Definition and causes of Encephalitis
Encephalitis is an inflammation or irritation in the brain tissue caused by a virus or an immune reaction to certain infections elsewhere in the body such as chickenpox, flu, shingles or infectious mononucleosis. There is an incidence of around 1 new case per year in 50.000 persons in the western world.
If viral the most common is the different so-called enteroviruses (Coxsackie, ECHO and polio - the abbreviation of poliomyelitis), which can cause encephalitis, but the most serious form of the disease is caused by herpes simplex type 1. In earlier times measles was a common cause of encephalitis but after the introduction of MFR-vaccine this cause has virtually disappeared.
In some countries rabies transmitted to humans by the bite of infected animals, and Japanese encephalitis virus transmitted by mosquitoes are the major causes. Also tick bites might result in encephalitis and this form is called tick borne encephalitis which occurs more frequently in Eastern and Central Europe.
Symptoms of encephalitis
There can be very different symptoms, depending on what caused the condition. Frequent symptoms are:
The following are rarer but very serious symptoms:
Precautions and diagnosis
Any of the above symptoms require immediate medical attention. It is important to inform about travel and destinations during the period preceding the symptoms.
The medical examinations to determine a diagnosis involve taking a spinal cord fluid sample (lumbar puncture). Encephalitis will show as elevated white blood cell count. In addition, the brain's electrical activity may be checked with electrodes placed on the head (electroencefalogram, EEG) and/or by performing a CT or MRI scan. In some situations it is possible to detect the virus in the spinal cord fluid by special procedures.
Treatment of brain inflamation
When symptoms are serious treatment requires hospitalization. The treatment consists of alleviation of symptoms and treatment with an antiviral drug that directly attacks the virus. There is only one effective drug against herpes virus, but since this virus can cause very serious brain inflammation the drug is given with the slightest suspicion that the herpes virus is the cause. The specific antiviral drug is Aciclovir which comes in many different forms for different applications other than Encephalitis.
Prevention of encephalitis
There is a vaccine against Japanese encephalitis and tick borne encephalitis, so if you are traveling, it's a good idea to inquire if there is risk of being infected with one of these forms of encephalitis in the countries you plan to visit. More information about risk countries and vaccination can be found on the website of the Danish State Serum Institute which is published in many languages including English: http://www.ssi.dk/sw379.asp
Outlook and complications
The serious herpes induced encephalitis may end fatally, especially if not treated quickly. Many will continue to have severe symptoms after healing, such as those described above. There may also be problems with memory.