Encephalitis – Causes, Signs and symptoms


Reviewed By:
Timothy Yarboro, M.D.


Encephalitis is an inflammation of the brain. People with encephalitis usually experience mild symptoms, if any. However, encephalitis can be severe or even fatal in some circumstances.

Encephalitis is acquired by either infection of the brain and spinal cord (primary encephalitis) or as a result of an infection elsewhere in the body that spreads to the brain (secondary or postinfectious encephalitis). Primary encephalitis tends to be more dangerous, although it is much less common than secondary encephalitis. In general, encephalitis is rare in the United States.

Many viruses may cause encephalitis, including several viruses in the herpes group such as herpes simplex virus 1 (HSV-1), herpes simplex virus 2 (HSV-2) and chickenpox. Other viruses that can cause encephalitis are enteroviruses, which are usually found in human intestines and arboviruses, which are transmitted by infected arthropods (insects and insect-like animals with a hard outer skeleton and jointed limbs), usually mosquitoes.

Of the types of encephalitis caused by arboviruses, Japanese encephalitis is the most common form of the disease worldwide. While it is the cause of thousands of cases in Asia each year, it is rare in the United States. Occasionally there are notable outbreaks of diseases caused by arboviruses such as the West Nile virus or eastern equine encephalitis. In addition, bacteria, fungi and parasites may also cause encephalitis if they invade the brain.

Encephalitis frequently occurs with meningitis. In these cases, inflammation affects the meninges, the membranes that line the brain and spinal cord. Both diseases have similar routes to the body and similar symptoms.

 Encephalitis mainly affects children, elderly people, individuals with weakened immune systems (e.g., cancer or HIV/ AIDS patients) or people who reside in areas with high mosquito populations.

Pain and discomfort (e.g., headache, neck or back stiffness) are common symptoms of encephalitis. However, the type and severity of symptoms can vary greatly among individuals.

Methods for diagnosing encephalitis include spinal tap, blood tests and brain imaging. Depending on the severity of the disease in the patient, treatment options may involve rest, physical therapy, speech therapy, antibiotics and anticonvulsant (seizure) medications. Avoiding situations in which the germs that cause encephalitis are transmitted can help prevent the condition. This includes taking the appropriate precautions against sexually transmitted diseases and limiting exposure to mosquitoes, ticks and other carriers of encephalitis.

About encephalitis

Encephalitis is a rare inflammation of the white and gray matter of the brain. Although it technically refers to any brain inflammation, the term encephalitis is most commonly used to describe inflammation caused by a viral infection.

Arthropod-borne viruses (arboviruses) play a significant role in the spread of encephalitis worldwide. Arthropods are insects and insect-like animals with a hard outer skeleton and jointed limbs, such as mosquitoes and ticks. Birds and mammals serve as hosts of the virus. A mosquito feeding on an infected animal becomes an encephalitis carrier for the remainder of its short life. The virus is then passed by the mosquito to other animals it feeds on, which, in turn, infects other mosquitoes feeding on that animal. Reptiles, amphibians and (in rare cases) humans also can serve as hosts of viruses that cause encephalitis. In most cases, the virus requires a vector and is not transmitted directly from one infected animal to another.

Viral infection can occur either directly in the brain and spinal cord (primary encephalitis) or spread to these areas from elsewhere in the body (secondary or postinfectious encephalitis). It is also possible, though uncommon, to contract encephalitis through other organisms, such as bacteria, fungi or parasites.

A swollen or irritated brain will not maintain normal blood flow, usually causing ailments such as fever, headache or confusion. Frequently, the root cause of encephalitis can also agitate or inflame frail tissue structures lining the brain and spinal cord (meninges). When the meninges become inflamed, this condition is known as meningitis. Encephalitis and meningitis often occur simultaneously, a condition called meningoencephalitis. In addition, encephalitis may be a complication of meningitis that is untreated, spreading infection from the meninges to brain.  When the spinal cord is also affected, the term encephalomyelitis may be used.

