Disease Description (Causes and Symptoms)
- Definition summary: Japanese encephalitis is an acute central nervous system infection (encephalitis) caused by infection with the Japanese encephalitis virus, transmitted by Japanese encephalitis vector mosquitoes (Culex species, commonly referred to as “small red house mosquitoes”). Mosquitoes acquire the virus from host animals such as cattle and pigs and transmit it by biting humans.
- Pathophysiology: After being bitten by an infected mosquito, the virus enters the bloodstream → in some cases, hematogenous spread occurs, followed by invasion of the central nervous system through cerebral blood vessels → encephalitis (inflammation of brain tissue) develops. Incubation period: 4–14 days.
- Main symptoms
- Most cases (approximately 95%): asymptomatic or mild fever
- When symptoms occur: high fever, headache, vomiting, abdominal pain, sensory abnormalities
- With progression: altered consciousness (coma), seizures, respiratory depression or respiratory paralysis, possible death
- Sequelae during recovery: cognitive impairment (intellectual disability), speech impairment, motor paralysis, etc. (sequelae occur in approximately 25% of cases)
- Occurrence characteristics: In temperate regions such as Korea, cases occur mainly from late July to late October, with a peak in early September.
Treatment Methods
- Principle: No specific antiviral treatment has currently been established as the standard, so symptomatic and supportive treatment is the mainstay.
- Acute-phase treatment (primarily in hospitals and intensive care units)
- Strict bed rest and intensive monitoring (neurological symptoms, respiration, hemodynamics)
- Airway management and respiratory support (mechanical ventilation if necessary)
- Fever management: antipyretics, cold compresses, etc.
- Seizure management: benzodiazepines initially, with anticonvulsants (e.g., phenytoin) if necessary
- Management of cerebral edema and increased intracranial pressure: fluid management, hyperosmolar therapy (mannitol, hypertonic solution), etc. (according to intensive care assessment)
- Appropriate antibiotics if a secondary bacterial infection (such as pneumonia or urinary tract infection) is suspected
- Nutritional, fluid, and electrolyte management and prevention of complications
- Outpatient and recovery-phase management
- Neurological rehabilitation (cognitive, motor, and speech therapy) and long-term follow-up
- Preventive treatment
- Vaccination: Vaccination during infancy is recommended (follow local public health guidelines)
- Precautions (points to note during treatment)
- As specific antiviral agents are not standard treatment, decisions should be made according to clinical research and expert guidance
- In cases of high fever, seizures, or decreased consciousness, immediate emergency department evaluation and hospitalization are necessary
- Symptoms may be more severe and the prognosis poorer in children and older adults, so early intensive treatment is important
Outpatient Visit Checklist (Including Preparation Items and Example Questions)
- Items to prepare (bring to the hospital)
- List of currently used medications (including prescription and nonprescription medicines and supplements)
- Medical history (especially neurological diseases, immunosuppression, and vaccination history)
- Recent onset date (including an estimate of when the mosquito bite occurred), and records of when symptoms began and how they progressed
- Copies of recent test results (blood tests, chest X-ray, etc.) or hospitalization records, if available
- Photos/videos of body temperature or seizure activity, if possible
- Allergy history (medication and vaccine allergies)
- Information useful to provide to the doctor during an outpatient visit
- Date fever began, date altered consciousness began, and characteristics of seizures (frequency and duration)
- Recent travel history (such as visits to rural areas or places near livestock barns), and information about seasonal exposure
- Symptom-checking checklist
- Presence and timing of fever/headache/vomiting/coma/seizures
- Whether there have been changes in movement, speech, or cognition
- In children: changes in feeding or activity level, decreased crying or responsiveness, etc.
Examples of General Questions to Ask the Doctor
- “What are the possible diagnoses for this condition, and how serious is the risk?”
- “What additional tests are needed (serum/cerebrospinal fluid tests, imaging, PCR, etc.)?”
- “What is the purpose of the treatment being given now, and what effects can be expected?”
- “How do you determine whether hospitalization or intensive care treatment is needed?”
- “What medication side effects or complications should I be especially careful about during treatment?”
- “How will rehabilitation or long-term follow-up be planned after recovery?”
Examples of Disease-Specific Questions
- “I (or my child) developed symptoms starting on (date) after being exposed to Japanese encephalitis. What tests should be performed immediately?”
- “I have not yet received the vaccination. Do I need to be vaccinated because of future travel or the area where I live? What are the timing and type of vaccination?”
(Reference diagnostic and epidemiological summary: incubation period 4–14 days, approximately 95% of infected people are asymptomatic, mortality is approximately 25% among symptomatic patients, and approximately 25% may develop neurological sequelae after recovery)