Encephalitis California

a virus transmitted to humans via mosquito bite, causing St. Louis encephalitis. More and more cases are related to infection with HIV, the organism responsible for AIDS. Occasionally, encephalitis is a complication of other viral infections such as MEASLES or MUMPS.

Symptoms

Usually, symptoms begin with headache, fever, and prostration, leading to hallucinations, confusion, paralysis of one side of the body, and disturbed behavior, speech memory, and eye movement. There is a gradual loss of consciousness and sometimes a coma; epileptic seizures may develop. If the meninges are affected, the neck is usually stiff and the eyes are unusually sensitive to light.

Central nervous system symptoms include some (not all) of these:

• abnormal reflexes

• changes in consciousness

• disorientation

• inability to speak

• irritability

• listlessness

• odor hallucinations

• sleepiness

• spasticity

Diagnosis

Symptoms, signs, and the results of CT scans, EEG, and a spinal tap will help diagnose the disease.

Treatment

The antiviral drug acyclovir administered intravenously is an effective treatment for encephalitis caused by the herpes virus. If the disease is related to other viral infections, there is no known effective treatment. Depending on the virus causing the problem, some patients will die and some who recover will have brain damage, with mental impairment, behavioral disturbances, and epilepsy. Supportive care is the treatment of choice in these cases.

encephalitis, California The most common form of a group of viruses that cause encephalitis. First discovered in Central Valley, California, in 1943, this variety is the most common type of encephalitis and infects more boys than girls under age 15 in both rural and suburban areas. La Crosse encephalitis (a widespread encephalitis common in young children) belongs to this group.

The California virus belongs to a group of viruses called bunyavirus. It is a zoonosis (disease passed from animals to humans) and is carried by many different types of mosquitoes, which catch the virus from and give it to both squirrels and chipmunks in wooded areas. La Crosse encephalitis is carried by the Aedes triseriatus mosquito.

The infected mosquitoes remain infected for life; because the virus does not remain present in human blood, it is not possible to transmit the virus between humans.

Most adults who live in areas where the mosquitoes live are immune because they have antibodies produced when they were bitten as children. Elderly people may be susceptible, because the immunity appears to wear off with age.

Since the original virus was isolated, other viruses have been isolated that are closely related to California encephalitis. This group of related viruses is now classified as the California serogroup. Several other human pathogens (such as the La Crosse virus) also belong to the California serogroup. Although little human disease was associated with these viruses until 1960, now the California serogroup virus infections are the most commonly reported cause of mosquito-transmitted encephalitis in the United States. From 1996 to 1998 approximately three times as many reported human cases of mosquito-borne encephalitis were caused by the California serogroup viruses as were reported for western equine encephalomyelitis virus, St. Louis encephalitis, and eastern equine encephalitis viruses combined.

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