Severe fever with thrombocytopenia syndrome (SFTS) is a newly discovered emerging infectious disease that has recently become epidemic in Asia. The causative agent of SFTS is a novel phlebovirus in the family Bunyaviridae, designated SFTS virus (SFTSV). SFTS clinically presents with high fever, thrombocytopenia, leukocytopenia, gastrointestinal disorders, and multi-organ dysfunction, with a high viral load and a high case-fatality rate. In human infection, SFTSV targets microphages, replicates in the spleen of infected mice, and causes thrombocytopenia and a cytokine storm. The tick disseminates virus to humans and animals, forming a special transmission model in nature. Person-to-person transmission though direct contact with patient blood has been frequently reported. Measurements of viral RNA and antibodies have been established for diagnosis, but vaccines and specific therapeutics are not available so far.