West Nile Virus
Also known as WNV infection
This article is general health information for the selected condition. It is not a diagnosis and does not replace clinical judgement. If you have questions or need treatment advice, please consult a qualified healthcare professional.
What is west nile virus?
West Nile virus is spread to people by the bite of infected mosquitoes. Around 80 percent of infected people have no symptoms at all, and most others have a mild flu like illness. Fewer than one percent develop neuroinvasive disease affecting the brain or spinal cord, which can be severe and leave lasting deficits.
Causes
- West Nile virus, a flavivirus
- Bite of an infected Culex mosquito
- Birds acting as the main reservoir
- Rarely blood transfusion, transplant or transmission in pregnancy
Symptoms
- No symptoms in the majority of infections
- Fever, headache and body aches
- Fatigue that can persist for weeks
- Rash on the trunk
- Swollen lymph nodes
- Neck stiffness, confusion or seizures in neuroinvasive disease
- Muscle weakness or paralysis in rare cases
Risk factors
- Age over 60 for severe disease
- Outdoor activity in summer and early autumn
- Living in areas with active transmission
- Immunosuppression
- Diabetes, hypertension and kidney disease
Diagnosis
- Serology for West Nile specific IgM antibodies
- Cerebrospinal fluid testing in suspected neuroinvasive disease
- PCR testing, most useful in immunocompromised patients
- MRI brain where encephalitis is suspected
- Public health notification
Treatment
- No specific antiviral treatment available
- Supportive care with fluids and analgesia
- Hospital care for neuroinvasive disease
- Respiratory support in severe cases
- Rehabilitation for persisting weakness
- Mosquito bite prevention as the main protection
Self care
- Rest and maintain fluid intake
- Use paracetamol for fever and aches
- Expect fatigue to persist for weeks
- Protect others by preventing mosquito bites at home
- Gradually resume activity rather than pushing through fatigue
When to see a doctor
Book an appointment if:
- Fever after mosquito exposure in an affected area
- Persistent severe headache
- Fatigue lasting beyond a few weeks
- Muscle weakness after a febrile illness
- Being over 60 or immunosuppressed with symptoms
- Symptoms recurring after apparent recovery
Some symptoms need emergency care rather than an appointment. See the warning signs listed above.
Prevention
- Use insect repellent containing DEET
- Wear long sleeves and trousers at dawn and dusk
- Fit and repair window and door screens
- Remove standing water around the home
- Avoid outdoor activity at peak mosquito times
- There is no human vaccine currently
Outlook
Around 80 percent of infections cause no symptoms and most others produce a mild illness that resolves within a week or two, though fatigue can persist for months. Fewer than one percent develop neuroinvasive disease, which carries significant mortality in older adults and can leave lasting weakness or cognitive difficulty.
Common questions
How can infection be prevented?
There is no human vaccine, so prevention relies on avoiding mosquito bites. Use repellent containing DEET, wear long sleeves at dawn and dusk, use screens, and remove standing water around the home.
Is it spread between people?
Not through ordinary contact. Rare transmission has occurred through blood transfusion, organ transplantation, pregnancy and breastfeeding, which is why blood supplies are screened in affected regions.
How long does recovery take?
Mild illness usually resolves within a week or two, though fatigue can linger for months. Neuroinvasive disease may leave lasting weakness or cognitive problems and often requires prolonged rehabilitation.
References
Important: Dard AI is not a medical device and does not diagnose, treat, or replace clinician judgement. This article is general information only. Always consult a qualified healthcare professional about diagnosis and treatment, and seek emergency care for severe or rapidly worsening symptoms.