Most cases of encephalitis are mild and may not even produce noticeable symptoms. Encephalitis is most hazardous to infants, elderly people, individuals with weakened immune systems (e.g., cancer or HIV/AIDS patients) or people who live in areas with high mosquito populations. However, the disease can be potentially severe or even fatal to people of all ages.

Types and differences of encephalitis

Encephalitis can be classified several ways. The first involves its origin in the body:

  • Primary encephalitis. This type of encephalitis occurs when a virus invades the central nervous system (brain and spinal cord). It is the more serious although less common form of encephalitis.
  • Secondary (postinfectious) encephalitis. This form of encephalitis occurs when a virus first infects another part of the body and later enters the brain. It is more common than primary encephalitis although less serious. It may be mild enough to produce few symptoms and may not require medical care in some cases.

In addition, encephalitis may be classified according to its cause:

  • Viral encephalitis. The most common form, caused by infection from a virus. Herpes simplex virus (HSV) type 1 is the most common cause of encephalitis in the United States. Other viruses that cause encephalitis include arboviruses (transmitted through the bites of mosquitoes, ticks and sandflies), other herpes viruses (e.g., varicella-zoster virus, Epstein-Barr virus) and the rabies virus.
  • Parasitic or bacterial encephalitis. Rare forms of encephalitis caused by infection with roundworms (e.g., due to exposure to infected animal feces), other parasites (e.g., the parasites that cause toxoplasmosis) or bacteria (e.g., the bacteria that cause Lyme disease). The length of time required for incubation of these forms of encephalitis in humans varies, depending on the cause and severity. 

Encephalitis may be categorized by its method of transmission. This includes:

  • Arthropod–transmitted encephalitis. A type of viral encephalitis that occurs after being bitten by an arthropod (insects and insect-like animals with a hard outer skeleton and jointed limbs). Arthropods include mosquitoes, ticks, mites, spiders and crabs. These are further categorized according to the type of organism and/or the geographic location where the disease is most common.
  • Acute disseminated encephalomyelitis(ADEM).Typically a disease of prepubescent children, ADEM is rare in people over the age of 12. Signs and symptoms of ADEM are similar to those of multiple sclerosis. However, ADEM is usually associated with a preceding infectious disease or immunization.
  • Postvaccinal encephalitis. Occurs after a vaccination.

Encephalitis may also be categorized according to where it occurs in the body (e.g., cortical encephalitis affects only the brain’s cortex) or by accompanying conditions (e.g., purulent encephalitis is inflammation accompanied by brain abscesses). Other types of encephalitis include infantile encephalitis (caused by arboviruses or the herpes virus) and encephalitis periaxialis (inflammation of the white matter of the cerebrum), both of which usually affect infants and young children.

Arthropod-transmitted encephalitis

Arthropods are insects and insect-like animals with hard outer skeletons (exoskeletons) and jointed limbs. Arthropods include mosquitoes, ticks, mites, spiders and crabs. Viruses transmitted to humans by arthropods are called arboviruses. The arboviruses that cause encephalitis in humans are most often transmitted by mosquitoes.

A mosquito feeding on an infected animal becomes capable of transmitting the virus for the remainder of its brief lifespan. After exposure to the virus, it briefly exhibits very high levels of the virus until immunity develops. The mosquito then infects the next animal on which it feeds, thus passing the virus to more mosquitoes that feed on the same animal. Birds, horses, rabbits, chipmunks, bats, skunks, cats, squirrels and other mammals living in areas with high mosquito populations typically serve as hosts to viruses that can cause encephalitis.

This feeding cycle usually continues without considerable harm to either the carrier or host, and without reaching humans. Mosquitoes tend to bite birds and small mammals first, with humans being bitten as a second choice. However, certain unusual conditions, such as environmental disasters or inclement weather, can increase the risk of human infection by increasing mosquito populations in a given area.

Several different arboviruses, usually named for the geographic region in which they were discovered, can cause encephalitis in humans. Infected mosquitoes or ticks that serve as carriers or transmitters of these viruses are a growing health concern.

