Tissue samples have been used to reconstruct the 1918 influenza epidemic and to illuminate the proliferation of the AIDS virus.
Preserved human tissue can help shed light on why diseases — caused by microbes, environmental exposures and lifestyle changes — emerged when they did. It might even help scientists predict disease trends or outbreaks. Michael Worobey, an evolutionary biologist at the University of Arizona, is among the top researchers responsible for establishing the most credible date for when HIV entered the human population. He was able to do so in part thanks to analysis of tissue samples such as the ones pictured, from Congo, where some of the earliest HIV cases were discovered. The tissues are stored in blocks of wax. Michael Worobey/MICHAEL WOROBEY