What Is Encephalitis

Have you ever experienced a prolonged headache or other symptoms even after you got treated for an infection? Did you skip visiting the doctor and self-administered some painkillers to treat yourself? Not to alarm you, but you could have been experiencing symptoms of a rare condition called encephalitis

Encephalitis is a severe condition that results in swelling (inflammation) of the brain, due to viral or bacterial infections. Read on to understand what encephalitis is, its causes, its symptoms and how one could prevent it. 


The human brain is made up of different tissues that carry out various processes, from retaining memory to controlling the overall body. During these activities, the brain tissues become active and become prone to inflammation (swelling) due to infections. Encephalitis is primarily a viral infection of the brain tissues, which in turn causes the entire brain to swell. Encephalitis can also be caused due to bacterial or fungal infections, due to intake of certain medications or in a person with a weakened immune system.1

Encephalitis can affect all irrespective of age, but is more prevalent in older and younger individuals. In the UK, each year 4,000 people suffer from encephalitis due to its rarity. There are just a few viruses that may damage brain cells and enter the central nervous system (the brain and spinal cord). But the blood-brain barrier filters blood and keeps hazardous substances including viruses from reaching the brain. Due to this protective mechanism most of the time, infections caused by certain viruses will not result in encephalitis.2

One or more parts of the brain may become inflamed depending on how moderate or severe the infection is. A headache, a stiff neck, sensitivity to light, mental disorientation, and seizures might result from the swelling of the brain, which could be fatal if not diagnosed and treated at the right time.1,2 

Causes of encephalitis

Encephalitis is caused by a variety of factors such as viral or bacterial infections or other non-infectious causes. The precise origin of encephalitis is frequently unclear, however, certain instances such as an immune reaction, and genetic and environmental factors result in it. 

Some of the widely known causes of encephalitis are:1,3,4

  • Viral infections: This is the most common cause of encephalitis, with herpes simplex virus (HSV) and varicella-zoster virus (VZV- cause of shingles or chickenpox) being the most frequent viral causes. Other viruses that can cause encephalitis include the West Nile virus, enteroviruses, and measles virus
  • Bacterial infections: In rare cases, encephalitis can also be caused by bacterial infections, such as those caused by the bacteria that cause Lyme disease or Rocky Mountain spotted fever also known as tick-borne encephalitis
  • Autoimmune causes: When a person’s immune system mistakes the brain as a foreign object it tends to attack it, causing autoimmune encephalitis. Other autoimmune disorders, such as lupus or multiple sclerosis are also another cause
  • Other non-infectious causes: In some cases, encephalitis may develop as a result of a brain injury, such as from a stroke or traumatic injury. Certain reactions to medications or vaccines are also a cause

It's also important to keep in mind that various regions of the world have specific viruses and bacteria that are more frequently linked to encephalitis. While tick-borne encephalitis is more prevalent in Europe, in some parts of Asia encephalitis is caused due to Japanese encephalitis virus. As encephalitis is caused by different and complex causes, it is important to visit a doctor if you have any of the mentioned causes for timely treatment.3,4

Signs and symptoms of encephalitis

Encephalitis causes a range of symptoms ranging from physical to cognitive in nature. Encephalitis begins with flu-like symptoms or headaches and frequently progresses to an altered mental state and issues with thinking, remembering, and reasoning.5,6

Depending on the underlying cause and the severity, encephalitis symptoms can vary, however some frequent signs and symptoms include:4,5,6,7

  • Fever
  • Headache
  • Sensitivity to light or sound
  • Confusion or altered mental status: Encephalitis can cause changes in mental status, such as confusion, disorientation, or difficulty concentrating
  • Seizures: Seizures may occur in some people with encephalitis, particularly in cases caused by the herpes simplex virus
  • Muscle weakness or paralysis: In severe cases of encephalitis, muscle weakness or paralysis may occur, particularly in the arms or legs
  • Sensory changes: Encephalitis can cause changes in sensation, such as tingling, numbness, or a burning sensation
  • Vision or hearing changes: Encephalitis may cause vision or hearing changes, such as blurred vision or ringing in the ears
  • Personality or behaviour changes: Encephalitis can cause changes in personality or behaviour, such as irritability, aggression, or apathy

Encephalitis can have more significant side effects in extreme situations, including coma, brain damage, and even death. If you notice any of the following symptoms, it's crucial to contact a doctor very once, especially if you've recently been sick or have been exposed to ticks or mosquitoes in a region where encephalitis is known to occur.

