signs And Symptoms

The symptoms of encephalitis are described as follows:

·         Fever

·         Confusion

·         Altered consciousness

·         Nausea/vomiting

·         Headache

·         Increased sensitivity to light

·         Seizures

·         Stiff neck

·         Lethargy

·         Myalgia

·         Lymphadenopathy


If you feel you are experiencing the symptoms of encephalitis, do contact your health care provider for immediate assistance. The earlier, the better. The diagnosis is made on clinical symptoms and physical examination. Other tests are advised to confirm the diagnosis.

Blood tests: A complete blood count may show an increase in the number of WBCs. Some other parameters are also checked, like electrolytes, glucose, urea, and nitrogen. Blood culture: In this test, organisms are grown in the lab to check for the specific agent and the medicine it is sensitive to.

Lumbar Puncture: It is the procedure in which fluid in your brain and spinal cord, called cerebrospinal fluid, is taken out by a needle inserted in your vertebral column. On the basis of different parameters, the diagnosis is made like pressure, predominant cells, proteins, and glucose.

Imaging of the brain: CT or MRI scans of the brain may show swelling and can be used to determine complications and rule out other diagnoses.

Electroencephalogram: A paste is used to adhere electrodes to your scalp. It's a painless, non-invasive investigation. You may be requested to complete a certain activity. In some situations, the test is carried out while the patient sleeps. The electrodes will capture your brain's electrical activity. Changes in normal brain wave patterns may appear and can point toward encephalitis.

Brain biopsy: When the symptoms are not improving despite treatment, your doctor may suggest a brain biopsy in which a small sample of brain tissue is taken out and sent to the lab for testing. 

Differential Diagnosis

Following diseases may mimic the signs and symptoms of encephalitis;

·         Meningitis

·         Brain abscess

·         Subarachnoid hemorrhage

·         Cerebral malaria

·         Brain tumor

·         Leptospirosis

·         Subdural empyema


A cumulative approach is adopted to treat encephalitis, including antibiotics, antivirals, anti-inflammatory medications, Mannitol, glucocorticoids, anti-epileptics, supportive care, and rehabilitation.


Antibiotics and antivirals: The infectious types are treated with antibacterials and antivirals depending on the cause of the infection. The choice of medicines depends upon the results of the blood culture. However, a broad-spectrum antibiotic must be started without waiting for the result. The most commonly used antivirals are Acyclovir (Zovirax), Ganciclovir (Cytovene), Foscarnet (Foscavir)

Adjunctive medicines: These include anti-inflammatory drugs to control pain and fever,e.g., acetaminophen, ibuprofen, and naproxen sodium. Steroids may be used to treat and prevent complications. Other medicines may include anti-epileptics (phenytoin) and mannitol.

Supportive care: Bed rest and IV fluids are very important. Patients with breathing problems can be provided breathing assistance.

Follow-up therapy: A range of complications may occur that would require rehabilitation therapies to improve the symptoms. These may include; physiotherapy, speech therapy, occupational therapy, and psychotherapy. 


The outcome is dependent on the type of infectious agent and the presence of some poor prognostic factors like brain edema or swelling at the beginning of the disease. People who are immunocompromised, are in extremes of ages, and have previous neurological illnesses may have a complicated condition. Some symptoms may last long like fatigue, weakness, lack of muscle coordination, personality changes, memory problems, hearing or vision defects, and Speech impairment.  Sometimes patients have complications like brain abscesses, sinuses, seizures, shock, and death.


Encephalitis can be prevented by;

·         Taking care of basic hygiene like washing hands, keeping things clean, and discouraging sharing toothbrushes, towels, etc.

·         Take a healthy and clean diet with essential vitamins and minerals.

·         Covering of mouth during sneezing and coughing.

·         Cover yourself while you are in mosquitos or ticks prevalent areas and apply mosquito repellent.

·         Vaccinations: Many vaccinations have been used for the prevention of bacterial agents like Haemophilus influenza type b (Hib) vaccine., Pneumococcal polysaccharide vaccine (PPSV23). Pneumococcal conjugate vaccine (PCV13), Meningococcal conjugate vaccine, rabies (virus) vaccine.

·         You should get vaccinated for the Japanese encephalitis virus if traveling to Japan, India, or China.

Our clinical experts continually monitor the health and medical content posted on CURA4U, and we update our blogs and articles when new information becomes available. Last reviewed by Dr.Saad Zia on May 17, 2023.


Encephalitis - NHS (www.nhs.uk)


Encephalitis | National Institute of Neurological Disorders and Stroke (nih.gov)


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