The most common arboviruses that can cause encephalitis include:

  • Japanese encephalitis (JE) virus. Although vaccines are available, the JE virus is the most lethal and common cause of arthropod-transmitted encephalitis worldwide. The U.S. Centers for Disease Control and Prevention (CDC) estimates that 30,000 to 50,000 cases of JE occur each year in Asia, with about 15,000 of those resulting in death. However, an average of only about one case per year of JE virus is reported in Americans who live or travel to Asia. Most people infected with the JE virus do not exhibit symptoms. However, of those who have symptomatic disease, about 30 percent experience some neurological impairment. The JE virus is prevalent in many tropical areas of Asia and the Indian subcontinent, with epidemics of JE occurring most frequently in the summer. Mosquitoes are the carriers and water birds tend to be the primary host of the JE virus. However, some agricultural animals (e.g., pigs) can also host the disease. JE is endemic in many areas of East Asia, although experts rarely recommend JE vaccination for Americans who are going to spend short periods of time there. Those who plan to spend longer periods of time may be urged to get vaccinated. To maintain long-term protection against JE, periodic booster vaccines are needed.
  • West Nile virus. A relative newcomer in the United States, the West Nile virus first appeared in North America in 1999. The virus is more commonly found in parts of Africa, Asia, Europe and the Middle East. As with most other forms of encephalitis, birds serve as the main animal hosts of the virus. In the United States, crows in particular were linked to West Nile virus. However, the disease can also be spread by humans during childbirth, breastfeeding, organ transplant and blood transfusions. Encephalitis caused by this arbovirus can be severe in older adults and/or those with compromised immune systems. In some cases, the virus may only cause fever and may not involve the nervous system (as meningitis and encephalitis do). In 2005, about 3,000 cases of infection by this virus were reported to the CDC, but fewer than 1,300 cases involved meningitis or encephalitis.
  • Venezuelan equine encephalitis (VEE) virus. This is a consistent health concern and a much more frequent cause of encephalitis in Central and South America than in the United States. However, presence of the VEE virus has been reported (primarily in horses) in the southwestern United States. Hosts of this virus tend to be forest rodents, with mosquitoes serving as carriers. Very few people infected with VEE virus actually develop encephalitis.
  • Tick–borne encephalitis (TBE) virus. The TBE virus is produced by three closely affiliated viruses: the western European subtype, the Siberian subtype and the far Eastern subtype. The TBE virus is present in a variety of host mammals and tick carriers throughout eastern Europe and Asia. Humans tend to be exposed to the TBE virus during the spring and summer in areas of the world with warm climates. Infection also occurs throughout the Mediterranean during the fall and winter. In rare cases, infection with the TBE virus can occur through the consumption of unpasteurized dairy products from sheep, goats or cows.
  • Colorado tick fever virus. Occasionally, people infected by this virus develop either encephalitis or meningitis. The virus is transmitted via the wood tick in parts of the western United States and Canada. Because of the mountainous geography of the region, wood ticks tend to live in elevations ranging from 4,000 to 10,000 feet (1,200 to 3,000 meters). The virus is usually transmitted between March and September, with peak periods of transmission occurring from April to June.
  • St. Louis encephalitis virus. This virus is transmitted to mosquitoes by infected birds. Encephalitis caused by this arthropod-transmitted virus tend to be mild and usually appear within five to 10 days after infection. About 130 cases of St. Louis encephalitis are reported each year in the United States, with annual fatality rates ranging from 3 to 30 percent, according to the CDC.
  • La Crosse encephalitis(LAC) virus. This virus was initially discovered in Wisconsin in 1963 and occurs in forested areas of the central United States. Unlike most cases of viral encephalitis in which birds are the primary host animal, the LAC virus is hosted mostly within chipmunks, squirrels and foxes before being transmitted to humans by mosquitoes. The CDC estimates about 70 cases are reported each year. Children are most susceptible, and this virus is the chief source of arbovirus infection in children in the United States.
  • Murray Valley encephalitis (MVE) virus. This virus is native to Australia, New Guinea and eastern Indonesia. Infection by the MVE virus in humans is extremely rare, although it can be fatal or cause severe neurological problems in some instances. Children and the elderly tend to be most at risk for contracting MVE.
  • Eastern equine encephalitis (EEE) virus. The EEE virus can cause some of the most severe manifestations of encephalitis. The virus is prevalent throughout North, Central and South America and the Caribbean. The EEE virus most commonly infects horses and very rarely humans. According to the CDC, four people on average are infected with EEE virus in the United States each year. Outbreaks of EEE in the United States occur most often along the Atlantic and Gulf coasts during August and September, although people living in the warmer Southern states are potentially susceptible to infection anytime during the calendar year.
  • Western equine encephalitis (WEE) virus. Like the EEE virus, the WEE virus infects mainly horses, not humans. The virus is found in the central and western plains areas of North America. Significant outbreaks of WEE among horses were common in this region during the 1950s and 1960s. However, a variety of factors have reduced outbreaks substantially since that time, including improved horse vaccination methods and declining horse populations. Very few humans infected with the WEE virus actually develop encephalitis. However, death or serious complications (e.g., brain damage) can occur in very rare cases, most notably among small children and infants.
  • Powassan virus. This virus causes encephalitis only extremely rarely in humans. It is native to portions of Canada and the Northeastern United States. According to the CDC, just over 30 cases of infection by this virus have been reported since its discovery in 1958. Transmitted by ticks, infections most commonly occur between June and September.
  • Chandipura virus. Very little is known about this virus. It is thought to be associated with bites from sandflies. Initial outbreaks of the disease occurred in India in 2004, when hundreds of children were stricken with fatal or otherwise severe encephalitis that was linked with infection by the Chandipura virus.
  • Lyme disease is an arthropod-transmitted disease that, in rare cases, may cause encephalitis. It is caused by bacteria (not viruses) that are transmitted to humans by ticks. The disease is common in rural and wooded areas of North America, Canada and Europe. It is named after the town of Lyme, Connecticut, where an outbreak of the disease was reported in the 1970s.

