Summary about Disease
California encephalitis, also known as La Crosse encephalitis, is a viral disease transmitted to humans through the bite of infected mosquitoes. The La Crosse virus (LACV) is the primary cause, belonging to the California serogroup of viruses. It primarily affects children, causing inflammation of the brain (encephalitis). Most infections are mild, but severe cases can lead to long-term neurological problems or, rarely, death.
Symptoms
Symptoms typically appear 5-15 days after a mosquito bite. Mild symptoms may include:
Fever
Headache
Nausea
Vomiting
Fatigue
Lethargy More severe symptoms can include:
Seizures
Coma
Paralysis
Speech difficulties
Changes in mental status
Causes
California encephalitis is caused by the La Crosse virus (LACV), which is transmitted to humans primarily through the bite of infected Aedes triseriatus mosquitoes (the Eastern Treehole mosquito). These mosquitoes acquire the virus by feeding on infected small mammals, especially chipmunks and squirrels. The virus can also be passed from infected female mosquitoes to their eggs, allowing the virus to persist in mosquito populations from year to year.
Medicine Used
There is no specific antiviral treatment for California encephalitis. Treatment focuses on managing symptoms and providing supportive care. This may include:
Supportive care: Rest, fluids, and over-the-counter pain relievers (acetaminophen or ibuprofen) to manage fever and headache.
Hospitalization: Required for severe cases to monitor vital signs, manage seizures, and provide respiratory support if needed.
Anti-seizure medication: If seizures occur.
Is Communicable
California encephalitis is not directly communicable from person to person. It is only transmitted through the bite of an infected mosquito.
Precautions
Preventing mosquito bites is the best way to protect against California encephalitis. Precautions include:
Use insect repellent: Apply insect repellent containing DEET, picaridin, IR3535, oil of lemon eucalyptus (OLE), para-menthane-diol (PMD), or 2-undecanone according to the product label.
Wear protective clothing: Wear long-sleeved shirts, long pants, and socks when outdoors, especially during dawn and dusk when mosquitoes are most active.
Eliminate standing water: Remove standing water from around your home (e.g., in flower pots, tires, bird baths, gutters) to prevent mosquito breeding.
Use window and door screens: Make sure window and door screens are in good repair to keep mosquitoes out of your home.
Avoid mosquito-prone areas: If possible, avoid areas where mosquitoes are common, especially during peak mosquito activity times.
How long does an outbreak last?
Outbreaks of California encephalitis typically occur during the late spring, summer, and early fall months when mosquitoes are most active. The duration of an outbreak can vary depending on factors such as mosquito populations, environmental conditions, and the number of infected animals in the area. It typically lasts the duration of the mosquito season.
How is it diagnosed?
California encephalitis is diagnosed based on a combination of factors:
Clinical Symptoms: Symptoms consistent with encephalitis, particularly in children during mosquito season.
Travel History: Recent travel to or residence in areas where the virus is known to circulate.
Laboratory Testing:
Blood tests: To detect antibodies to the La Crosse virus (IgM and IgG).
Cerebrospinal fluid (CSF) analysis: Collected through a lumbar puncture (spinal tap) to detect the virus or antibodies in the fluid surrounding the brain and spinal cord.
PCR (polymerase chain reaction): Can detect the virus's genetic material in blood or CSF, especially early in the illness.
Timeline of Symptoms
Incubation Period: 5-15 days after the mosquito bite.
Initial Symptoms (1-3 days): Fever, headache, nausea, vomiting, fatigue.
Progression (variable): In some, symptoms resolve. In others, they worsen to include seizures, altered mental status, and neurological deficits. Severe symptoms typically develop within the first week of illness.
Recovery: Recovery time varies. Mild cases may resolve within a week or two. Severe cases can have long-term neurological sequelae, such as learning disabilities, paralysis, or seizures.
Important Considerations
California encephalitis is primarily a disease of children, particularly those under 16 years old.
While most cases are mild, severe cases can lead to long-term neurological problems.
There is no specific treatment for the virus itself, so management focuses on supportive care.
Prevention through mosquito bite prevention is crucial.
Public health surveillance and mosquito control efforts are important in managing the disease.
Consult a healthcare professional if you or your child develops symptoms of encephalitis, especially during mosquito season or after a mosquito bite.