DR. MIELKE: Dr. Davis, would you please open this morning's discussion by commenting on the person who is infected with HIV but escapes present-day screening techniques: the so-called "window" period.
DR. DAVIS: This so-called "window" period that you refer to has only been found in a very small percentage of individuals infected with HIV. They usually have a history of very frequent sexual encounters or exposures. In any event, I don't think we're talking about a large population of people. There has now been the development of techniques that, rather than just identifying the antibody to the virus, are able to detect the virus itself, such as the PCR technique that has previously been described. I think that increasingly these techniques will probably be used together with the antibody tests on people who are considered to be high risk. At the present time I don't know how significant a risk this presents to the blood supply. Perhaps Dr. Allain has further comments in terms of the incidence of the presence of the virus before antibody? DR. ALLAIN: Clearly, most infected individuals who are going through the initial phases of infection either don't have clinical symptoms, so they are not recognized at all, or have flu-like clinical symptoms, but they are not identified as being related to HIV. What was actually found were a few cases who came to the hospital with a flu-like syndrome that was treated like an ordinary flu and didn't improve. So, the patients returned to the hospital and they were investigated further, and the diagnosis was made. So, I think the flu-like syndrome as an indication of HIV infection is much more common than one might think, but it is not recognized.
If we speak of this phenomenon in virological terms, what we are describing is the presence of HIV antigen and a high level of viral particles in circulation at the time preceding seroconversion. This phenomenon is probably present in everybody. But, the situation in which it can be recognized is fairly rare. So, I think that it is a general phenomenon, rarely recognized because it doesn't look like anything special.