Two strains of the disease, with almost identical symptoms, affected humans—Ebola-Zaire and Ebola-Sudan.

两种具有几乎相同的症状的疾病感染了人类——扎伊尔埃博拉病毒和苏丹埃博拉病毒。

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Ocular form: In this form of the disease, the usual symptoms associated with the mild form of the disease are accompanied by retinal lesions.

眼部反应：出现这种疾病反应时，与轻度疾病反应有联系的通常症状伴有视网膜病变。

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Chronic fatigue is a classic MUPS (medically unexplained physical symptoms) disease, with a diagnosis based only on the ruling out of other possibilities.

慢性疲劳是一种典型的MUPS(即无法以医学的方式解释的躯体症状)疾病，对它的诊断仅仅只是排除了其他疾病的可能。

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People infected with this form may develop the disease over many years without any major symptoms.

VOA: special.2010.01.04

It says it is using the latest world-class diagnostic tests to look for the disease in patients with symptoms.

BBC: Areas of woodland can harbour ticks

Adding to the uncertainty: Lupus is a notoriously slippery disease, with highly unpredictable symptoms, making trials difficult.

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The detection of Alzheimer's disease in people with no symptoms is very much a work in progress, said Dr. Allan Levey, professor and chair of neurology at Emory University Medical School.

CNN: Children of Alzheimer's sufferers want to know their risk