9/23 Response to Lecture on Biology and Epidemiology of HIV/AIDS

The distinction between HIV/AIDS "prevalence" rates and "incidence" rates made by Professor Thairu struck me as incredibly important, particularly as these statistical terms relate to the differences in the epidemiology of AIDS in various countries. The difference between these two terms seems to create a situation in which HIV/AIDS statistics, which are already difficult to accurately obtain, can ultimately misrepresent the status of the epidemic in a particular area. As we discussed in class, the prevalence of HIV/AIDS can drop while the incidence remains the same. The behavioral, social, economic and biological factors affecting the pattern of HIV/AIDS epidemics are already incredibly numerous and complex, as Iliffe discusses in his analysis of the spread of the African epidemic. Thus, the fact that prevalence can decrease while incidence remains the same introduces yet another variant into the cause and effect relationship between HIV/AIDS risk factors and the spread of the epidemic. Are AIDS deaths responsible for drops in prevalence in, for instance, eastern Africa? Or are treatment and prevention plans experiencing enough success to result in a decline in both prevalence and incidence rates? Furthermore, it is obviously very difficult to assess how accurate HIV/AIDS statistics are, due to the impossibilities of testing entire populations. If more accurate data were available, would comparative statistics between various countries change, resulting in changes in public health policy and international aid distribution for HIV/AIDS?

As several other students noted, I was also struck by the diversity of the epidemic. I was aware that HIV had various subtypes; however, I was not aware of the biological implications of this variation in terms of transmission and virulency. Iliffe discusses the patterns of subtype C in Ethiopia in contrast with the prevalence of subtypes A and D in the majority of eastern Africa (pg. 30), and I was struck by how the existence of various subtypes introduces yet another factor in the search for explanations as to where the epidemic exploded, and where it stayed relatively stable. In general, both Professor Thairu's lecture and Iliffe's reading highlighted the importance of statistics in studying HIV/AIDS yet also cautioned against relying too heavily on statistics, as available data may not always present the most complete picture of the behavior of the epidemic.