Evolution of infectious disease: A biocultural analysis of AIDS.

Abstract

The evolution of infectious disease can be understood from an ecological model that incorporates information from anthropology, epidemiology, and biomedicine. This model considers variables such as the pathogen, the host population, and the environment. In this model, the role that culture as well as other environmental variables plays in the transmission of infectious disease in human populations is considered. In addition, the sociocultural response and its impact on the disease process can be analyzed. The present AIDS epidemic is placed in an ecological and evolutionary context of the disease in hominid evolution. The interaction between Human Immunodeficiency Virus (HIV) and human populations is considered in this perspective. The ability of the virus to survive in semen and blood both increases as well as limits the possibility of transmission. Cultural practices that increase the transmission of blood and semen or increase sexual activity will obviously increase the potential risk of viral transmission. In societies that practice exchange of blood, blood transfusion, and where vaccinations with unclean needles exist or where there is intravenous (IV) drug use, the transmission of HIV by blood is enhanced. HIV which can cause a breakdown of the immunological system is paradoxically a very fragile pathogen. Replication occurs within T-cells, an important part of the immunological system. Outside of the blood or semen the virus dies quickly. From the perspective of the pathogen's adaptation, the virus has effectively solved the problem of survival. The fragile virus's long incubation period and its ability to survive in the presence of antibodies help to assure its transmission. HIV's ability to suppress the immunological system may assure its immediate survival, but this adaptation may cause the death of its host from other opportunistic pathogens that are usually not lethal.