Encephalitis

Overview

Encephalitis (en-sef-uh-LYE-tis) is inflammation (swelling) of the brain. It is usually caused by an infection, most often a virus, or by the immune system mistakenly attacking the brain.

No, encephalitis is rare. It affects about 1 in 100,000 people in the UK each year.

Anyone can get encephalitis, but it is most common in young children, older adults, and people with weakened immune systems.

Symptoms

Common symptoms

• Fever (high temperature)
• Severe headache
• Confusion or disorientation
• Stiff neck (difficulty touching chin to chest)
• Sensitivity to light (photophobia)
• Seizures (fits)
• Nausea and vomiting
• Extreme tiredness (fatigue)

Symptoms in children

• Irritability or crying more than usual
• Poor feeding or not wanting to eat
• Vomiting
• Unusual sleepiness or difficulty waking up
• Stiff body or floppy limbs
• Bulging soft spot on the head (in babies)

Symptoms in older adults

• Sudden confusion or memory problems
• Personality changes (e.g., becoming withdrawn or agitated)
• Weakness in one side of the body
• Difficulty speaking or understanding speech

Causes

Main causes

• Viral infections – the most common cause. Viruses such as herpes simplex (cold sore virus), varicella zoster (chickenpox), measles, mumps, rubella, and some mosquito-borne viruses (like West Nile virus).
• Autoimmune reactions – when the body's immune system attacks healthy brain tissue by mistake (autoimmune encephalitis).
• Bacterial infections – rare but can happen, for example from untreated sinusitis or meningitis.

Risk factors

• Being very young (infants and children under 5) or older than 65
• Having a weakened immune system (e.g., due to HIV, chemotherapy, or organ transplant)
• Living in or traveling to areas where mosquito-borne viruses are common
• Not being vaccinated against preventable diseases like measles, mumps, rubella, and chickenpox

When to see a doctor

See a doctor urgently if:

• You or your child have a severe headache with fever, or a fever that won't come down.
• You or your child seem confused, disoriented, or act very differently than usual.
• You or your child have a seizure (fit) for the first time.
• A stiff neck with fever and headache.

Book a routine appointment if:

• You have a persistent headache that lasts more than 3 days despite rest and over-the-counter pain relief.
• You have a mild fever with other symptoms like fatigue or body aches that don't improve.
• You are worried about any unusual symptoms after a viral illness.

Diagnosis

A doctor will start by asking about your symptoms, recent infections, and travel history, and perform a neurological exam (testing reflexes, coordination, and mental state). If encephalitis is suspected, you will be admitted to hospital for further tests.

Tests that may be done

• Lumbar puncture (spinal tap) – a needle collects fluid from your lower back to look for signs of infection or inflammation.
• MRI scan – a detailed scan of the brain to check for swelling or changes.
• EEG (electroencephalogram) – electrodes on your scalp measure brain activity and can detect seizure-related patterns.
• Blood tests – to look for viruses, bacteria, or antibodies that can cause inflammation.
• In some cases, a brain biopsy (taking a small piece of brain tissue) may be needed if the cause is unclear.

What to expect at your appointment

You will likely be seen in hospital quickly. The lumbar puncture can be uncomfortable but is important for diagnosis. Results from some tests take a few days. The doctors will keep you comfortable and monitor you closely. You do not need to prepare in advance – the medical team will guide you.

Treatment

Treatment for encephalitis depends on the cause and is usually given in a hospital. The main goals are to control the swelling in the brain, treat the underlying cause, and support vital functions like breathing and blood pressure.

Self-care at home

• Rest as much as possible – your body needs energy to fight the inflammation.
• Drink plenty of fluids to stay hydrated, unless your doctor says otherwise.
• Take any prescribed medicines exactly as directed – do not skip doses.
• Avoid driving or operating machinery until your doctor says it is safe, especially if you have had seizures or confusion.

Medical treatments

Antiviral medicines are used if a virus is the cause. For autoimmune encephalitis, treatments that calm the immune system, such as corticosteroids or other immune-modulating therapies, may be given. Medications can also be used to control seizures, reduce fever, and manage pain. You may be given intravenous (IV) fluids and oxygen if needed. In severe cases, you might be cared for in an intensive care unit (ICU) where breathing, heart rate, and brain pressure can be closely watched.

When is surgery considered?

Very rarely, if swelling in the brain becomes dangerously high and medicines cannot control it, a surgeon may place a small drain or remove a piece of skull to relieve pressure. This is called decompressive craniectomy and is only done in life-threatening situations.

Living with this condition

Recovery from encephalitis can take weeks or months. You may feel very tired and need to take things slowly. It is important to follow up with your doctor, neurologist, and possibly a rehabilitation team. Give yourself time to heal and do not rush back to your full routine.

Lifestyle tips

• Get plenty of sleep – your brain repairs itself during rest.
• Avoid alcohol and recreational drugs, as they can interfere with recovery and medicines.
• Manage stress with relaxation techniques like deep breathing or gentle yoga.
• Stay connected with friends and family – they can support you emotionally.

Diet and exercise

Eat a balanced diet with plenty of fruits, vegetables, whole grains, and protein to support healing. Gentle exercise, like short walks, can help regain strength, but do not push yourself. Always check with your doctor before starting any new activity, especially if you have had seizures or balance problems.

Mental health and emotional wellbeing

Encephalitis can affect memory, concentration, mood, and personality. It is common to feel frustrated, anxious, or depressed. Talk to your doctor if you notice these changes – they can refer you to a neuropsychologist or counselor. You are not alone in this, and support can help you adjust.

Prevention

Not all cases of encephalitis can be prevented, but you can lower your risk by getting vaccinated and protecting yourself from infections.

Vaccines

Vaccines are available for some viruses that can cause encephalitis, such as measles, mumps, rubella (MMR vaccine), chickenpox, and influenza. Keeping up to date with recommended vaccinations helps protect you and your community.

Screening programmes

There is no routine screening for encephalitis. The best prevention is staying healthy, practicing good hygiene (like washing hands), and avoiding mosquito bites if you live in or travel to areas with mosquito-borne diseases.

Complications

If left untreated

• Permanent brain damage or cognitive impairment (memory loss, trouble concentrating)
• Epilepsy (ongoing seizures)
• Personality changes or severe mood swings
• Weakness or paralysis in parts of the body
• Coma or death

Long-term outlook

With prompt treatment, many people with encephalitis recover fully or have only mild lasting effects. Some may need ongoing rehabilitation, but significant improvement is often possible over time. Even if recovery is slow, there is hope and support available. The key is to get medical help quickly and to stick with your care plan.

Find support

International organisations

• The Encephalitis Society ↗

Local organisations

• NHS (UK) – Encephalitis ↗ · United Kingdom

Helplines

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