Encephalitis is brain inflammation (swelling). Causes include viral infections, infections from insect bites or an autoimmune reaction that affects your brain. It can be life-threatening or cause long-term complications. Treatment varies, but most people require hospitalization so they can receive intensive treatment, including life support.
Encephalitis is a rare, serious condition that causes inflammation in your brain so that it swells. It can occur as a result of an infection or an autoimmune process. Encephalitis can be life-threatening, regardless of the cause, and can cause long-term complications and medical issues. Treatment varies depending on the cause, but most people with encephalitis require hospitalization so they can receive intensive treatment, including life support measures.
Condition types include infective encephalitis and autoimmune encephalitis. Infective encephalitis includes:
In autoimmune encephalitis, your immune system mistakenly attacks your brain, causing inflammation that may affect how your brain works. This sometimes happens to people with cancer. Healthcare providers call this paraneoplastic syndrome.
Advertisement
Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy
Symptoms vary depending on the type of encephalitis. Encephalitis from infections typically develops more quickly than autoimmune encephalitis. Early warning signs of infective encephalitis include:
Autoimmune encephalitis develops more slowly and causes neurological symptoms. These symptoms can be life-threatening if you don’t get medical help right away:
Infective and autoimmune encephalitis may be life-threatening. Call 911 (or your local emergency services number) if you have these symptoms or are with someone who has these symptoms.
The most common cause is when certain viruses affect your brain. That usually happens if you have the herpes simplex virus (HSV). But you can develop encephalitis if you have certain infectious diseases or other viruses.
Infectious disease viruses that cause encephalitis include:
Other viruses that cause the condition include:
Viruses spread by insects include:
Anyone can get encephalitis, but it typically affects people who have certain viral infections or are exposed to insect-borne viruses.
Insect-borne viruses are regional, meaning you’re more likely to be exposed to certain insects — and their bites — depending on where you live. Likewise, someone who spends time outside, particularly near places with standing water, has an increased risk of being bitten by mosquitos carrying viruses that may cause encephalitis.
Advertisement
Encephalitis may cause neurologic issues, some of which may require ongoing medical treatment and support. Complications may include:
Healthcare providers will do a physical examination. They’ll ask about your symptoms, including how long you’ve had them. They may do the following tests:
Advertisement
Healthcare providers treat the condition’s underlying cause and symptoms. Most people with encephalitis are treated in the hospital so providers can monitor their symptoms and move quickly if symptoms get worse. Treatments include:
Viral infections and viruses carried by insects are common encephalitis causes. You may be able to reduce your risk by keeping vaccinations up to date as needed and protecting yourself from mosquito bites.
Make sure you have current vaccinations against chickenpox, measles, mumps and rubella. Most people receive MMR vaccinations as children. These are one-and-done vaccinations; people don’t need to update them. But this combination vaccine wasn’t introduced until 1971. If you were born before then, ask your healthcare provider what vaccinations make sense.
Infected mosquitoes can pose a serious health risk. You can prevent mosquito bites by:
You may have encephalitis symptoms for a few days up to two or three months. It can take an additional two or three months to completely recover from the condition.
Medication to treat underlying conditions, like viruses, may cure encephalitis. In some cases, however, encephalitis may cause long-term issues that require ongoing medical care. For example, people may have ongoing issues with behavior, memory loss or speech.
That depends on their situation. While most people with encephalitis recover, the condition can be life-threatening. One study showed 5% of people died while in the hospital for encephalitis treatment. In general, how long you live after recovering from encephalitis depends on factors like:
If you have encephalitis or care for someone who does, ask a healthcare provider what to expect.
It takes time for your brain to heal from encephalitis, so recovery is more of a marathon than a sprint. Here are some suggestions that may help you along the road to recovery:
If you have encephalitis, ask your provider about changes that may mean your condition is getting worse. And go to the emergency room anytime you have symptoms like confusion, noticeable personality changes, speech issues or weakness, or you can’t move your arms or legs.
A note from Cleveland Clinic
Encephalitis is a serious disease that can have long-term consequences. It can take months or years for you to fully recover from the condition. Unlike injuries or illnesses that affect your body, you can’t see or feel your brain beginning to heal. People may assume you’re completely recovered when you’re still working through issues, from ongoing fatigue to neurological challenges. If that’s your situation, take time to explain how encephalitis continues to affect you.
Last reviewed on 12/18/2023.
Learn more about the Health Library and our editorial process.
Advertisement
Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy