I am working on mathematically modeling HIV and Tuberculosis Co-infection dynamics, and am working with 12 differential equations describing the behavior of all of the compartments and parameters.

Anyway, I just have one question:

Which is harder, in general: For a susceptible person to contract HIV, or a HIV+ person to contract AIDS?

Please pardon my ignorance.


  • $\begingroup$ infection rate constant is much higher than disease progression constant. The rates will depend on how many infected individuals are present and how much are they interacting.. $\endgroup$ – WYSIWYG Nov 1 '13 at 7:15
  • $\begingroup$ This is rather broad... $\endgroup$ – Amory Nov 1 '13 at 13:24

Your question depends hugely on the factors at play.

  • The rate of transmission depends on the route of infection. Wikipedia has a good breakdown showing the wide variability. Are they getting a blood transfusion? 90%. Mother-to-infant? 25%. Male-to-female vaginal sex? No higher than 0.3%. Not to mention that the incidence varies massively between countries, as does the most common route of infection.
  • The rate of progression to AIDS also depends on a large number of factors including age, viral load, various genotypes, access to medical treatment, and, of course, long-term nonprogressor (LTNP) status.

The incidence of LTNPs is around 1 in 500, or 0.2%, which overlaps with but is at the low end of transmission rates for some routes of infection.

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