Diagnosis of encephalitis

The diagnosis of encephalitis involves a combination of clinical testing, laboratory testing, and imaging studies to evaluate the symptoms, identify the underlying cause and determine how much the brain has inflamed.

The commonly used diagnostic methods in the evaluation of encephalitis are:4,5,6,7

  • Medical history and physical examination: The doctor will evaluate the symptoms, medical history, recent exposures to infectious agents, such as mosquitoes or tick bites and recent travel history
  • Blood tests: Blood tests are done to check for the presence of viruses or bacteria to evaluate current and previous infections. Blood tests may also be used to check for signs of inflammation or abnormalities in liver and kidney function
  • Imaging: The amount of brain inflammation may be assessed using imaging tests like computed tomography (CT) or magnetic resonance imaging (MRI), which can also be used to rule out other illnesses like brain tumours or abscesses that can produce symptoms that are similar to those of inflammation
  • Lumbar puncture: The procedure of a lumbar puncture, commonly referred to as a spinal tap, entails drawing cerebrospinal fluid (CSF) from the lower back. The transparent fluid called CSF, which surrounds the brain and spinal cord, can be examined for indications of infection or inflammation
  • Electroencephalogram (EEG): An EEG is a test that measures the electrical activity of the brain. It may be used to evaluate seizure activity or abnormal brain function in people with encephalitis

Further tests could be required once an encephalitis diagnosis has been obtained to determine the precise cause of the illness. Further blood tests, imaging analyses, or virus cultures of CSF or other bodily fluids may be required.

Management and treatment for encephalitis

The management and treatment of encephalitis depend on its cause and severity of it along with the patient’s overall health. In most cases, treatment involves supportive care to relieve symptoms and prevent complications, as well as antiviral or antibiotic medications to treat the underlying infection. Patients with encephalitis might need to stay in the ICU so that healthcare professionals can keep an eye out for seizures, brain swelling, respiratory failure, or changes in heart rhythm during the course of treatment.

Management and treatment strategies for encephalitis include:3,4,5,6,7

  • Antiviral or antibiotic medications: These medications are used to treat the underlying infection. For example, acyclovir is commonly used to treat encephalitis caused by the herpes simplex virus
  • Anti-seizure medication, in case of advanced encephalitis seizures might, is caused
  • Pain KIllers may be used to relieve headaches or reduce fever
  • Immunomodulatory therapy may be used to treat encephalitis caused by an autoimmune response
  • Fluids are given intravenously (IV) to keep you hydrated
  • Steroids are used to reduce brain inflammation
  • Breathing support, such as extra oxygen or a breathing machine (mechanical ventilation) is used in advanced cases

To avoid complications and promote recovery, encephalitis management and treatment require immediate medical intervention and constant monitoring. You must visit an emergency room right away if you are showing signs of encephalitis. 

Risk factors

Several factors can increase the risk of developing encephalitis:4,7

  • Age: Encephalitis can affect individuals of any age, but young children and older adults are more prone to develop it
  • Weakened immune system: Encephalitis risk is increased by immune system weakness brought on by underlying diseases like cancer or HIV/AIDS, as well as by immune system-suppressing drugs
  • Travel/exposure to parasites: The risk of certain types of encephalitis, such as West Nile virus encephalitis or Japanese encephalitis, is higher in certain geographic locations where the virus is prevalent. Exposure to infectious agents, such as mosquitoes or tick bites, or contact with animals that carry infectious agents, such as bats, can increase the risk of developing encephalitis
  • Previous infections: Some infections, such as herpes simplex virus or Epstein-Barr virus, can cause encephalitis or increase the risk of developing encephalitis in the future
  • Genetic factors: Certain genetic/hereditary factors are seen to increase the risk of developing encephalitis or affect the severity of the symptoms
  • It is important to remember that while certain factors can increase the risk of developing encephalitis, anyone can develop the condition. If you have concerns about your risk of developing encephalitis, speak with your GP to discuss preventive measures and early detection strategies


Depending on the severity of the inflammation and the underlying cause of the infection, encephalitis is a dangerous illness that can lead to a variety of problems.

