A cluster of cases of human-to-human transmission caused by severe fever with thrombocytopenia syndrome bunyavirus.

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease in six epidemic provinces of China and was identified to be caused by a novel bunyavirus in 2009. It is progressive in nature and potentially fatal. SFTS usually occurs as sporadic cases and is considered a tick-transmitted disease. Here we present a group of three patients with proven SFTS and one with probable SFTS, for whom the epidemiological data show person-to-person transmission characteristics. The index patient and two secondary patients died. None reported a tick bite.