Salivary diagnostic tests can detect viral infections by identifying viral DNA and RNA, antigens, and antibodies. Antibody-based screening assays are used for the diagnosis of HIV, and saliva is an effective source for the Western blot test or polymerase chain reaction. The detection of hepatitis virus relies on the detection of antibodies, and saliva-based diagnostic tests have been designed for the detection of human papillomavirus. The salivary secretions also contain salivary proteins with effective anti-infective activity. The detection of viruses such as the dengue virus and human herpesvirus-6 (HHV-6) or human cytomegalovirus is more sensitive in saliva than blood. Measles virus-specific IgM was detected in saliva, providing a suitable noninvasive method for routine clinical use. There are many other viruses that can be detected in saliva and used for diagnostic purposes. For example, the Zika virus can be detected in saliva during the early stages of infection and can be used to diagnose Zika virus infection with high accuracy. Salivary diagnostic tests have also been developed for the detection of the influenza virus, respiratory syncytial virus (RSV), and human papillomavirus (HPV), among others. Therefore, salivary diagnostic tests have the potential to provide an easier and faster way to diagnose viral infections.