Understanding how infectious diseases spread in the past is important to understanding how they affect populations today. The difficulty lie in piecing together information given that so little is known about how microbes spread historically. Applying academic rigor with scientific assessment, two microbiologists teamed with an archaeologist to look at different types of evidence — genetics, anthropology, paleontology and climate — in an attempt to explain how the fungus that causes Valley fever, Coccidioides immitis, ended up in a specific area of Washington state. The review article in mBio by Drs. David Engelthaler, James C. Chatters and Arturo Casadevall details their approach from a historical perspective, applying what they knew about the biology and epidemiology of C. immitis, which led them to propose a new theory for why it has emerged in that region of Washington. Today, a great deal of discussion around the spread of diseases and the expansion of their habitats focuses on the effects of global warming. And while climate change does have an impact on different environments and habitats, this investigation sought to understand how and why different microbes, like fungi, move from one place to another through the lens of modern biology. Their final analysis, climate change may not always be the reason behind the spread of diseases, but it can reveal past events that could be dangerous. Engelthaler explains more in this edition of TGen Talks.