Disease Description (Causes and Symptoms)
- Causes and pathophysiology
- West Nile fever is a type of arboviral infection caused by West Nile virus (WNV). It is primarily transmitted when an infected mosquito bites a person. In nature, birds are the main hosts and mosquitoes serve as vectors. In rare cases, it may be transmitted through blood transfusion, organ transplantation, vertical transmission, or laboratory exposure.
- The risk of neurological involvement (encephalitis, meningoencephalitis, myelitis, etc.) is increased in older adults and immunocompromised people.
- Main symptoms
- Usually asymptomatic or mild: fever, headache, myalgia, malaise, nausea and vomiting, decreased appetite, lymphadenopathy, eye pain, etc.
- Skin rash: Approximately half of patients with mild disease may develop a transient rash on the back, chest, and upper limbs (improving within about one week).
- Neurological involvement (rare but severe): altered mental status, severe muscle weakness, flaccid paralysis, seizures, cranial nerve abnormalities, optic neuritis, etc.
- Diagnostic summary
- Diagnosis is based on detection of WNV-specific IgM in serum or cerebrospinal fluid (or a fourfold increase in serum antibody titer), detection of viral genetic material (PCR) or antigen, or virus isolation.
Treatment Methods
- Standard treatment
- There is currently no established antiviral medication or human vaccine. Treatment is primarily symptomatic and supportive.
- Mild cases: hydration, antipyretic and analgesic treatment, and rest.
- In cases of neurological involvement: hospitalization and intensive care at the level of an intensive care unit may be required (including respiratory support, seizure treatment, and intracranial pressure management).
- Specific management: anticonvulsants for seizures; physical therapy and rehabilitation for muscle weakness and paralysis; prevention and treatment of secondary bacterial infections.
- Precautions/self-care
- Be attentive to fever and dehydration. If symptoms worsen (decreased consciousness, difficulty breathing, progressive motor weakness, etc.), immediately visit an emergency medical facility.
- During the acute phase, do not donate blood or organs (follow the guidelines of the relevant institution).
- Complications
- Rare but serious complications may occur, including neurological sequelae (persistent muscle weakness and neurological deficits), myocarditis, pancreatitis, and hepatitis. The mortality rate increases with neurological involvement (from a few percent to the range of 10% depending on the report).
Checklist Before an Outpatient Visit (Including Items to Prepare/Confirm and Example Questions)
- Items to bring/prepare
- A list of all medications currently being taken (including prescription drugs, over-the-counter drugs, and supplements)
- Past medical history (including immunosuppression and any recent blood transfusion or organ transplantation)
- A record of when symptoms began and how they have progressed (such as the date fever began and the dates of rash or neurological symptoms)
- Recent overseas travel history (endemic areas), outdoor activities, and possible mosquito exposure
- Any existing test results (blood tests, imaging, previous antibody tests, etc.)
- Key information to tell the doctor during the outpatient visit
- Whether neurological symptoms such as fever, headache, muscle weakness, or altered consciousness are present, and how quickly they are progressing
- Whether there has been a recent blood transfusion, organ transplantation, pregnancy, or immunosuppressed state
- Representative example questions (sentences patients can use themselves)
- "When did the symptoms begin?"
- "Have you recently received a blood transfusion or organ transplant?"
- "Have you traveled overseas recently or been bitten by many mosquitoes?"
General Example Questions to Ask the Doctor
- What are the side effects of this medication? (Regarding currently prescribed antipyretic and symptomatic-treatment medications)
- If my symptoms worsen, under what circumstances should I go to the emergency room?
- How likely is it that I will need hospitalization or intensive care treatment?
- How likely is it that I will develop sequelae (muscle weakness or neurological symptoms) after recovery?
- When can I donate blood or organs after the infection?
Disease-Specific Example Questions
- I have recently developed severe muscle weakness (especially flaccid paralysis of the limbs). Should neurological involvement be suspected? What tests should be performed first?
- I have a fever after recently receiving a blood transfusion (or organ transplant). Do I need to be tested for West Nile virus infection? Where can I get tested?
(Note: Diagnosis is made through WNV IgM/IgG testing of serum and cerebrospinal fluid, PCR, and, if necessary, referral to public health authorities or specialized institutions. Follow local public health guidelines and the hospital's infection-control guidelines.)