Risk factors and causes of encephalitis

While anyone can develop encephalitis, its occurrence is rare in the United States. Certain factors may increase the risk of encephalitis, including:

  • Age. Elderly people and very young children typically have weaker immune systems than individuals outside of these groups, and as a result tend to develop certain types of encephalitis more often.
  • Immune system problems. People with weakened immune systems are at greater risk of contracting encephalitis than otherwise healthy adults. These include people with HIV or AIDS, cancer and other conditions, as well as those taking medications that suppress the immune system (e.g., after an organ transplant).
  • Exposure to metals. Poisoning by exposure to or ingesting certain metals, such as lead, can cause encephalitis in some individuals.

In addition, a number of risk factors apply only to encephalitis transmitted by arthropods (insects and insect-like animals with a hard outer skeleton and jointed limbs), especially mosquitoes. Other arthropods include ticks, mites, spiders and crabs. Factors that increase the risk of arthropod-transmitted encephalitis include:

  • Season. Because mosquitoes tend to mate in the warmer summer months, this time of the year is also when most cases of encephalitis are reported.
  • Geography. Certain locations are more suitable for mosquitoes and ticks than others. Mosquitoes often lay their eggs in areas with standing water, whereas ticks usually live in areas with dense vegetation. Visiting or living in such areas increases one’s risk of contracting encephalitis.
  • Outdoor activity. Individuals who spend a proportionately high amount of work or leisure time outdoors are at greater risk for contracting arthropod–transmitted encephalitis, particularly during an outbreak.

Encephalitis is most often caused by a viral infection. It is less commonly caused by bacteria, fungi or parasites. Arthropods carrying arboviruses spread encephalitis when they bite humans. Cases of arthropod–transmitted encephalitis tend to occur in clusters within certain geographic regions or time periods. The germs that cause encephalitis may also be transmitted in other manners, including sexual activity and childbirth.

