The recent West Nile virus outbreak is the largest ever in the United States, according to the Centers for Disease Control and Prevention, with the highest recorded number of cases through August since the disease was first detected in the United States in 1999. As of this earlier this week, 38 states had reported human infections, with a total of 1,118 cases, including 41 deaths.

Would you know if you had it? Symptoms for the mosquito-borne infection come in three categories of severity, from no symptoms at all to stupor and paralysis. And while milder forms of infection don't need medical attention, the more serious cases generally require hospitalization, so knowing the symptoms is important. Here is the rundown:

No symptoms
About 80 percent of people who are infected with the virus will not show any symptoms.

Mild symptoms: West Nile fever

Roughly 20 percent of people who become infected with West Nile Virus will develop West Nile fever. The following symptoms can last anywhere from a few days to several weeks:

  • Fever
  • Headache
  • Body aches
  • Nausea
  • Vomiting
  • Swollen lymph glands
  • Skin rash on the chest, stomach and back
Serious symptoms: West Nile encephalitis, West Nile meningitis, West Nile poliomyelitis

Things start to look more grim for the one in 150 people infected with West Nile virus who develop a severe illness. These symptoms can last for several weeks, and neurological effects may be enduring. Serious illness can happen to people of any age, although people older than 50 and those with compromised immune systems are at the highest risk for getting seriously ill. The severe symptoms can include:

  • High fever
  • Headache
  • Neck stiffness
  • Stupor
  • Disorientation
  • Coma
  • Tremors
  • Convulsions
  • Muscle weakness
  • Vision loss
  • Numbness
  • Paralysis
There is no cure of specific treatment for West Nile infection. People with milder West Nile fever recover on their own, though symptoms can be helped with various treatments (like medication for headache and body aches). If you develop symptoms of severe illness, seek medical attention immediately. 


The best way to avoid West Nile virus is to avoid mosquitos. Use repellants, wear long sleeves and pants — especially at dusk and dawn (or consider staying indoors during these hours). Make sure your screens are in good shape. Make sure you are not inadvertently creating mosquito farms with standing water. Empty water from flower pots, buckets, barrels and any other receptacles. Replace bird bath water weekly. Drill holes in tire swings and other containers so that water drains out. Keep vessels like children's wading pools empty and stored properly when they aren't being used.

More West Nile stories from MNN and partners:

West Nile virus: How to know if you're infected
The recent West Nile virus outbreak is the largest ever in the United States, according to the Centers for Disease Control and Prevention. Find out how to tell