APPENDIX II-BI: CDC, WNV Life-Long Immunity and Testing for Immunity (IgG Antibodies).

This appendix is taken from two websites the first is:

http://www.cdc.gov/Ncidod/dvbid/westnile/qa/transmission.htm

West Nile Virus, CDC, Questions and Answers.

Q. How long does the West Nile virus remain in a person=s body after they are infected?

A. There is no scientific evidence indicating that people can be chronically infected with West Nile virus. What remain in a person=s body for long periods of time are antibodies and Amemory@ white blood cells (T‑lymphocytes) that the body produces to the virus. These antibodies and T‑lymphocytes last for years, and may last for the rest of a person=s life. Antibodies are what many diagnostic tests look for when clinical laboratories testing is performed. Both antibodies and Amemory@ T‑lymphocytes provide future protection from the virus.

Q. If a person contracts West Nile virus, does that person develop a natural immunity to future infection by the virus?

A. It is assumed that immunity will be lifelong, however, it may wane in later years.

The second half of this appendix is taken from:

http://www.nyc.gov/html/doh/html/wnv/wnvs2000.shtml

West Nile Virus

Questions & Answers on Serosurvey 2000

January 2001

The US Centers for Disease Control (CDC) and the New York City Department of Health (NYCDOH) announced on January 25, 2001 the results of the door‑to‑door WNV survey of households on Staten Island that took place in October 2000. The survey was conducted by NYCDOH with the assistance of the CDC to help estimate the percentage of people who were infected with the virus, and what their symptoms were, if any. Similar surveys also took place in the fall of 2000 in Suffolk County, New York, and Fairfield County, Connecticut. A summary of findings from these surveys appears in the January 26, 2001, issue of the CDC's Morbidity and Mortality Weekly Report.....

Q. Are people who tested positive still at risk from West Nile virus?

A. No. The infection (and any associated illness) is short‑lived. A person with antibodies to West Nile virus is likely to have life‑long immunity to a repeat infection of this virus.

Q. What tests were conducted on the blood and why?

A. Serum samples were tested for two types of antibodies to WNV: immunoglobulin M (IgM) and immunoglobulin G (IgG). These two tests help determine whether an individual was recently infected with WNV (IgM antibodies) and whether an individual was ever infected with WNV (IgG antibodies)….