Viral Encephalitis – Basic microbiology, parasitology, and immunology; nature, reproduction, growth, and transmission of common microorganisms and parasites in Bangladesh; prevention including universal precaution and immunization, control, sterilization, and disinfection; and specimen collections and examination. Students will have an understanding of common organisms and parasites caused human diseases and acquire knowledge about the prevention and control of those organisms.
Neurotropic Viruses
- Poliovirus
- Rabies virus
- Herpes simplex virus.
- Mumps
- Measles
- Coxsackie virus
- Echo virus
Viral Encephalitis
Viral encephalitis is typically caused by a viral infection. The most common causes of viral encephalitis are herpes simplex virus types 1 and 2, varicella zoster virus and enteroviruses, which cause gastrointestinal illness.
Signs and Symptoms
Most people with viral encephalitis have mild flu-like symptoms, such as
- Headache
- Fever
- Aches in muscles or joints
- Fatigue or weakness
Sometimes the signs and symptoms are more severe, and might include:
- Confusion, agitation or hallucinations
- Seizures
- Loss of sensation or paralysis in certain areas of the face or body
- Muscle weakness
- Problems with speech or hearing
- Loss of consciousness (including coma)
In infants and young children, signs and symptoms might also include:
- Bulging in the soft spots (fontanels) of an infant’s skull
- Nausea and vomiting
- Body stiffness
- Poor feeding or not waking for a feeding
- Irritability
Causes of Viral Encephalitis:
The viruses that can cause encephalitis include:
➤ Herpes simplex virus (HSV).
➤ Other herpes viruses.
➤ Enteroviruses
➤ Mosquito-borne viruses. These viruses can cause infections such as West Nile, La Crosse, St. Louis, western equine and eastern equine encephalitis.
➤ Tick-borne viruses.
➤ Rabies virus
➤ Childhood infections. Common childhood, infections – such as measles (rubeola), mumps and German measles (rubella) used to be fairly common causes of secondary encephalitis. These causes are now rare in the United States due to the availability of vaccinations for these diseases.
Complications:
Inflammation can injure the brain, possibly resulting in a coma or death. Other complications varying greatly in severity may persist for months or be permanent. These complications can include
➤ Persistent fatigue
➤ Weakness or lack of muscle coordination
➤ Personality changes
➤ Memory problems
➤ Paralysis
➤ Hearing or vision defects
➤ Speech impairments
Prevention
The best way to prevent viral encephalitis is to take precautions to avoid exposure to viruses that can cause the disease. Try to:
- Practice good hygiene: Wash hands frequently and thoroughly with soap and water, particularly after using the toilet and before and after meals.
- Don’t share utensils: Don’t share tableware and beverages.
- Teach children good habits: Make sure they practice good hygiene and avoid sharing utensils at home and school.
Modes of Transmission
Viruses spread by different means, and some are more infectious than others. Some of the modes of viral transmission include:
➤ Coughs or sneezes from an infected person that release airborne viruses, which are then inhaled by others
➤ Infected insects (such as mosquitoes or ticks) and animals, which can transfer some viruses directly into the bloodstream via their bite
➤ Eating contaminated food or drink
➤ The transfer of some viruses can occur through touching an infected person
➤ There is evidence to suggest that some cases of viral encephalitis are caused by a dormant viral infection (such as herpes simplex virus) becoming active again.
Diagnosis
Viral encephalitis is diagnosed using a number of tests including:
➤ Physical examination
➤ Blood tests
➤ Laboratory examination of cerebrospinal fluid (clear liquid that bathes the brain and spinal cord) removed via a lumbar puncture (a procedure in which a small needle is inserted into the lower part of the spine)
➤ Computed tomography (CT) scan
➤ Electroencephalography (EEG) to measure brain waves
➤ Computed tomography (CT) scan
➤ Electroencephalography (EEG) to measure brain waves
Treatment of viral encephalitis
➤ Hospitalization
➤ Antiviral medication, given intravenously, if the virus is known to be susceptible to treatment with antiviral medication (such as the herpes simplex virus)
➤ Intravenous administration of medications to help reduce brain swelling
➤ Pain-relieving medication
➤ Medication to prevent vomiting
➤ Medication to prevent seizures (anticonvulsant)
➤ Medication to reduce fever, such as paracetamol
➤ Fluids to prevent dehydration, but not too much as this can worsen cerebral oedema (swelling of the brain).
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