Skip directly to search Skip directly to A to Z list Skip directly to navigation Skip directly to site content Skip directly to page options
CDC Home

This page is a historical archive and is no longer maintained.

For current information, please visit

Press Release

For Immediate Release: October 5, 1999
Contact: CDC Media Relations (404) 639-3286

West Nile-like Virus

  • CDC has confirmed West Nile-like virus as the cause of the human encephalitis outbreak among persons in New York.
  • CDC has confirmed West Nile-like virus in birds in New York City, New York State, Connecticut and New Jersey. The virus has also been confirmed in mosquitoes in New York City and Connecticut.
  • Federal, state, and local health officials continue to work closely together to investigate and control this outbreak of West Nile-like encephalitis in the New York area. All current control and prevention measures are the measures that should be taken for West Nile-like virus.
  • Most mosquito bites people experience are a nuisance, but will not transmit the West Nile virus. Most people who become infected with West Nile from a mosquito bite will not become ill or seriously ill. Control and prevention measures are working well and reports of illness are dramatically dropping. However, it's important that individuals continue to limit their exposure to mosquitoes.
  • A hard freeze will significantly reduce mosquito activity for this season, but until then, health officials encourage the public to follow recommendations to limit time outside at dawn, dusk and early evening when mosquitoes are feeding. If you must be outside, cover your skin with long sleeves and long pants and spray the outside of your clothing and exposed skin with mosquito repellent.
  • New York City Health Department, with the assistance of CDC, is conducting a simple community-based voluntary and anonymous "sero-prevalence survey." It's a typical tool of all disease detectives. It helps the community answer the question: "How many people who became infected with West Nile-like virus actually became ill?"
  • Since late August, New York City has been experiencing an outbreak of arboviral (mosquito-borne) encephalitis. Previously, diagnostic tests on serum from human cases in this outbreak were reported as St. Louis encephalitis virus infection. Both are genetically similar and cross reactivity occurs in the diagnostic tests for these infections. Further serologic tests confirmed West Nile-like virus infection in humans.
  • CDC is working with the U.S. Geological Survey's National Wildlife Health Center, Madison, Wis.; state wildlife agencies, and state and local health and vector control agencies to conduct surveillance of birds and mosquitoes that may be infected with West Nile-like virus in the United States.

Statement from the Director CDC, National Center for Infectious Diseases

West Nile Virus and the Emerging Infectious Diseases Plan

During CDC's outbreak investigation of arboviral (mosquito-borne) encephalitis in New York City, which began in late August, we reported the introduction of West Nile-like virus into the Western Hemisphere. One of the compelling questions in this investigation is, "How did this virus migrate to the Western Hemisphere, and the United States?" As interesting as this question may be, the answer may remain elusive--Mother Nature does not always reveal her secrets.

We live in a global village and we take every disease outbreak and every new or re-emerging disease very seriously. While we cannot expect to totally prevent the migration of viruses from one part of the world to another, our best efforts should, and do, concentrate on the steps outlined in the U.S. emerging infectious disease plan--strong surveillance for early detection and response, well-equipped labs and a cadre of public health officials trained and equipped to confront and control viruses.

Infectious diseases are a continuing menace to all people, regardless of age, gender, lifestyle, ethnic background, or socioeconomic status. They cause suffering and death, and impose an enormous financial burden on society. Although some diseases have been conquered by modern advances, such as antibiotics and vaccines, new ones are constantly emerging (such as AIDS, Lyme disease, and hantavirus pulmonary syndrome), while others reemerge in drug-resistant forms (such as malaria, tuberculosis, and bacterial pneumonias).

The emergence and re-emergence of diseases have been fueled by: worldwide population growth, behavior changes, international travel, worldwide transport of animals and food products, human encroachment on wilderness habitats and microbial evolution and their development of resistance to antibiotics and other antimicrobial drugs. Whatever the cause, the resurgence of diseases attributed to newly emerging microbes poses a continuing challenge.

Because we do not know what new diseases will arise, we must always be prepared for the unexpected. CDC's vision for the 21st century is of individuals, communities, and nations joined in a common effort to control today's emerging infectious diseases and to prevent those of tomorrow. To realize this vision, CDC scientists have designed a plan to respond to the emergence and resurgence of microbial threats in the new millennium -- Preventing Emerging Infectious Diseases: A Strategy for the 21st Century.

James M. Hughes, M.D
CDC, National Center for Infectious Disease

Sero-prevalence Survey: Outbreak Investigation Tool

  • An important question to answer during an outbreak is, "How many people who are infected become sick?" A "sero-prevalence survey" can help do that.
  • A voluntary community-based "sero-prevalence survey" is a typical tool of all disease detectives. "Sero" refers to the taking of a sample of blood through a needle stick. Prevalence is the status of infection or disease in a population at a point in time--how many people are infected. A survey is a statistical sample of a population.
  • A sero-prevalence survey helps answer the question: "How many people who become infected actually become ill?" In some disease outbreaks, healthy people may have been infected in the recent past and never became ill or only slightly ill. A sample of their blood will tell who was infected and did not become ill versus those who were infected and became ill.
  • Public health professionals often apply this tool during outbreak investigations when they expect that most people who become infected won't become ill. If we neglected to do these surveys, we would not be able to find out which people are most at risk for serious illness from disease-causing organisms.
  • Epidemiologists (disease detectives) use this tool often during other vector-borne, waterborne, and foodborne outbreaks in community settings.

West Nile-like Outbreak Investigation

  • Viruses like West Nile typically will not cause severe illness in most people who become infected from a mosquito bite.
  • The New York City health department is in charge of this survey. CDC is helping design the survey so the collective results help answer important public health questions. This is an important survey for the community.
  • Everyone who participates will be fully informed about what is required if they participate and how blood collected will be used. Everyone who participates must be a volunteer. This is an anonymous survey; no personal identifying information will be collected. Results will be available in a few months only as an aggregate report.
  • Public health professionals rely on the goodwill of community members to investigate an outbreak this way and will work hard to maintain this mutual good faith.


Contact Us:
  • Centers for Disease Control and Prevention
    1600 Clifton Rd
    Atlanta, GA 30333
  • 800-CDC-INFO
    TTY: (888) 232-6348
  • Contact CDC–INFO The U.S. Government's Official Web PortalDepartment of Health and Human Services
Centers for Disease Control and Prevention   1600 Clifton Road Atlanta, GA 30329-4027, USA
800-CDC-INFO (800-232-4636) TTY: (888) 232-6348 - Contact CDC–INFO
A-Z Index
  1. A
  2. B
  3. C
  4. D
  5. E
  6. F
  7. G
  8. H
  9. I
  10. J
  11. K
  12. L
  13. M
  14. N
  15. O
  16. P
  17. Q
  18. R
  19. S
  20. T
  21. U
  22. V
  23. W
  24. X
  25. Y
  26. Z
  27. #