The viruses, bacteria, fungi and parasites that can cause encephalitis include:

  • Herpes simplex virus (HSV). Several types of herpes viruses can cause herpes simplex encephalitis (HSE). HSE is leading cause of fatal encephalitis cases in the United States. Several types of HSV infections can cause encephalitis:
    • HSV type 1 (HSV-1) is generally recognized as the virus that causes the common cold sores or fever blisters around the mouth area. While most cases of HSV-1 do not cause HSE, HSV-1 is responsible for nearly all cases of HSE in older children and adults. This occurs in about two out of every 1 million people each year. However, studies have shown that people with HSV-1 who have cold sores are no more likely to contract encephalitis than those with HSV-1 who do not have cold sores.
    • HSV type 2 (HSV-2) is more commonly known as the virus that causes genital herpes. Newborns can contract encephalitis at the time of a vaginal delivery if the mother has HSV-2.
  • Other herpes viruses. Similar herpes viruses may cause encephalitis, although much less often than HSV-1 and HSV-2. These include cytomegalovirus, Epstein-Barr virus and the varicella-zoster virus, which more commonly causes chickenpox and shingles.
  • HIV (human immunodeficiency virus). HIV, the virus that causes acquired immune deficiency syndrome (AIDS), can cause encephalitis in patients, most often in the early stages of illness.
  • Rabies and monkeypox.Incidences of rabies in humans are extremely rare. Raccoons are the most common carriers of the disease in the United States. Occasionally, rabies can cause encephalitis in humans. Monkeypox is a rare viral disease that occurs mostly in central and western Africa. Despite its name, it most often is transmitted by squirrels, rats, mice and rabbits. The monkeypox virus also can cause encephalitis.
  • Toxoplasmosis. Caused by the Toxoplasma gondii parasite. People can get toxoplasmosis through infected food or water or from coming into contact with infected cat feces. In rare cases, toxoplasmosis can cause encephalitis.
  • Childhood infections such as rubella (German measles), measles (rubeola) and mumps. In rare instances, children can develop encephalitis after recovering from these conditions. When encephalitis does occur, it is usually in reaction to antibodies that have been produced by the immune system. Symptoms of encephalitis in children under these circumstances tend to be moderate. Encephalitis caused by these conditions has become much more rare as childhood immunizations for them have become more widely used.

Signs and symptoms of encephalitis

Signs or symptoms of encephalitis can vary in scope, intensity and duration, depending on the nature and severity of infection. For example, cases of encephalitis associated with herpes simplex virus (HSV) may begin with behavioral changes or a loss of memory and occasional complaints of changes to the sense of smell and taste. Other forms of encephalitis may trigger symptoms similar to those of a mild case of the flu.

Symptoms of encephalitis can take anywhere from 1 to 30 days to appear, although most symptoms become apparent within 5 to 15 days after the initial infection. In most cases, symptoms tend not to be serious. However, encephalitis can be fatal in some instances.

Possible symptoms of mild cases may include:

  • Drowsiness
  • Headache (possibly severe)
  • Photophobia (aversion or sensitivity to light)
  • Stiffness in the neck or back
  • Fever
  • Convulsions or vomiting
  • Fatigue
  • Loss of balance

Severe encephalitis cases may include the above symptoms, as well as the following:

  • Bleeding within the brain (intercerebral hemorrhage)
  • Bulges in the soft areas (fontanels) of infant skulls
  • Confusion
  • Loss of consciousness
  • Loss of memory
  • Muscle weakness
  • Paralysis
  • Seizures
  • Sudden, severe dementia

Some of these symptoms are more likely to appear among certain age groups than among others. For example, infants are prone to symptoms of a stiff neck and bulges in the fontanels, while older children are more likely to experience severe headaches, lethargy, confusion and sensitivity to light. Meanwhile, adults are more likely to experience mental disturbances.

Left untreated, encephalitis can lead to coma and death. Children who are younger than a year are at higher risk of fatality or neurological damage than older children and adults. Immediate medical attention should be sought if encephalitis is suspected.    Encephalitis may occur along with inflammation of the membranes lining the brain (meningitis). When physicians are trying to diagnose meningitis, encephalitis or some combination of the two (meningoencephalitis), distinguishing symptoms may involve the patient’s brain function. Patients with meningitis may exhibit discomfort, lethargy or distraction by headache, but their cognitive function remains normal. Patients with encephalitis commonly exhibit aberrations in their brain function, such as speech or motion disorders, altered cerebral status or motor or sensory problems.

