Chimpanzee (from Darwin)
Disappointed chimpanzee” – J.M. Wood (from Darwin,
“The expression of the emotions in man and animals”, 1872)

Untreated HIV has very, very high mortality, but there are a few people who manage to survive for quite a long time without progressing to AIDS. These long-term non-progressors somehow keep their HIV levels quite low, and it was thought they wouldn’t develop the disease.  But:

Low-level viremia is present in the majority of elite controllers and is associated with higher HIV-1–specific antibody responses. Absolute CD4+ T cell loss is more common among viremic individuals, suggesting that even very low-level viremia has negative consequences over time.1

So, even among these apparently-resistant people, there’s still a trend (albeit a slow trend) toward immune deficiency.

HIV is essentially simian immunodeficiency virus (SIV) that’s crossed over into humans.  Several non-human primates naturally have SIV circulating among them, and it’s usually said that in the natural hosts SIV in not harmful.  But:

SIVcpz has a substantial negative impact on the health, reproduction and lifespan of chimpanzees in the wild. … SIVcpz-infected chimpanzees in Gombe have a 10–16-fold increased death hazard compared to uninfected chimpanzees … SIVcpz infection is associated with progressive CD4+ T-cell loss and immune system destruction, which are hallmarks of pathogenic HIV-1 infection. … SIVcpz seems to be less pathogenic than HIV-1, but more pathogenic than HIV-2 and SIVsmm.2

So, even among this apparently-resistant species, there’s still a trend toward immune deficiency.


  1. Pereyra, F., Palmer, S., Miura, T., Block, B., Wiegand, A., Rothchild, A., Baker, B., Rosenberg, R., Cutrell, E., Seaman, M., Coffin, J., & Walker, B. (2009). Persistent Low?Level Viremia in HIV?1 Elite Controllers and Relationship to Immunologic Parameters The Journal of Infectious Diseases, 200 (6), 984-990 DOI: 10.1086/605446[]
  2. Keele, B., Jones, J., Terio, K., Estes, J., Rudicell, R., Wilson, M., Li, Y., Learn, G., Beasley, T., Schumacher-Stankey, J., Wroblewski, E., Mosser, A., Raphael, J., Kamenya, S., Lonsdorf, E., Travis, D., Mlengeya, T., Kinsel, M., Else, J., Silvestri, G., Goodall, J., Sharp, P., Shaw, G., Pusey, A., & Hahn, B. (2009). Increased mortality and AIDS-like immunopathology in wild chimpanzees infected with SIVcpz Nature, 460 (7254), 515-519 DOI: 10.1038/nature08200[]