Human-to-Human Transmission of Severe Fever With Thrombocytopenia Syndrome Bunyavirus Through Contact With Infectious Blood

We investigated an outbreak of severe fever with thrombocytopenia syndrome (SFTS) that occurred during May and June 2010, to identify the mode of transmission. Contact with the index patient's blood was significantly associated with development of SFTS (P = .01, by the chi(2) test for linear trend); the frequency of contact with the index patient's blood increased the risk of SFTS in a dose-response manner (P = .03, by the chi(2) test for linear trend). We concluded that human-to-human transmission caused this cluster of cases.