Some of the common complications of encephalitis include:4,5,6,7

  • Seizures: The inflammation in the brain caused by encephalitis can disrupt the electrical activity of the brain, which can result in seizures
  • Memory loss and cognitive impairment: Encephalitis can result in memory loss and cognitive dysfunction, including problems with focus, attention, and decision-making
  • Behavioural changes: Personality changes, irritability, mood swings, and other behavioural changes can be brought on by encephalitis
  • Movement disorders: Encephalitis can cause movement disorders, such as tremors, rigidity, and involuntary movements
  • Speech problems: Speech and language issues, such as trouble with pronunciation, understanding, and expression, can be brought on by encephalitis
  • Coma: In severe cases, encephalitis can cause a coma, which is a state of unconsciousness
  • Brain damage: Prolonged inflammation in the brain can cause permanent brain damage, leading to long-term disability and cognitive deficits

In rare cases, encephalitis can be life-threatening, especially in individuals with weakened immune systems or severe neurological symptoms. It is important to seek medical attention promptly if you suspect you have encephalitis or are experiencing any symptoms of neurological impairment, as early as possible. 


Can encephalitis be prevented?

Yes, by reducing exposure to mosquitoes, maintaining excellent hygiene, and receiving vaccinations for specific viruses including measles, mumps, and rubella can all help prevent encephalitis.7

How common is encephalitis?

Encephalitis is a rare condition, with an estimated incidence of 4000 cases per year.2

When should I see a doctor?

You should visit a doctor right away if you suffer any encephalitis symptoms, including fever, headache, disorientation, seizures, or weakness. Early diagnosis and action can reduce complications and enhance recovery.5


A rare yet deadly disorder called encephalitis can inflame the brain and have life-threatening side effects. Many things, including bacterial and viral infections, autoimmune disorders, and environmental pollutants, contribute to its development. Fever, headache, disorientation, convulsions, and behavioural abnormalities are just a few of the signs of encephalitis. Early detection and intervention are essential for reducing problems and achieving better results. Although encephalitis is uncommon in the UK, it is crucial to visit a doctor as soon as possible if you think you may have it or if you show any signs and symptoms.


  1. Alam AM, Easton A, Nicholson TR, Irani SR, Davies NW, Solomon T, Michael BD. Encephalitis: diagnosis, management and recent advances in the field of encephalitides. Postgraduate medical journal. 2022 Jun 22.
  2. bgdteam. Encephalitis | fact sheet | health information | brain & spine foundation [Internet]. 2022. Available from: https://www.brainandspine.org.uk/health-information/fact-sheets/encephalitis/ 
  3. Roos KL. Encephalitis. Neurologic clinics. 1999 Nov 1;17(4):813-33.
  4. Stone MJ, Hawkins CP. A medical overview of encephalitis. Neuropsychological rehabilitation. 2007 Aug 1;17(4-5):429-49.
  5. Encephalitis [Internet]. nhs.uk. 2017. Available from: https://www.nhs.uk/conditions/encephalitis/ 
  6. Encephalitis [Internet]. 2021. Available from: https://www.hopkinsmedicine.org/health/conditions-and-diseases/encephalitis 
  7. Encephalitis: Causes, risk factors, symptoms, treatment [Internet]. Cleveland Clinic. Available from: https://my.clevelandclinic.org/health/diseases/6058-encephalitis
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Jeffy Joseph Vinohar

MSc. Oncology, University of Nottingham, England

Jeffy is an aspiring academic scientist with a bachelors in Biomedical sciences, Biotechnology with a keen interest in cancer studies. During her masters she aimed to learn more about making healthcare accessible and solutions to reduce healthcare inequalities in the field of oncology.
She currently interested in paediatric neuro-oncology and developing less invasive therapeutics for it by obtaining a PhD in coming years, while being involved with simplifying scientific research into health awareness articles.

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