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HIV jumped from apes to humans at least four times, as evidenced by genetically distinct groups of the virus that have been detected: M, N, O, and P. While N and P have had little impact, M is responsible for the pandemic affecting millions of individuals, and O has infected another 100,000.

This interrupted case study for the flipped classroom applies evolutionary genetics research to human health. Students learn about a naturally occurring, but rare, allele of the CCR5 gene, CCR5-Δ32, which provides resistance to HIV. They use data from primary literature sources to predict and interpret worldwide patterns of CCR5-Δ32 frequency distribution. They then discuss how these allele frequency patterns may have been driven by selection imposed by various diseases or by other evolutionary mechanisms. Next, they test published data using Hardy-Weinberg equilibrium to examine if CCR5-Δ32 also provides genetic resistance to West Nile virus. Finally, they complete a jigsaw discussion of Nature News articles that report on how CCR5 research is being used to develop therapies to treat HIV. Originally written for the evolution portion of a yearlong biology series for undergraduate majors, the case is also appropriate for some non-majors biology courses or, with added complexity, upper-level evolution, genetics, or cell biology courses.

Emerging diseases and potential pandemics make the news nearly every year. Students (and everyone else) may wonder where new infectious diseases come from, how scientists assess the risk of a pandemic, and how we might go about preventing one. This case study uses a PowerPoint presentation to explore these questions by focusing on HIV, a pandemic that began as an emerging disease. The storyline progresses backwards through time as scientists attempt to unravel the origins of a new, mysterious plague. Much of the case relies on audio excerpts from an episode produced by Radiolab, an acclaimed radio show that explores a variety of topics in science and culture (www. radiolab.org). Students use graphics, animations, and sound clips presented in the PowerPoint slides to discuss several sets of questions. The case is suitable for a wide range of high school and college introductory biology courses, as well as undergraduate microbiology, ethics, and public health courses.