What is West Nile virus and can it cause meningitis?

WNV is a virus transmitted by mosquitoes. WNV can infect humans through the bite of a mosquito carrying the virus.

WNV can occur in some climates during mosquito season, such as late summer to early fall in temperate regions and year-round in southern regions.

WNV usually causes mild flu-like symptoms. In some cases, WNV can cause serious illnesses, such as meningitis.

A mosquito can become infected with WNV by feeding on infected birds. Mosquitoes can then transmit WNV if they bite humans or other mammals.

An infected mosquito bite is the The most common cause of WNV, but in rare cases it can also be transmitted by:

• exposure to WNV in the laboratory
• blood transfusion
• organ transplant
• a pregnant person to their baby, whether during pregnancy, childbirth or breastfeeding

WNV is not spread by any of the following:

• cough or sneeze
• human contact
• handling birds infected with WNV, dead or alive
• touch live animals
• eating an animal with WNV

In some cases, WNV can cause meningitis, which is inflammation of the lining of the brain and spinal cord.

WNV can also cause encephalitis, which is inflammation of the brain, or meningoencephalitis, which is inflammation of the brain and surrounding membranes.

If the virus crosses the blood-brain barrier, which helps protect the central nervous system, it can cause inflammation of the meninges, which are layers of membrane protecting the brain and spinal cord.

According to the Centers for Disease Control and Prevention (CDC), 8 out of 10 people infected with WNV will not show any symptoms of the virus.

The CDC states that 1 out of 5 people may develop symptoms, such as:

• fever
• headache
• aches
• articular pain
• vomiting
• diarrhea
• eruption
• fatigue
• weakness

In a few people, approximately 1 in 150WNV can cause encephalitis or meningitis, which can lead to the following symptoms:

• high fever
• headache
• neck stiffness
• stupor, which includes impaired consciousness, extreme lethargy, or decreased response to external stimuli
• disorientation
• coma
• tremors
• seizures
• muscular weakness
• vision loss
• numbness
• paralysis

A doctor may first take a medical history and assess symptoms.

To diagnose WNV, a doctor may perform a lumbar puncture. A doctor will insert a needle into the spinal canal to take a sample of cerebrospinal fluid. They may also do blood tests to check for the presence of WNV.

A doctor can then send the samples to a lab to check for the presence of WNV antibodies, which could indicate past or present infection. A lumbar puncture can also test for meningitis.

Viral culture tests can also help diagnose WNV from the fluid sample. Doctors may also perform reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry (IHC) tests to help with diagnosis.

WNV can cause serious illness in anyone, but people over 60 are at higher risk of serious illness from WNV infection.

People are also at higher risk of serious illness from WNV infection if they have certain medical conditions, including:

• cancer
• Diabetes
• high blood pressure
• kidney disease
• an organ transplant

There is currently no specific vaccine or medication to treat WNV. To treat mild symptoms, people can take over-the-counter pain relievers.

Some people who have a fever and other symptoms, such as headaches and body aches, make a full recovery, but may still feel tired or weak for weeks or months following infection.

To treat serious illness caused by WNV, such as meningitis, people may need treatment in hospital, which may include:

• intravenous fluids
• analgesic
• respiratory assistance if necessary
• prevention of secondary infections

Some people can recover from viral meningitis in 5 to 14 days without needing medical treatment.

Complications of WNV can include:

• encephalitis
• meningitis
• meningoencephalitis

Medical professionals may refer to them as West Nile neuroinvasive disease (WNVD).

People should seek immediate medical attention if they have the following symptoms:

• high fever
• headache
• neck stiffness
• stupor
• disorientation
• tremors
• seizures
• muscular weakness
• paralysis

People with WNVD may also suffer from a coma, which will require immediate emergency medical treatment.

According to CDC, the best way to protect yourself against WNV is to avoid mosquito bites. People can help protect themselves from mosquito bites by practicing the following:

• use an insect repellent, such as DEET or an Environmental Protection Agency-approved insect repellent
• spray repellent on any exposed skin but not on skin under clothing
• applying repellent after applying any other products, such as sunscreen
• wear long sleeves and pants
• treating clothing with an insecticide, such as permethrin 0.5%
• use screens on doors and windows
• if possible, use air conditioning
• using permethrin-treated mosquito nets above beds if needed
• empty standing water once a week

If people have mild symptoms of WNV, they may be able to treat the virus at home with rest and pain medication.

People should contact a doctor immediately if they have symptoms of serious illness from WNV:

• high fever
• headache
• neck stiffness
• disorientation
• stupor
• tremors
• seizures
• muscular weakness
• numbness
• vision loss
• paralysis
• coma

WNV is a virus transmitted by mosquitoes. Mosquitoes carrying the virus can transmit it to humans through a mosquito bite.

In most cases, people do not experience any symptoms of WNV. Some people may experience mild, flu-like symptoms, such as fever.

In severe cases, the virus can cross the blood-brain barrier and cause serious illness. WNV can cause meningitis, encephalitis or meningoencephalitis.

If people have severe symptoms, such as a stiff neck, muscle weakness, or high fever, they should seek medical attention immediately.