Encephalitis is an inflammation of the brain. Most often, it is caused by one of several different viruses. The most common are the herpes viruses, childhood viruses such as measles, and viruses you get through a mosquito bite.

There are two types of encephalitis -- primary and secondary. In primary encephalitis, a virus attacks the brain and spinal cord directly. In secondary or postinfectious encephalitis, the virus invades another part of your body and travels to your brain. The virus causes inflammation of the nerve cells (encephalitis) or the surrounding membranes (meningitis). Encephalitis is different from meningitis, but these two brain infections often happen together.

Most cases of encephalitis are mild and do not last long. However, in some cases encephalitis can be life-threatening. Each year, several thousand cases of encephalitis are reported each year in the United States.

• Flu-like symptoms are common, such as fever, sore throat, cough, and malaise.
• If the person has meningitis and encephalitis, he or she may have a headache, stiff neck, vomiting, and be bothered by light.
• People with severe encephalitis usually have some change in consciousness, ranging from mild confusion to coma. They will often be disoriented and delusional with possible hallucinations, agitation, and personality changes.
• Other signs and symptoms of encephalitis depend on which area of the brain is most affected. These may include trouble using or understanding words or coordinating voluntary muscle movements, muscle weakness or partial paralysis on one side of the body, uncontrollable tremors or movements, seizures, and not being able to regulate body temperature.
• Infants may have bulging in the fontanels or soft spots on the skull.

Arboviruses, or viruses carried by insects, are some of the most common causes of viral encephalitis. Some of the major arboviruses carried by mosquitoes include:

• Eastern equine encephalitis -- This infection is rare, with only a few cases reported each year. However, about half the people who have severe symptoms die or have permanent brain damage.
• La Crosse encephalitis -- usually affects children under 16 years of age in the upper Midwestern United States. It is rarely fatal.
• St. Louis encephalitis -- People in rural Midwestern and southern United States are most affected. Many people have mild symptoms, although symptoms can be severe in people over age 60. Up to 30% of infected seniors die of the condition.
• West Nile encephalitis -- Primarily affects people in Africa, Europe, the Middle East, North America, and West Asia. Most cases are mild. Symptoms are most severe in older adults and people with weakened immune systems, and it can be fatal for them.
• Western equine encephalitis -- Affects people in North Central and South America. No cases have occurred in the United States since 1999. It usually causes a mild infection, except in children under 1 year of age, who can have permanent brain damage.

Other viruses that commonly cause viral encephalitis include:

• Herpes simplex virus type 1 (HSV-1), which is responsible for cold sores
• HSV-2, which is responsible for genital herpes
• Varicella zoster virus, which causes chicken pox and shingles
• Epstein-Barr virus, which causes mononucleosis
• Childhood viruses that can cause encephalitis include:
• Measles (rubeola), German measles (rubella), and Mumps

Not all cases of encephalitis are caused by viruses. Some other causes of encephalitis include:

• Bacteria
• Fungus
• Parasite
• Noninfectious causes, such as allergic reactions or toxins

The following factors may increase your risk of becoming infected with viral encephalitis:

• Being very young or an older adult
• Being exposed to mosquitoes or ticks
• Having a weakened immune system
• Not being vaccinated against measles, mumps, and rubella
• Traveling to areas where viral encephalitis is common

Encephalitis is a serious condition, so you should see a doctor if you or your child start having symptoms. You are usually diagnosed and treated in a hospital at first. After doing a physical exam, a doctor may take the following steps to diagnose the condition:

• Blood test -- finds viruses in the blood
• Spinal tap (lumbar puncture) -- finds viruses in the fluid around the brain and spinal cord
• Brain imaging -- magnetic resonance imaging (MRI) and computerized tomography (CT) scan see whether swelling is present in the brain
• Electroencephalogram (EEG) -- finds abnormal brain waves

The best way to prevent encephalitis is to avoid getting viruses that cause it:

• Protect yourself from mosquitoes. Use insect repellent and wear long pants and long sleeves. The most effective bug sprays contain DEET or Picaridin. Do not apply insect repellent to children under 2 years of age.
• Make sure your child is vaccinated against diseases such as the measles, mumps, and rubella (MMR).
• Eating a healthy diet can help keep your immune system healthy, but won't necessarily protect against illness.

Viral encephalitis is a serious medical condition. Although there are no specific medications to treat it, people with symptoms are often given the antiviral medication acyclovir (Zovirax). It works against herpes simplex and varicella-zoster viruses.

Studies investigating complementary and alternative therapies for the treatment of encephalitis are lacking, however, some studies indicate that scalp acupuncture, along with the right medication, may help the healing process.

Treatment includes careful observation and rest, proper nutrition, and fluids, to allow the body to fight the infection. You should always see your doctor if you have symptoms of encephalitis. Do not try to treat it yourself.

