Encephalitis: Viral - Highlights

Highlights

West Nile Virus Statistics

In 2006, 4,180 cases of West Nile virus were reported to the U.S. Centers for Disease Control. States with the highest number of reported cases included Idaho, Colorado, Texas, California, and Nevada. Of the reported cases, 61% were due to West Nile fever and 34% were due to West Nile neuroinvasive disease (encephalitis and meningitis). However, most cases of West Nile virus produce no symptoms and are not reported to state health authorities.

Long-Term Outcomes of West Nile Virus

Overall, about 20% of people who contract West Nile virus develop West Nile fever, and 1% develop neuroinvasive disease. West Nile fever is considered a less serious complication of West Nile virus than neuroinvasive disease. However, according to a 2006 study, both illnesses can produce similar long-term health problems. Researchers found that a year after being diagnosed with a West Nile infection, half of patients experienced fatigue, memory problems, headaches, depression, and tremors.

Pregnancy and West Nile Virus

Most pregnant women who contract West Nile virus do not experience birth complications and deliver healthy babies, indicates a 2006 study in Pediatrics.

Childhood Vaccines and Encephalitis

Standard childhood immunizations for measles-mumps-rubella (MMR) and diphtheria-pertussis-tetanus (DPT) do not increase the risk for encephalitis, according to a 2006 study in the Pediatric Infectious Diseases Journal.

Cerebrospinal Fluid Tests

Cerebrospinal fluid tests help diagnose encephalitis, including the type caused by West Nile virus. However, according to a 2006 study in Neurology, these tests cannot help predict the severity of West Nile virus encephalitis. The researchers found that older age was, however, a predictor of poorer outcome.

Review Date: 01/18/2007
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital