Toward the end of the 20th century, deadly microbes seemed to be springing up out of nowhere: Lassa virus in 1969, Ebola virus in 1976 and HIV in the 1980s. Public health officials classified them as “emerging diseases,” meaning they are newly introduced or rising rapidly in human populations. Recent data, however, suggest these viruses may instead have been circulating widely for hundreds or thousands of years. We may not be contending with emerging disease at all, but emerging diagnosis of ancient and frequent disease. This paradigm shift has implications towards countering these viruses now before they become global threats.