evidence: Even the much stranger and more esoteric "terrain theory" seems to be making a modest comeback in alternative online spaces; the idea is that germs don’t cause illness in a healthy person whose "terrain" is sound thanks to vitamins, exercise, and sunlight. [...] By trying to effectively decouple cause and effect—claiming that HIV doesn’t cause AIDS, that measles isn’t caused by a virus and is instead a vitamin deficiency or caused by the MMR (measles, mumps, and rubella) vaccine itself—these movements discourage people from treating or trying to prevent serious and contagious illnesses. They try to sow doubt about the very nature of viruses themselves, a global gesture toward doubt, distrust, and minimization of serious diseases. Even the much stranger and more esoteric "terrain theory" seems to be making a modest comeback in alternative online spaces; the idea is that germs don’t cause illness in a healthy person whose "terrain" is sound thanks to vitamins, exercise, and sunlight.