Human Infection with Novel Spotted Fever Group Rickettsia Genotype, China, 2015

Abstract

Only 4 species of spotted fever group rickettsiae have been detected in humans in China. However, phylogenetic analysis of samples from 5 ill patients in China indicated infection with a novel spotted fever group Rickettsia, designated Rickettsia sp. XY99. Clinical signs resembled those of severe fever with thrombocytopenia syndrome.

Keywords: China; Spotted fever group rickettsiae; human infection; rickettsia; rickettsiosis; ticks; vector-borne infections.

Figure 1

Phylogenetic analyses based on nucleotide sequences of the outer member protein A (307-bp) (A) and citrate synthase (1,150-bp) (B) genes of Rickettsia. Boldface indicates the newly discovered Rickettsia genotype (Rickettsia sp. XY99). Asterisks after taxon names indicate that the sequence of Rickettsia species was found in China. Neighbor-joining trees were conducted by using the maximum composite likelihood method by means of MEGA version 5.0 (http://www.megasoftware.net). Bootstrap analysis of 1,000 replicates was applied to assess the reliability of the reconstructed phylogenies. Scale bars indicate estimated evolutionary distance.

Figure 2

Dynamic changes of 6 laboratory parameters (with 2-day intervals) during hospitalization of 5 patients with Rickettsia sp. XY99 infection, China, 2015. Red, patient 1; yellow, patient 2; green, patient 3; purple, patient 4; gray, patient 5. ALT, alanine aminotransferase, reference range 0–40 U/L; AST, aspartate aminotransferase, reference range 0–40 U/L; CK, creatine kinase, reference range 25–200 U/L; LDH, lactate dehydrogenase, reference range 109–245 U/L; platelets, reference range 100–300 × 10⁹/L; leukocytes, reference range 4.0–10.5 × 10⁹ cells/L.