Low B12 levels give rise to elevated homocysteine levels with an associated increased risk of many illnesses, including stroke and heart disease, without any classical B12 deficiency symptoms.

B12水平低引起同型半胱氨酸水平升高与许多疾病有关，包括中风和心脏病风险的增加，没有任何标准的B12缺乏症状。

youdao

Our findings are striking in that they show that these neighborhood factors can predict underlying heart disease in people without symptoms, as early as middle age.

我们的发现在显示这些地区因素可以预测早在中年时期人们没有症状的潜在心脏病方面是引人注目的。

youdao

Relieving or soothing the symptoms of a disease or disorder without effecting a cure.

治标的，不治本的用以减缓疾病或小病的征兆的，不受影响治疗。

youdao

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

VOA: special.2010.01.04

Although thermal scanners used in airports may detect travelers with symptoms, they are not effective since people exposed to an infectious disease could travel without any signs or symptoms and yet still be infectious.

CNN: Commentary: Flu and your health on a plane

Because the disease can persist for decades without symptoms, many Americans who are chronically infected are unaware of their infection status.

WHITEHOUSE: Presidential Proclamation -- World Hepatitis Day, 2012

Instead, researchers use these so-called natural-history studies to gain a better understanding of how the disease progresses without treatment and to track different symptoms.

WSJ: Families Push for New Ways to Research Rare Diseases