Mosquitoes can transmit the viruses for several types of encephalitis, including West Nile encephalitis, St. Louis encephalitis, and Western Equine encephalitis.
One of the most dangerous and most common causes of encephalitis is the herpes simplex virus (HSV). HSV is the same virus that causes cold sores around the mouth, but when it attacks the brain it may occasionally be fatal. Herpes simplex encephalitis is caused by the herpes simplex virus that manifests in oral cold sores or genital sores.
When this triggers brain inflammation, which occurs in 10% of cases of encephalitis (2 cases per million people), half of all untreated patients die (1 case per million people). Brain damage, partial paralysis, seizures, hallucinations and an altered state of consciousness are all common symptoms. HSE can be passed from mother to child during birth in rare cases, where symptoms include lethargy, tremors, irritability, seizures and poor feeding in the first two weeks after birth.
Patients with encephalitis suffer from fever, headache and photophobia with weakness and seizures also common. Less commonly, stiffness of the neck can occur with rare cases of patients also suffering from stiffness of the limbs, slowness in movement and clumsiness depending on which specific part of the brain is involved. The symptoms of encephalitis are caused by the brain's defense mechanisms activating to get rid of the infection.
Encephalitis takes two forms, categorized by the two ways that viruses can infect your brain:
This occurs when a virus directly invades your brain and spinal cord. It can happen to people at any time of the year (sporadic encephalitis), or it can be part of an outbreak (epidemic encephalitis).
Secondary (post-infectious) encephalitis.
This form occurs when a virus first infects another part of your body and secondarily enters your brain.
The primary form of the disease is more serious, while the secondary form is more common. But because of the milder nature of secondary encephalitis, doctors actually see more cases of primary encephalitis.
Signs and Symptoms
Milder forms of encephalitis can follow or accompany common childhood illnesses, including measles, mumps, chickenpox, rubella (German measles), and mononucleosis.
Symptoms in milder cases of encephalitis usually include:
loss of energy
a general sick feeling
In more severe cases of encephalitis, a person is more likely to experience high fever and any of a number of symptoms that relate to the central nervous system, including:
nausea and vomiting
problems with speech or hearing
It's harder to detect some of these symptoms in infants, but important signs to look for include:
a full or bulging soft spot (fontanel)
crying that doesn't stop or that seems worse when an infant is picked up or handled in some way
For most forms of encephalitis, the acute phase of the illness (when symptoms are the most severe) usually lasts up to a week. Full recovery can take much longer, often several weeks or months.
See your doctor if you experience signs and symptoms of primary or secondary encephalitis because the course of the disease is unpredictable.
Seek immediate medical attention if your child has any of the following symptoms:
inability to look at bright lights
problems with speech
sudden personality changes
problems with memory
extreme drowsiness or lethargy
loss of consciousnes or hearing
difficulty moving an arm or leg
loss of sensation anywhere in the body
If your infant has any of the following symptoms, seek immediate medical care:
high fever or any fever higher than 100.4 Deg Fahrenheit (38 Deg Celsius) in infants younger than 3 months of age.
fullness or bulging in the soft spot
poor appetite or reduced feeding
crying that won't stop
floppiness or decreased tone
Treatment is usually symptomatic.
Reliably tested specific antiviral agents are available only for a few viral agents (e.g. acyclovir for herpes simplex virus) and are used with limited success for most infection except herpes simplex encephalitis.
In patients who are very sick, supportive treatment, such as mechanical ventilation, is equally important.
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