Table of ContentsView AllTable of ContentsFrequent SymptomsComplicationsWhen to See a DoctorFrequently Asked Questions
Table of ContentsView All
View All
Table of Contents
Frequent Symptoms
Complications
When to See a Doctor
Frequently Asked Questions
West Nile fever is a mosquito-borne viral infection of which 75 percent of cases will have little to no recognizable symptoms. The remaining 25 percent may develop a fever, headache, vomiting, or rash. While the West Nile virus rarely causes major illness in healthy adults or children, those with compromised immune systems (such as the elderly and people living with HIV) are at an increased risk of severe complications, including meningitis and encephalitis.
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People infected with theWest Nile viruswill typically develop symptoms within two to 14 days of exposure.The most common symptoms include:
The symptoms tend to be mild and may last for a few days or weeks. In absence of a rash, people will often describe the infection as being similar to a mild flu or a bad summer cold. More often than not, the symptoms will resolve on their own without treatment.
The West Nile virus is a neurotropic virus, meaning that it preferentially attacks the nervous system. In the vast majority of cases, the body’simmune defensescan control and eventually neutralize the virus on their own.
However, the same may not hold true for people whoseimmune systems are compromised. This places certain groups—such as the elderly, organ transplant recipients, people withadvanced HIV, and those undergoing cancer chemotherapy—at an increased risk of severe and potentially life-threatening complications.
The types and severity of symptoms are largely dependent on the parts of the nervous system affected. Collectively, the complications are referred to as West Nile neuroinvasive disease (WNND) and include encephalitis, meningitis,meningoencephalitis, and poliomyelitis. Overall, WNND is associated with a 9 percent risk of death.The rate is believed to be higher in the elderly.
West Nile Encephalitis
West Nile encephalitis is the most common manifestation of WNND.It typically causes fever, headaches, confusion, forgetfulness, extreme lethargy, and changes in personality or behavior.
Between 30 percent and 50 percent of people with West Nile encephalitis will experience unilateral muscle weakness (meaning on one side of the body). Of these, some may progress to flaccid paralysis,a type of paralysis in which muscles are unable to contract.
West Nile Meningitis
West Nilemeningitisis a condition in which the virus causes the inflammation of the meninges, the three membranes that surround and encase the brain and spinal cord. While meningitis can cause many of the same physical symptoms of West Nile encephalitis, it doesn’t typically alter a person’s behavior or personality, or cause confusion. Nausea, vomiting, neck pain or stiffness, light sensitivity (photophobia), and the fear of loud sounds (phonophobia) are also common.
West Nile Meningoencephalitis
West Nile meningoencephalitis is a complication affecting both the brain and meninges. Men between ages 60 and 89 are 20 times more likely to develop West Nile meningoencephalitis than the general population, while people with compromised immune systems are at a 40-fold increased risk.
While meningoencephalitis shares many of the same neurologic symptoms of meningitis and encephalitis, they tend to be more severe and longer lasting (and may, in some cases, become permanent) with this particular complication. The risk of death is also higher, hovering between 12 percent and 15 percent. The mortality risk among the elderly may be as high as 35 percent.
West Nile Poliomyelitis
Less commonly, West Nile poliomyelitis can affect the respiratory systemand require mechanical ventilation to help the person breath. It can also cause the loss ofsphinctercontrol, resulting inurinaryorfecal incontinence.
While the paralysis may lead to permanent impairment, milder cases can often improve significantly as the affected nerve cells gradually recover and reestablish connections. People with fewer affected limbs tend to show better improvement overall. With that being said, most of the strength recovery will occur during the first six to eight months following the onset of symptoms, eventually plateauing with less noticeable improvement.
West Nile Reversible Paralysis
What differentiates West Nile reversible paralysis from West Nile poliomyelitis is that the reflex responses remain intact even when muscle weakness occurs. While the initial paralysis can be profound, it will eventually reverse with little visible impairment of motor function.
Getting a mosquito bite does not mean you will get West Nile fever. Most people infected with the West Nile virus will either never even know it or simply mistake it for a mild flu. Even if you discover you’ve been infected, the chances are good that you will get better without any problems or treatment.
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With that being said, if you are elderly or immune-compromised, you need to seek immediate care if you experience a severe headache, high fever, neck stiffness, confusion, light sensitivity, or sudden muscle weakness. These may be signs encephalitis or meningitis, both of which require emergency treatment.
The West Nile virus is no longer a disease associated with foreign travel. You can get it in the United States as readily as Africa and the Middle East. Fatalities, which have mainly occurred among the elderly, have generally been low, the annual rate ranging from as few as 2 to as many as 286 in the United States.
Around 80% of people infected with the West Nile virus will experience no symptoms. Of those that do, one in five will develop fever, fatigue, rash, muscle aches, joint pain, diarrhea, and/or vomiting.
With mild infections, the febrile (fever-related) symptoms may resolve within days, but the fatigue and weakness can persist for weeks and even months in some people.
One in 150 infections will result in West Nile neuroinvasive disease (WNND), in which the virus invades the central nervous system. Symptoms may include severe headache, neck stiffness, muscle weakness, tremors, disorientation, convulsions, paralysis (typically reversible), and coma.
There is no specific treatment for West Nile fever. Even so, the vast majority of people will recover without treatment or long-term consequences. Severe cases may require hospitalization to treat complications of the disease and preventsecondary infections.
Symptoms of West Nile Virus
12 Sources
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