What is encephalitis?
Encephalitis means inflammation of the brain. Fever, headache, and joint pain are often experienced in the early stages of encephalitis. Other severe symptoms may develop over some days or hours. They include personality changes, seizures, disorientation, confusion, or drowsiness.
Some causes of encephalitis are infections and the way the body’s immune system reacts to certain changes such as malignant tumors or a delayed reaction to previous infections. When inflammation remains for many months, chronic encephalitis may develop. However, there may be unknown causes of encephalitis sometimes. In some cases, HIV may cause encephalitis. If encephalitis occurs, then treatment needs to be done in a hospital, particularly in the intensive care unit. It can take many months to recover and lasting complications are possible such as memory loss.
Although brain inflammation is not contagious, the viruses that cause encephalitis can be. When the same virus present in the person with encephalitis enters into the body of another person, then it does not necessarily mean that the other person will also get the disease.
Two Types of Encephalitis
- Primary Encephalitis - This type of encephalitis develops when a virus or another infectious agent directly infects the brain. It can be localized to one region or may be widespread. A primary infection may be a result of a reactivated virus, which became inactive after a past illness.
- Secondary or Post-Infectious Encephalitis - A secondary infection may occur in response to an infection occurring elsewhere in the body, in reaction to a defensive immune system. Instead of only attacking the infection-causing cells, the body's immune system mistakenly attacks the healthy cells of the brain. Secondary encephalitis usually occurs 2-3 weeks after the initial infection. This type of encephalitis may rarely occur due to live virus vaccinations.
Causes of Encephalitis
A variety of viruses, bacteria, and other organisms can cause encephalitis. The most common causes of encephalitis in the United States are viral infections caused by enterovirus, arbovirus and herpes simplex virus. Once in the body, these viruses can cause cold-like symptoms or mild illness. However, when they are carried by the nervous system, they can spread to the bloodstream. By multiplying in the nervous system, they may cause infection and inflammation of the brain.
- Arboviruses and Bacteria - Arboviruses are a group of viruses, which are spread through the bites of bloodsucking insects such as mosquitoes and ticks. They can cause Powassan encephalitis, West Nile encephalitis, Saint Louis encephalitis, and Eastern equine encephalitis viruses. Lyme disease and Rocky Mountain spotted fever are also caused by tick bites, which carry harmful bacteria. Similarly, the rabies virus can also be transmitted by the bite of infected animals.
- Enteroviruses - These viruses are spread by direct hand-to-mouth contact. They are very common viruses, which can be transmitted through contact with fecal matter of an infected person or by coughing. Usually, upper respiratory symptoms or flu-like symptoms are caused by enterovirus infections.
- Herpesviruses - These viruses can be transmitted through sexual contact, direct contact with a herpes rash or sores, and by close contact with an infected individual. They include varicella-zoster virus, Epstein-Barr virus, cytomegalovirus, and herpes simplex virus types 1 and 2. Acyclovir is effective in suspected herpes virus cases.
Less Common Causes of Encephalitis
Unless a person has a weakened immune system, such infections usually do not cause disease. However, in people who are immunocompromised, parasitic infections such as toxoplasmosis and amoebiasis are more likely to occur. Syphilis and tuberculosis are other less common bacterial causes of encephalitis.
Other causes of encephalitis include:
- Certain types of cancer
- Autoimmune disorders
- Reaction to certain vaccines
Although the exact cause of encephalitis is still unknown, most diagnosed cases are due to viral infections. The causes of encephalitis are noninflammatory conditions and bacterial infections. Laboratory diagnosis is often difficult since irreversible complications are often led by brain biopsy. A viral infection diagnosis is difficult to evaluate with routine radiological studies and blood examination.
The most common causes of brain inflammation are viral infections. Following bacterial meningitis, the complications observed are paralysis, hearing loss, stroke, and brain damage. Most people recover without having any complications after viral or bacterial infections caused by enteroviruses, varicella-zoster, mumps, or influenza. Severe infection of the meninges and the brain may cause complications after a bacterial infection, although chances of this infection are rare.
Cryptococcus neoformans causes a fungal infection in the brain including the surrounding meninges. Fungal encephalitis is often associated with patients who have AIDS and those who have terminal cancer. Noninfectious inflammatory conditions caused by trauma and autoinflammatory diseases can also cause encephalitis.
Childhood infections may also cause secondary encephalitis. They include some of the common childhood infections such as rubeola (measles), mumps, and rubella (German measles). However, these diseases have now become rare due to the development of vaccines.
Encephalitis can affect anyone at any age. However, there are certain factors that may increase an individual’s risk of developing the condition. Risk factors include:
- Age - Generally, young children and the elderly have an increased risk of developing common types of viral encephalitis.
- Low Immune System - Individuals who are taking immunosuppressant drugs, those who have HIV/AIDS, or other medical conditions that impair their immune system are usually at a greater risk of having encephalitis.
- Geographic Location - Tick-borne or mosquito-borne viruses are endemic in certain regions.
- Seasonal Factor - Vector-borne diseases (through tick or mosquito bites) tend to commonly occur during summer in many US areas.
Some viral infections such as measles, mumps, and chickenpox can be prevented through childhood vaccinations. Avoid being outdoors at dawn and dusk since most mosquitoes are active during these times. When outdoors, you can wear long sleeve shirts and long pants along with the application of an insect repellent. Moreover, always drain standing water.
Avoid direct contact with an infected person and practice good handwashing habits, especially before and after meals and after using the toilet. Avoid sharing eating utensils, unwashed drinking glasses, or personal items such as lip balms and toothbrushes.
Keep your family's vaccination updated, especially before traveling. Speak with the doctor regarding vaccinations for specific destinations.