Human infection with Candidatus Rickettsia tarasevichiae.

n engl j med 369;12 nejm.org september 19, 2013 1178 325-bp ompA sequences revealed that the agent clustered with other R. sibirica subspecies and was most closely related to R. sibirica subspecies sibirica 246, which had been isolated from Dermacentor nuttalli in Russia (Fig. 1). In serum samples obtained from the patient, the titers of IgM and IgG antibodies against R. sibirica on indirect immunofluorescence assay increased from 1:32 and 1:64, respectively, in the acute phase to 1:4096 for IgM and for IgG in the convalescent phase. The study of this case was approved by the institutional review board of the Chinese Academy of Military Medical Sciences. The patient provided written informed consent. R. sibirica subspecies sibirica BJ-90 was initially isolated from D. sinicus in China in 1990,2,3 and it was detected in D. silvarum in Russia.4 Our case shows that this organism can cause human disease. Unlike patients infected with R. sibirica and R. heilongjiangensis in the same geographic region,5 this patient was severely ill with multiorgan dysfunction. Further investigation of the epidemiologic and clinical features of R. sibirica subspecies sibirica BJ-90 is required to distinguish it from other known tickborne infections.