West Nile fever

West Nile fever is an infectious disease caused by the West Nile virus (WNV). It is a member of the Flavivirus genus, which also includes other viruses such as dengue virus, yellow fever virus, and Zika virus. The disease is primarily transmitted to humans through the bite of an infected mosquito, particularly species of the Culex genus.

Transmission

West Nile virus is maintained in nature through a cycle involving transmission between birds and mosquitoes. Birds are the primary hosts of the virus, and mosquitoes become infected when they feed on infected birds. Infected mosquitoes can then transmit the virus to humans and other animals through their bites. Human-to-human transmission is rare but can occur through blood transfusion, organ transplantation, and from mother to baby during pregnancy, delivery, or breastfeeding.

Symptoms

Most people (approximately 80%) infected with West Nile virus do not develop any symptoms. About 20% of infected individuals develop a mild illness known as West Nile fever. Symptoms of West Nile fever can include:

• Fever
• Headache
• Body aches
• Joint pains
• Vomiting
• Diarrhea
• Rash

A small percentage of infected individuals (less than 1%) develop severe neurological illness, such as encephalitis or meningitis. Symptoms of severe disease can include:

• High fever
• Severe headache
• Stiff neck
• Disorientation or confusion
• Coma
• Tremors or muscle jerking
• Seizures
• Partial paralysis or muscle weakness

Diagnosis

Diagnosis of West Nile fever is typically based on a combination of clinical symptoms and laboratory tests. Serology tests, such as the detection of IgM antibodies in blood or cerebrospinal fluid, are commonly used to confirm infection. Polymerase chain reaction (PCR) tests can also detect viral RNA in blood or other tissues.

Treatment

There is no specific antiviral treatment for West Nile fever. Management of the disease is primarily supportive and may include:

• Pain relievers to reduce fever and relieve symptoms
• Intravenous fluids for hydration
• Hospitalization for severe cases, particularly those with neurological involvement

Prevention

Preventive measures focus on reducing exposure to mosquito bites. These measures include:

• Using insect repellent containing DEET, picaridin, or other EPA-registered ingredients
• Wearing long-sleeved shirts and long pants
• Installing or repairing window and door screens to keep mosquitoes out
• Eliminating standing water around homes to reduce mosquito breeding sites

Epidemiology

West Nile virus is found in many parts of the world, including Africa, Europe, the Middle East, North America, and West Asia. The virus was first identified in the West Nile district of Uganda in 1937. Since then, it has spread to various regions, causing outbreaks of West Nile fever and severe neurological disease.

See also

• Flavivirus
• Mosquito-borne diseases
• Encephalitis
• Meningitis