A virus causes viral encephalitis, which is a brain inflammation. Permanent brain injury is the most significant possible risk. Children under the age of one year and people over the age of 55 are at a higher risk of developing life-threatening complications. Drugs to ease symptoms and, if necessary, antiviral medications are among the treatment choices.
A virus causes viral encephalitis, which is a brain inflammation. Some viral infections, such as measles and rubella, can proceed to include brain inflammation. Other microorganisms, such as bacteria, fungi, and parasites, can cause encephalitis, but viruses – namely the enteroviruses – are the most common cause.
Viruses that enter the bloodstream move to the brain, where they replicate. When the body detects an invasion, it activates its immune system. The brain swells as a result of this. The symptoms of viral encephalitis are caused by a combination of infection and immune response. Permanent brain damage is the most serious possible consequence of viral encephalitis. Life-threatening complications are more likely in children under the age of one year and people over the age of 55.
Symptoms
The following are some of the signs and symptoms of viral encephalitis:
- high temperature
- headache
- sensitivity to light (photophobia)
- general malaise
- stiff neck
- stiff back
- vomiting
- changes to personality
- confusion
- memory loss (amnesia)
- seizures
- paralysis
- coma.
Viruses that can cause encephalitis
Viruses capable of causing encephalitis include the following:
- enteroviruses – such as coxsackievirus, poliovirus and echovirus
- herpes simplex virus
- varicella zoster virus
- Epstein-Barr virus
- cytomegalovirus
- adenovirus
- rubella
- measles
- Murray Valley encephalitis (MVE) virus and Kunjin virus
- Japanese encephalitis virus.
Modes of transmission of viruses
Viruses propagate in many ways, with some being more contagious than others. The following are some examples of viral transmission modes:
- 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.
The immune system's reaction to infection
Viruses may grow and move to other regions of the body, including the spinal cord and brain, after they have obtained access to the circulation (the central nervous system). Blood or nerves provide access to the brain. The viruses enter brain cells after breaking the blood–brain barrier. The infected brain cells are disrupted, damaged, and eventually ruptured as a result of this.
Viruses have varied preferences for different parts of the brain. The herpes simplex virus, for example, prefers to infect the temporal lobes, which are positioned near each ear. The immune system's cells rush to the brain and begin battling the viruses. This results in the typical brain swelling (cerebral oedema). The symptoms of viral encephalitis are caused by both the illness and the body's attempts to combat the infection.
Complications
Babies, the elderly, and those with weakened immune systems are more susceptible to viral encephalitis consequences. The following are some of the complications:
- low blood pressure (hypotension)
- low oxygen levels in the blood (hypoxaemia)
- bleeding inside the brain (intracerebral haemorrhage)
- permanent brain damage
- death.
Diagnosis
A variety of tests are used to diagnose viral encephalitis, 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
- magnetic resonance imaging (MRI).
Treatments
Viruses, unlike bacteria, are difficult to cure. Antiviral drugs are only effective against a small number of viruses. The following treatments may be used to lessen the intensity of the symptoms:
- hospitalisation
- 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).
Prospects in the long run
The severity of viral encephalitis is determined by the infection and how promptly it was treated. The acute phase of the sickness usually lasts one or two weeks, and the symptoms may go away immediately or gradually fade away over time.
In many circumstances, the person recovers completely. In other circumstances, the individual may suffer from varied degrees of brain injury, necessitating long-term supporting care and counseling.