West Nile virus is a disease spread by mosquitos. The condition ranges from mild to severe.
Causes, incidence, and risk factors
West Nile virus was first identified in 1937 in Uganda in eastern Africa. It was first discovered in the United States in the summer of 1999 in New York. Since then, the virus has spread throughout the United States.
The West Nile virus is a type of virus known as a flavivirus. Researchers believe West Nile virus is spread when a mosquito bites an infected bird and then bites a person.
Mosquitos carry the highest amounts of virus in the early fall, which is why the rate of the disease increases in late August to early September. The risk of disease 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.
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 what part of the body is affected.
Risk factors for developing a more severe form of West Nile virus include:
Conditions that weaken the immune system, such as HIV, organ transplants, and recent chemotherapy
West Nile virus may also be spread through blood transfusions and organ transplants. It is possible for an infected mother to spread the virus to her child through breast milk.
Insect bites and stings (26 images)(Doctor-Reviewed information)
Insect bites and stings can cause an immediate skin reaction. The bite from fire ants and the sting from bees, wasps, and hornets are usually painful. Reviewer: John E. Duldner, Jr., MD, MS, Assistant Professor of Emergency Medicine, Director of Research, Department of Emergency Medicine, Akron General Medical Center and Northeastern Ohio Universities College of Medicine. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.Date: 02/19/2008
Encephalitis(Doctor-Reviewed information)
Encephalitis is irritation and swelling(inflammation) of the brain, usually due to infections.Encephalitis is most often caused by a viral infection. Many types of viruses may cause it. Reviewer: Jatin M. Vyas, PhD, MD, Instructor in Medicine, Harvard Medical School, Assistant in Medicine, Division of Infectious Disease, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.Date: 09/28/2008
Meningitis (6 images)
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(Doctor-Reviewed information)
Meningitis is swelling and irritation(inflammation) of the membranes covering the brain and spinal cord. This inflammation causes changes in the cerebrospinal fluid(CSF) that surrounds the brain and spinal cord.The most common causes of meningitis...Reviewer: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; and Jatin M. Vyas, PhD, MD, Instructor in Medicine, Harvard Medical School, Assistant in Medicine, Division of Infectious Disease, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.Date: 09/28/2008
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