Tick-Borne Disease Presents In China With Apparent Human Transmission

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Main Category: Infectious Diseases / Bacteria / Viruses
Also Included In: Public Health;  Blood / Hematology;  Respiratory / Asthma
Article Date: 01 Dec 2008 - 0:00 PDT

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It appears that human ganulocytic anaplasmosis (HGA) has been identified in China for the first time, and was transmitted between two humans rather than ticks, according to a study published on November 19, 2008 in JAMA.

HGA, usually carried by ticks, and has symptoms similar to those of influenza. HGA has been noted in the United States since 1990 and Europe since 1997. The number of infections reported in the United States each year has been increasing, with previous studies indicating endemic infection rates as high as 15-36%. This relatively high prevalence implies that diagnosis may often be mild or asymptomatic, and thus misdiagnosed. "Because epidemiological, clinical, and microbiological information about HGA is limited, the disease is likely underrecognized and underreported worldwide," say the authors of the study.

Prompted by a cluster of cases among health care workers and their family members, Lijuan Zhang, M.D., Ph.D., of the National Institute of Communicable Disease Control and Prevention, China CDC, Beijing, and colleagues performed the study in which they investigated several subjects whose symptoms were consistent with those of HGA. They sought to determine the origin and transmission of these apparent first Chinese cases, specifically investigating the possibility of human-to-human transmission.

Between November 9 and 17 of 2006, nine patients with fever and other consistent symptoms were diagnosed with HGA. Curiously, while all nine patients had been in contact with another symptomatic, suspected HGA patient within 12 hours of her death, none bore tick bites.

The initially symptomatic patient, referred to as the index patient, suffered from a fatal illness characterized by fever and hemorrhage, and required endotrachial intubation, in which a plastic tube is inserted into the trachea, to ventilate the lungs at both a primary care hospital and regional tertiary care hospital's isolation ward. Inquiries to the family of the patient later revealed that she had been bitten by a tick 12 days before the symptoms presented.

Suspected secondary cases, who were exposed to the index cases, were tests for antibodies against the bacterium responsible for HGA, Anaplasma phagocytophilum, and potential exposure sources were further investigated. These patients indicated that they did not likely use gloves during or wash after contact with the index patient.

A total 28 individuals reported contact within 20 inches of the index patient in her final 12 hours, and 9 of these individuals were infected. A total 20 individuals reported exposure to the index patient for more than two hours, and 9 of these individuals were infected. All 9 total infected patients had made contact with blood, and seven had made contact with the index patient's respiratory secretions. Those persons, exposed to blood or respiratory secretions, especially those with pre-existing skin lesions or injuries, were more likely to be infected.

The authors note the unusual method of transmission for the bacterium. "The most remarkable aspect of these cases was that transmission was very unlikely to be tick-borne, but was closely associated with blood or respiratory secretion exposure from an index patient who died of a [sudden and severe] illness with hemorrhage," the authors write.

They conclude with recommendations for future prevention of this type of outbreaks. "Although it is likely that routine blood and body fluid precautions will protect against such future events, strict adherence to protective protocols is mandatory even if communicability is deemed unlikely. The lessons of this study remain relevant to the daily hospital and health care unit operations to prevent any additional [hospital] outbreaks of HGA. Moreover, as China advances into its future, it must also now become prepared to deal with the increasing threat that tick-borne rickettsial pathogens [parasitic bacteria that live in anthropods (as ticks and mites) and can cause disease if transmitted to human beings] have been already brought to the United States and Europe."

Peter J. Krause, M.D., of the Yale School of Medicine, New Haven, Conn., and Gary P. Wormser, M.D., of New York Medical College, Valhalla, N.Y., contributed an accompanying editorial, noting that these findings are an important reminder to follow safety precautions regarding disease transmission. They write: "What is the significance of the investigation by Zhang et al? It may represent the first report of human-to-human transmission of A phagocytophilum and the first report of human HGA infection in China. This report certainly serves to reinforce the importance of adopting standard blood and body fluid precautions for all patients and especially for those with HGA; these precautions are the accepted standard of care in the United States. The report also should stimulate further investigation of the existence of A phagocytophilum in the region of China where this outbreak originated. In addition, it is essential to emphasize that fulfilling the case definition of HGA used for epidemiological surveillance in the United States does not provide diagnostic certainty, unless the diagnosis was established by the microbiological gold standard of culturing the microorganism. Therefore, the findings of the study by Zhang et al, while interesting and provocative, should be regarded as preliminary."

Nosocomial Transmission of Human Granulocytic Anaplasmosis in China
Lijuan Zhang, MD, PhD; Yan Liu, MD; Daxin Ni, MD; Qun Li, MD; Yanlin Yu, MD; Xue-jie Yu, MD, PhD; Kanglin Wan, MD, PhD; Dexin Li, MD; Guodong Liang, MD; Xiugao Jiang, MD; Huaiqi Jing, MD; Jing Run, MD; Mingchun Luan, MD; Xiuping Fu, MD; Jingshan Zhang; Weizhong Yang, MD; Yu Wang, MD, PhD; J. Stephen Dumler, MD; Zijian Feng, MD; Jun Ren, MD; Jianguo Xu, MD, PhD
JAMA. 2008;300(19):2263-2270.
Click Here For Abstract

Nosocomial Transmission of Human Granulocytic Anaplasmosis?
Peter J. Krause, MD; Gary P. Wormser, MD
JAMA. 2008;300(19):2308-2309.

Written by Anna Sophia McKenney
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