Diagnosis methods for encephalitis

Having a physician compile a patient’s medical history and perform a physical examination are the first steps toward diagnosing encephalitis. Secondary (postinfectious) encephalitis may be suspected if symptoms appear after contraction of another viral infection (e.g., after contracting a herpes infection).

Tests used to diagnose encephalitis may include:

  • Spinal tap (also known as a lumbar puncture). Involves inserting a needle directly into the lower spine area to extract fluid for laboratory testing. A spinal tap is the most common method used to diagnose encephalitis. Advances in the testing of DNA (the material that carries an organism’s genetic information) have made it possible to diagnose encephalitis through more detailed examination of spinal fluids. This may reveal the presence of the responsible organism or signs of general infection (e.g., a heightened white blood cell count that indicates the body is fighting infection).
  • Blood testing. Removal of a sample of blood (usually from a vein) for laboratory analysis. Certain causes of encephalitis, such as the West Nile virus, are detectable through blood testing. Analysis of blood may show a rise in antibodies to a particular virus or other indicators necessary to make a diagnosis. In some cases, other blood tests may be performed such as a polymerase chain reaction (PCR) to identify the virus’ DNA or by culturing a specific virus found in the blood.
  • Brain imaging. A CAT (computed axial tomography) scan or MRI (magnetic resonance imaging) that produces images of the brain may reveal swelling consistent with encephalitis. Pressure within the brain can often be observed through brain imaging, providing valuable insight about the likelihood of encephalitis infection prior to performing a spinal tap. Some imaging tests may be more appropriate than others. For example, MRI is typically preferred over CAT scans as a method of diagnosing herpes simplex virus type 1 (HSV-1) encephalitis. This is because CAT scans may appear normal during the initial days of illness, when the effectiveness of therapy is likely to be greatest.
  • Electroencephalography (EEG). A measure of the brain’s electrical activity. Electrodes that monitor electrical impulses of the brain are pasted or otherwise attached to the scalp. The electrodes send brain activity information to a special machine where it is recorded on paper. Abnormal readings may indicate the presence of encephalitis. However, normal results do not necessarily rule out the presence of encephalitis infection.
  • Brain biopsy. Removal of a sample of brain tissue for laboratory analysis. The patient is anesthetized and a small hole is drilled into the skull, followed by the insertion of a needle into the brain tissue. Computer–imaging techniques such as x-rays or MRI aid in this technique. A brain biopsy may be necessary in rare instances when diagnosis of encephalitis through other methods is not possible. This test has significant risks and is not commonly performed.

Treatment options for encephalitis

Treatment for a mild case of encephalitis consists primarily of supportive care, such as rest, maintaining a nutritious diet and drinking plenty of liquids. Over-the-counter pain relieving medications can reduce symptoms such as headaches and fever. The use of anti-inflammatory drugs may reduce puffiness or pressure in the head. Children and teens with encephalitis should not be given aspirin. Aspirin used after a viral infection can cause Reye syndrome, a rare but sometimes fatal condition.

More serious cases of encephalitis may require different types of treatment. Early therapy that is targeted at the specific nature of the illness can substantially reduce the likelihood of bodily damage and death. Delayed treatment is usually associated with a poorer prognosis. Patients with severe encephalitis may require hospitalization.

Treatment of serious cases of encephalitis may include:

  • Antibiotics are recommended. Although the infection may be viral, antibiotics can prevent an additional bacterial infection.
  • Antiviral therapy can be used for certain viruses (e.g., herpes simplex virus) susceptible to antiviral drugs. However, antiviral compounds have yet to be developed for all viruses (e.g., arboviruses).
  • Anticonvulsant medications can help with seizures.
  • Corticosteroids may be used to help reduce brain swelling and inflammation.
  • Nutritional supplements or feeding tubes may be needed.
  • Lights may be dimmed to help alleviate headaches, but not enough to create shadows, which may cause hallucinations.
  • Rehabilitative treatment (e.g., speech therapy, physical therapy, occupational therapy) can address lasting damage, such as behavioral changes or problems with physical mobility or function. Such treatment may be needed for some pediatric cases of encephalitis. Children under one year of age are more likely to experience neurological complications such as seizures, paralysis and developmental delays.

