Zika virus infection

Disease Description (Causes and Symptoms)

• Cause: Infection caused by Zika virus (a virus in the Flavivirus family). The main vectors are mosquitoes of the genus Aedes (e.g., Aedes aegypti, Aedes albopictus). Transmission through blood transfusion, sexual contact, and vertical transmission from mother to fetus has also been reported.
• Pathophysiology: The virus multiplies in the skin and then spreads through the bloodstream. In some cases, it may affect the nervous system (the peripheral nervous system in adults and the central nervous system in newborns and fetuses) (Guillain–Barré syndrome, congenital Zika syndrome).
• Main symptoms: The incubation period is 2–14 days. Most cases are asymptomatic (approximately 75–80%). When symptoms occur, mild fever, a generalized rash, joint pain (especially in the hands and feet), conjunctivitis (red eyes), muscle pain, and headache usually persist for 2–7 days. Infection during pregnancy may be associated with fetal microcephaly and neurodevelopmental abnormalities (the association is under investigation, and evidence continues to accumulate).

Treatment

• Basic principles: There is no specific antiviral medication. Symptom relief and supportive care are standard.
  • Rest and adequate fluid intake.
  • Fever and pain relief: Acetaminophen is recommended. Avoid aspirin and NSAIDs (e.g., ibuprofen) until dengue fever has been ruled out (because of the risk of bleeding).
  • If severe complications occur (e.g., neurological symptoms or progressive respiratory muscle paralysis), hospitalization, neurological and intensive care evaluation, and intensive treatment are required.
• Care during pregnancy:
  • If exposure or infection is suspected, immediate consultation with an obstetrician and gynecologist, blood and urine testing, and fetal follow-up (ultrasound) are recommended.
  • Fetal monitoring: When infection is confirmed or suspected, regularly monitor skull and brain development with ultrasound (e.g., at 3–4-week intervals). Additional diagnostic tests (e.g., amniocentesis) should be decided after consultation based on the individual situation.
• Public health and preventive measures:
  • Mosquito control and personal protection (repellent, long clothing, mosquito nets), as well as isolation of infected individuals (preventing mosquito exposure), etc.
  • To prevent sexual transmission, condom use or abstinence for a certain period is recommended when having sexual intercourse with a person with confirmed infection or a person who has been exposed (men: at least 3 months after exposure or symptoms is recommended; women: at least 2 months after exposure is recommended—confirm the recommendations of the relevant public health authorities according to the circumstances).

Checklist Before an Outpatient Visit (Including Example Questions)

• Items and information to prepare:
  • Recent travel history (countries visited abroad, length of stay, and date of return) and history of mosquito exposure
  • Whether pregnant (for women) and gestational age (if applicable)
  • Travel history and symptoms of sexual partners (possibility of sexual transmission)
  • Date symptoms began (fever, rash, etc.) and records of their progression (photos are acceptable)
  • Medications currently being taken (especially anticoagulants and anti-inflammatory drugs)
  • Copies of previous blood test and ultrasound results (if pregnant)
• Items to tell the healthcare provider in advance during the outpatient visit:
  • History of staying abroad and mosquito bites within the past 2 weeks
  • Recent history of blood transfusion
  • Neurological symptoms (numbness or weakness in the limbs, difficulty breathing, etc.)
• Example questions (questions the patient can write down in advance):
  • When did the symptoms begin?
  • Please take photos of the rash and conjunctivitis and bring them.

Examples of General Questions to Ask the Doctor

• "What do the test findings (genetic detection/IgM) mean? Are additional tests needed?"
• "What treatment do you recommend for my current symptoms? What are the side effects of this medication?"
• "If I am pregnant, how will fetal follow-up testing be carried out? What will be the frequency and possible types of tests?"
• "What preventive measures should I take regarding future travel, sexual activity, blood donation, and other activities?"

Examples of Disease-Specific Questions

• "If I am exposed to Zika virus during pregnancy (or have a positive test), what tests should be performed for the fetus, when should they start, and how often should they be performed?"
• "My IgM test is positive, but I have a history of previous dengue or yellow fever vaccination. Considering the possibility of cross-reactivity, should an additional confirmatory test (e.g., PRNT) be performed?"

(References and Additional Information)

• Diagnosis: Blood or urine RT-PCR (sensitive early in infection), IgM antibody testing (at a later time after exposure), and PRNT as an aid to confirmation. Test sensitivity and specificity vary depending on the timing and pre-existing flavivirus immunity.
• Reporting and public health: In some countries (e.g., South Korea), there is a legal obligation to report cases to public health authorities as a notifiable infectious disease.
• Prognosis: Most cases are mild and resolve, but long-term complications may occur in pregnant women and newborns (congenital Zika syndrome). Guillain–Barré syndrome is rare but may be serious.