In this book, various methods for detection of infectious diseases in humans and other organisms are described. These include polymerase chain reaction (PCR) technology, loop-mediated isothermal amplification (LAMP), and recombinase polymerase amplification (RPA). Each method presents different strengths and weaknesses and varies by sensitivity, specificity, and rapidity, among other characteristics. These techniques can be used for the detection of pathogens like SARS-CoV, MERS-CoV, SARS-CoV-2, influenza, lymphocystis disease virus, swine acute diarrhea syndrome coronavirus, swine vesicular disease virus, classical swine fever virus, infectious bursal disease virus, Marek’s disease virus, human papillomaviruses, infectious bronchitis virus, Newcastle disease virus, sacbrood virus, beak and feather disease virus, foot-and-mouth disease virus, bovine herpesvirus-1, and more. Other applications of these methods include molecular diagnosis of cancer, identification of genetically modified organisms, and detection of food adulteration.