The prognosis for patients following treatment varies. Patients who experience mild cases of encephalitis typically experience an acute phase that lasts for up to two weeks before they slowly make a full recovery, without treatment. On the other hand, permanent impairment or death are sometimes associated with more severe cases.

Prevention methods for encephalitis

The most effective way to prevent encephalitis is to avoid the viruses or other microorganisms that may cause the condition. Vaccines are available for the arboviruses that cause Japanese encephalitisJapanese encephalitis and tick-

borne encephalitis. Taking appropriate action to guard against sexually transmitted diseases (e.g., genital herpes) is an important defense against encephalitis. It is equally important for children to be immunized against diseases such as chickenpox, measles (rubeola), mumps and rubella (German measles).

It is possible for anyone to contract arthropod-transmitted encephalitis. Accordingly, there are no fail–safe measures one can take to prevent exposure. However, there are certain strategies that will help reduce the likelihood of infection if an outbreak of the disease is apparent. These strategies include:

  • Wear protective clothing. Covering one’s arms and legs with long sleeves and pants between dusk and dawn can help prevent mosquito bites.
  • Use mosquito repellent with DEET. Mosquito repellent with a 10 to 30 percent concentration of DEET should be applied to skin and clothing in areas where mosquitoes are prevalent. As a general rule, a 10 percent concentration of DEET lasts about two hours, with higher concentrations lasting for longer lengths of time. Pregnant or breastfeeding women as well as children under 2 months of age should not use repellants with DEET. If ingested, DEET can cause birth defects in fetuses and death in small children.
  • Keep mosquitoes outside. Holes in screened doors and windows should be repaired in order to prevent easy access for mosquitoes to enter a home.
  • Avoid mosquito habitats. If possible, avoid activities in areas where mosquitoes are common.
  • Remove outside standing water sources. Mosquitoes lay eggs in standing water. Emptying common items such as birdbaths, drains, wheelbarrows and flowerpots will help reduce mosquito populations. Removing other objects where water can accumulate, such as old tires or containers, will also help. Municipalities also can help reduce mosquito breeding habitats by eliminating standing water in drainage ditches and collection tanks.
  • Check pets, such as dogs and cats, for ticks. Have your veterinatian prescribe tick repellant medication for these pets. Patients who live in areas with known tick populations should also check themselves and their children for ticks during tick season.
  • Pay attention to warning signs. Signs such as sick or dying birds and/or other animals dying from unknown causes may indicate an outbreak of encephalitis. If spotted, be sure to report such occurrences to the local health department.

Ongoing research regarding encephalitis

Recent research suggests that ACE inhibitors, a class of drugs used to treat high blood pressure and diabetic kidney disease, may treat encephalitis caused by the West Nile virus. Researchers are also investigating the effects of interferon therapy on patients with this type of encephalitis. Interferons are a group of proteins produced naturally in the body during viral infections. Its role is to help the immune system distinguish between infected and noninfected cells, targeting the infected ones for destruction. This therapy involves introducing encephalitis–immune cells to the body to lessen the effects of the West Nile virus. Although initial results have been promising, this treatment is still being researched and has yet to be approved for use.

Questions for your doctor about encephalitis

Preparing questions in advance can help patients have more meaningful discussions with healthcare professionals regarding their conditions. Patients may wish to ask their doctor the following questions related to encephalitis:

  1. What can I do to prevent exposure to encephalitis?
  2. How concerned should I be about encephalitis?
  3. What activities put me most at risk for exposure to encephalitis?
  4. How can I limit mosquito and tick populations around my house?
  5. What signs and symptoms may indicate I have encephalitis?
  6. What tests would you need to perform to diagnose encephalitis? What do they involve and how do I prepare for them?
  7. What type of encephalitis do I have? How did I get it?
  8. What are my treatment options, and which do you recommend?
  9. How serious is my condition?
  10. Am I likely to experience complications from encephalitis?
  11. Should my family and friends be tested for encephalitis?
Scroll to Top