Dr. Bob,

first let me say that I highly admire you and like you, your wit is a real gift.

Im an educational psychologist and lecture teens about HIV and other sexual issues.

you mentioned in one of your answers that there were "wimpy" and more "agrsiive" strains of HIV, I generally know that HIV1 is less agressive than HIV2, but I wish you could elaborate on that,the diference on strains, as some teens are asking questions on this respect, and I need to be highly informed in any question I answer, as I dont want to disinform.

I highly apreciate your response, as my next talk is due next week.

regards, counselor Alejandro , from Mexico.

Hello Alejandro,

A thorough discussion of this topic is beyond the scope of this forum. However, you can find additional details on this topic by reviewing the archives and related links. The basic message is that HIV transmission, as well as the rate of HIV disease progression, depends on many different variables, including viral factors (different viral strains and subtypes, for instance) and host immune factors (the strength and effectiveness of a particular person's immune system). Regarding viral factors for example, different viral strains can utilize different mechanisms to infect and/or destroy CD4 cells.

I should also clear up one other point from your post. HIV-2 is less transmissible (0.5- to 8-fold less efficient than HIV-1) and is associated with lower viral loads and slower rates of CD4 cell decline as well as slower rates of clinical progression. Consequently, HIV-2 would be considered less aggressive than HIV-1.

Dr. Bob