|
|
West Nile Virus
DefinitionWest Nile virus is transmitted by mosquitos and causes an illness that ranges from mild to severe. Mild, flu-like illness is often called West Nile fever. More severe forms of disease, which can be life-threatening, may be called West Nile encephalitis or West Nile meningitis, depending on where it spreads.
Pictures & Images
 See all Pictures & Images
Overview, Causes, & Risk Factors
West Nile virus is a type of organism called a flavivirus and is similar to many other mosquito-borne viruses, including Japanese encephalitis (which is found in Asia). Researchers believe the virus is spread when a mosquito bites an infected bird and then bites a person.
West Nile virus was first identified in 1937 in the West Nile region of Uganda, in eastern Africa. It was first identified in the US in the summer of 1999 in the Queens borough of New York, NY. It caused 62 cases of encephalitis and 7 deaths that summer. Since 1999 the virus has spread throughout the continental US and as of September 2002 has been identified in 42 states.
Mosquitos carry the highest amounts of virus in the early fall, thus there is a peak of disease in late August-early September. The risk of disease then decreases as the weather becomes colder and mosquitos die off.
Although many people are bitten by mosquitos that carry West Nile virus, most do not know they've been exposed. Few people develop severe disease or even notice any symptoms at all.
Data from the outbreak in Queens suggests that although 2.6% of the population was infected, only 1 in 5 infected people developed mild illness, and only 1 in 150 infected people developed brain inflammation (meningitis or encephalitis).
Risk factors for developing a worse form of the disease likely include the following:
- Conditions that suppress the immune system
- Pregnancy
- Older age
West Nile virus may also be spread through blood transfusions and organ transplantation. It is possible for an infected mother to transmit the virus to her child via breast milk.
Today's Top News Stories | • | Falls Are Top Cause of Injury, Death Among Elderly - Jul 19, 2008, 09:00
Not all homes are the same, but common sense measures can reduce the risk, expert says. | • | Heart Blood Vessels Grown in the Lab - Jul 18, 2008, 19:00
Could offer a future alternative to bypass surgery, researchers say. | • | Clinical Trials Update: July 18, 2008 - Jul 18, 2008, 09:24
- Breast Cancer
- Hot Flashes
- Emphysema
| • | Loud Music in Bars Hastens Drinking - Jul 18, 2008, 16:00
French researchers say blasting tunes makes patrons down more alcohol in less time. | • | Breast-Fed Babies Have Fewer GI Infections - Jul 18, 2008, 17:00
But they're more likely to be iron-deficient, study finds. |
|
Jump to another section
• Definition
• West Nile Virus Overview, Causes, & Risk Factors
• West Nile Virus Symptoms & Signs
• West Nile Virus Prevention
• West Nile Virus Diagnosis & Tests
• West Nile Virus Treatment
• West Nile Virus Prognosis
• West Nile Virus Complications
• Calling Your Health Care Provider
• Pictures & Images
Topics that might be of interest to you Diseases & Conditions
• Encephalitis
• Hepatitis C
• HIV Infection
• Meningitis
• Nonspecific Back Pain
• Poliomyelitis
Tests & Exams
• CBC
• Cranial CT Scan
• CSF Collection
• CSF Culture
• CSF Total Protein
• MRI of the Head
• Serology
• WBC Count
Other Topics
• Abdominal Pain
• Antibody
• Appetite - Decreased
• Chemotherapy
• Confusion
• Consciousness - Decreased
• Diarrhea
• Fever
• Headache
• Immunizations - General Overview
• Joint Pain
• Muscle Aches
• Nausea and Vomiting
• Rashes
• Sore Throat
• Weakness
Review Date : 11/7/2002
Reviewed By : Camille Kotton, M.D., Infectious Diseases Division, Massachusetts General Hospital and Brigham and Women's Hospital, Boston, MA. Review provided by VeriMed Healthcare Network.
|
|
