Context: Human granulocytic anaplasmosis (HGA) is an emerging tick-borne disease in China. A cluster of cases among health care workers and family members following exposure to a patient with fulminant disease consistent with HGA prompted investigation. Objective: To investigate the origin and transmission of apparent nosocomial cases of febrile illness in the Anhui Province. Design, Setting, and Patients: After exposure to an index patient whose fatal illness was characterized by fever and hemorrhage at a primary care hospital and regional tertiary care hospital's isolation ward, secondary cases with febrile illness who were suspected of being exposed were tested for antibodies against Anaplasma phagocytophilum and by polymerase chain reaction (PCR) and DNA sequencing for A phagocytophilum DNA. Potential sources of exposure were investigated. Main Outcome Measure: Cases with serological or PCR evidence of HGA were compared with uninfected contacts to define the attack rate, relative risk of illness, and potential risks for exposure during the provision of care to the index patient. Results: In a regional hospital of Anhui Province, China, between November 9 and 17, 2006, a cluster of 9 febrile patients with leukopenia, thrombocytopenia, and elevated serum aminotransferase levels were diagnosed with HGA by PCR for A phagocytophilum DNA in peripheral blood and by seroconversion to A phagocytophilum. No patients had tick bites. All 9 patients had contact with the index patient within 12 hours of her death from suspected fatal HGA while she experienced extensive hemorrhage and underwent endotracheal intubation. The attack rate was 32.1% vs 0% (P=.04) among contacts exposed at 50 cm or closer, 45% vs 0% (P = .001) among those exposed for more than 2 hours, 75% vs 0% (P<.001) among those reporting contact with blood secretions, and 87.5% vs 0% (P=.004) among those reporting contact with respiratory secretions from the index patient. Conclusion: We report the identification of HGA in China and likely nosocomial transmission of HGA from direct contact with blood or respiratory secretions.
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