liz@ai.mit.edu (Liz A. Highleyman) (01/16/91)
I was under the impression that the time between infection with HIV and the development of illness was somewhere in the area of 5 years. Yet I have also heard that people who received transfusions of infected blood (early in the epidemic) were known to get sick within a few months. How can this be? Is it taking longer and longer for people to develop OIs? Does this indicate that HIV is perhaps becoming less virulent? -Liz
winters@pdn.paradyne.com (John Winters) (01/16/91)
If you get blood from an AIDS patient, you are getting many more of the virus than the one or two you would get otherwise. Of course, this puts you into a more advanced condition at the onset. That is why it does not need to take as long.
rob@mtdiablo.Concord.CA.US (Rob Bernardo) (01/17/91)
In article <1991Jan15.174741.14099@cs.ucla.edu> liz@ai.mit.edu (Liz A. Highleyman) writes: >I was under the impression that the time between infection with HIV and >the development of illness was somewhere in the area of 5 years. A significant number of people have been infected but not ill for 10 years. > Yet >I have also heard that people who received transfusions of infected >blood (early in the epidemic) were known to get sick within a few months. >How can this be? They got a relatively large "dose" of the virus? > Is it taking longer and longer for people to develop >OIs? Improved treatments is probably a huge factor here. > Does this indicate that HIV is perhaps becoming less virulent? There is evidence that differing strains have differing virulence. (This is a big reason why people who are already infected should engage in safe sex even with each other: to protect against getting infected by a more virulent strain of HIV.) -- Rob Bernardo Mt. Diablo Software Solutions email: rob@mtdiablo.Concord.CA.US phone: (415) 827-4301
dgreen@uunet.UU.NET (01/17/91)
liz@ai.mit.edu (Liz A. Highleyman) writes: |> I was under the impression that the time between infection with HIV and |> the development of illness was somewhere in the area of 5 years. Yet |> I have also heard that people who received transfusions of infected |> blood (early in the epidemic) were known to get sick within a few months. |> How can this be? Is it taking longer and longer for people to develop |> OIs? Does this indicate that HIV is perhaps becoming less virulent? I had the opportunity to interact with a mathematical epidemiologist this summer: she estimated the time from exposure to full-blown AIDS has a standard half-life of about 8-10 years. This means that at 8 years, half of the people exposed will have contracted full-blown AIDS. At 16 years, 3/4 will have contracted full-blown AIDS, etc. I know of no documentation indicating that HIV is becoming less virulent. It makes sense that a person who received a massive infusion of infected blood might take less time to contract the full disease, than one who was exposed through some other, less efficient transmission mode. Furthermore, in the beginning years of the epidemic, no testing was done of donated blood, so the likelihood of getting a transfusion containing a raging infection might be higher. Finally, however, it is a good rule of thumb that over many years, fatal infectious agents evolve to something less virulent: from an evolutionary standpoint, it isn't good policy to kill one's host. However, the number of years required to see this evolution will likely be large, especially in the case of HIV, which already takes a very long time to kill the host. ____ \ /Dan Greening IBM T.J.Watson Research Center NY (914) 784-7861 \/ dgreen@ibm.com Yorktown Heights, NY 10598-0704 CA (213) 825-2266
aberno@questor.wimsey.bc.ca (Anthony Berno) (01/20/91)
liz@ai.mit.edu (Liz A. Highleyman) writes: > I was under the impression that the time between infection with HIV and > the development of illness was somewhere in the area of 5 years. Yet > I have also heard that people who received transfusions of infected > blood (early in the epidemic) were known to get sick within a few months. > How can this be? Is it taking longer and longer for people to develop > OIs? Does this indicate that HIV is perhaps becoming less virulent? > > -Liz Actually, the time from infection to the onset of noticeable symptoms averages almost 8-10 years! I read a number of articles on the subject that discussed the onset time of the disease - for a person infected "today", symptoms will take an average of about 10 years to appear. The typical scenario is that nothing happens for two years, then T-cell counts drop from their normal 1000 by about 100 per year. When the counts hit about 200, you start to get sick. Curiously, there is a little statistical anomaly in that the average person developing AIDS today was infected only 6-7 years ago. This is due to the skewed profile of the epidemic (well, ALL epidemics are like that...) i.e. most people infected with HIV were infected recently, so that those that deveop the disease early are disproportionatly represented. Keep in mind that HIV is not a carefully timed clock - as always, some people will develop the disease immediately, others will take many many years. I have heard of no difference correlated with the mode of infection, but then I have been a little out of touch. Sorry, I can never remember my sources for my statistics. I think the above ones were from a March issue of Science?