Always tell your health care provider about the herbs and supplements you are using or considering using, as some supplements may interfere with other medicines.

Medications

Medications used to treat viral encephalitis include:

• Antiviral medicines, if a virus caused the infection
• Antibiotics, if bacteria are the cause
• Antiseizure medicines to prevent seizures
• Steroids to reduce brain swelling
• Sedatives for irritability or restlessness
• Acetaminophen for fever and headache

Nutrition and Dietary Supplements

There aren't any vitamins or supplements that relieve the symptoms of encephalitis, however, following these tips may help your overall health as you recover:

• Eat a variety of fruits and vegetables. Plant foods are high in antioxidants.
• Avoid refined foods, such as white breads, pastas, and especially sugar.
• Use healthy oils in foods, such as olive oil or vegetable oil.
• Avoid caffeine, alcohol, and tobacco.
• Drink 6 to 8 glasses of filtered water daily.

These supplements may also help improve your overall health:

• Omega-3 fatty acids, such as fish oil, 1 to 3 times daily, to help reduce inflammation and boost the immune system. Fish oil may increase the risk of bleeding, especially if you take blood-thinners, such as warfarin (Coumadin), clopidogrel (Plavix), or aspirin.
• Probiotic supplement (containing Lactobacillus acidophilus), 5 to 10 billion CFUs (colony forming units) a day, for digestive and immune system health. If you are taking antibiotics, probiotics may help you avoid some side effects, such as diarrhea. People with autoimmune diseases, such as rheumatoid arthritis or psoriasis, or those with weakened immune systems should ask their doctor before taking probiotics.

Herbs

Herbs may strengthen and tone the body's systems. As with any therapy, you should work with your health care provider to diagnose your problem before starting any treatment. You may use herbs as dried extracts (capsules, powders, teas), glycerites (glycerine extracts), or tinctures (alcohol extracts). Unless otherwise indicated, you should make teas with 1 tsp. herb per cup of hot water. Steep covered 5 to 10 minutes for leaf or flowers, and 10 to 20 minutes for roots. Drink 2 to 4 cups per day.

No herbs have been shown to help treat encephalitis. These herbs may help strengthen the immune system. Ask your doctor before taking them:

• Green tea (Camellia sinensis) standardized extract, 250 to 500 mg daily. This antioxidant may help reduce inflammation and boost the immune system. Use caffeine-free products. You may also make teas from the leaf of this herb.
• Cat's claw (Uncaria tomentosa) standardized extract, 20 mg, 3 times per day. This herb may reduce inflammation and fight viruses. Cat's claw can interfere with some medications, so ask your doctor before taking it. People with leukemia or autoimmune diseases, such as rheumatoid arthritis or lupus, should not take cat’s claw.
• Garlic (Allium sativum), standardized extract, 400 mg, 2 to 3 times daily, to boost the immune system. Garlic can increase the risk of bleeding, especially if you take blood-thinners such as warfarin (Coumadin), clopidogrel (Plavix), and aspirin. It can also interfere with a number of medications. People with ulcers should ask their doctor before taking garlic.
• Astragalus (Astragalus membranaceus) to boost the immune system and fight viruses. Astragalus interacts with lithium and maybe with some other medications, as well. People with autoimmune diseases, such as rheumatoid arthritis or psoriasis, should ask their doctor before taking astragalus.
• Elderberry (Sambucus nigra) to boost the immune system and fight viruses. People with autoimmune diseases should ask their doctor before taking elderberry.

Pregnancy

Most cases of encephalitis in newborns are caused by when the baby passes through the birth canal of a mother who is infected with herpes simplex virus 2 (HSV-2). This infection in newborns is often severe and fatal. Pregnant women with a history of HSV-2 infection may be advised to have a cesarean section, even if there is no sign of an active infection.

Prognosis and Complications

Full recovery from encephalitis can take weeks or months. People recovering from serious cases may have complications ranging from fatigue and trouble concentrating to tremors and personality changes.

The most severe problems from encephalitis come from the destruction of nerve cells in the brain. Complications depend on the person's immune system -- whether it is healthy or weak -- and what infection caused the encephalitis. For example, many of those infected with Eastern equine encephalitis and St. Louis encephalitis have permanent brain damage, including problems with memory, speech, vision, hearing, muscle control, and sensation, and a low survival rate. Those infected with Epstein-Barr or varicella zoster rarely have any serious complications.

Most cases of encephalitis are mild and people make a full recovery.

Aksamit AJ. Encephalitis. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 383.

Ansary J, Forbes-Hernández TY, Gil E, et al. Potential health benefit of garlic based on human intervention studies: a brief overview. Antioxidants (Basel). 2020 ;9(7):619. PMID: 32679751 pmc.ncbi.nlm.nih.gov/articles/PMC7402177/.

Beckham JD. Arboviruses causing fever, rash, and neurologic syndromes. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 352.

Centers for Disease Control and Prevention website . About Eastern Equine encephalitis. www.cdc.gov/eastern-equine-encephalitis/about/index.html. Updated May 15, 2024. Accessed May 16, 2025.

Centers for Disease Control and Prevention website. About La Crosse. www.cdc.gov/la-crosse-encephalitis/about/index.html. Updated May 15, 2024. Accessed May 16, 2025.

Centers for Disease Control and Prevention website. Japanese encephalitis virus. preventing Japanese encephalitis. www.cdc.gov/japanese-encephalitis/prevention/index.html. Updated May 19, 2024. Accessed May 19, 2025.

Centers for Disease Control and Prevention website. St. Louis encephalitis: symptoms, diagnosis, and treatment. www.cdc.gov/sle/symptoms-diagnosis-treatment/index.html. Updated May 15, 2024. Accessed May 16, 2025.

Hasbun R. Meningitis and encephalitis. In: Winn HR, ed. Youmans and Winn Neurological Surgery. 8th ed. Philadelphia, PA: Elsevier; 2023:chap 57.

National Center for Complementary and Integrative Health website. Astragalus. www.nccih.nih.gov/health/astragalus. Updated May 2025. Accessed June 16, 2025.

National Center for Complementary and Integrative Health website. Cat's claw. www.nccih.nih.gov/health/cats-claw. Updated November 2024. Accessed June 16, 2025.

National Center for Complementary and Integrative Health website. Elderberry. www.nccih.nih.gov/health/elderberry. Updated November 2024. Accessed June 16, 2025.

National Center for Complementary and Integrative Health website. Garlic. www.nccih.nih.gov/health/garlic. Updated February 2025. Accessed June 16, 2025.

Schnapp BH, Jewell C. Central nervous system infections. In: Walls RM, ed. Rosen's Emergency Medicine: Concepts and Clinical Practice. 10th ed. Philadelphia, PA: Elsevier; 2023:chap 9.

Thomas SJ, Endy TP, Rothman AL, Barrett AD. Flaviviruses (dengue, yellow fever, Japanese encephalitis, West Nile encephalitis, Usutu encephalitis, St. Louis encephalitis, tick-borne encephalitis, Kyasanur forest disease, Alkhurma hemorrhagic fever, Zika). In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 153.

Marcdante KJ, Kliegman RM, Schuh AM. Encephalitis. In: Marcdante KJ, Kliegman RM, Schuh AM, eds. Nelson Essentials of Pediatrics. 9th ed. Philadelphia, PA: Elsevier; 2023:chap 101.

Mi Y, Guo Y, Luo X, Bai Y, Chen H, Wang M, Wang Y, Guo J. Natural products and derivatives as Japanese encephalitis virus antivirals. Pathog Dis. 2024;82:ftae022. PMID: 39317665 pmc.ncbi.nlm.nih.gov/articles/PMC11556344/.

National Institute of Neurological Disorders and Stroke. Encephalitis. www.ninds.nih.gov/health-information/disorders/encephalitis. Updated November 26, 2024. Accessed May 16, 2025.

Prasanth MI, Sivamaruthi BS, Chaiyasut C, Tencomnao T. A review of the role of green tea (Camellia sinensis) in antiphotoaging, stress resistance, neuroprotection, and autophagy. Nutrients. 2019 ;11(2):474. PMID: 30813433 pmc.ncbi.nlm.nih.gov/articles/PMC6412948/.

U.S. Department of Health and Human Services. National Center for Complementary and Integrative Health website. Cat's claw. www.nccih.nih.gov/health/cats-claw. Updated November 2024. Accessed May 19, 2025.

Wieland LS, Piechotta V, Feinberg T, et al. Elderberry for prevention and treatment of viral respiratory illnesses: a systematic review. BMC Complement Med Ther. 2021;21(1):112. PMID: 33827515 pmc.ncbi.nlm.nih.gov/articles/PMC8026097/.

Williams JA, Long SY, Zeng X, et al. Eastern equine encephalitis virus rapidly infects and disseminates in the brain and spinal cord of cynomolgus macaques following aerosol challenge. PLoS Negl Trop Dis. 2022;16(5):e0010081. PMID: 35533188 pmc.ncbi.nlm.nih.gov/articles/PMC9084534/.

Wood GK, Babar R, Ellul MA, et al. Acute seizure risk in patients with encephalitis: development and validation of clinical prediction models from two independent prospective multicentre cohorts. BMJ Neurol Open. 2022 ;4(2):e000323. PMID: 36110928 pmc.ncbi.nlm.nih.gov/articles/PMC9445799/.