without symptoms.

Merriam-Webster Online Dictionary
asymptomatic (adjective)
presenting no symptoms of disease
asymptomatic (Wikipedia)
Pulmonary contusion due to trauma is an example of a condition that can be asymptomatic with half of people showing no signs at the initial presentation since such symptoms can take time to develop. The CT scan shows a pulmonary contusion (red arrow) accompanied by a rib fracture (purple arrow).

In medicine, a disease is considered asymptomatic if a patient is a carrier for a disease or infection but experiences no symptoms. A condition might be asymptomatic if it fails to show the noticeable symptoms with which it is usually associated. Asymptomatic infections are also called subclinical infections. Other diseases (such as mental illnesses) might be considered subclinical if they present some but not all of the symptoms required for a clinical diagnosis. The term clinically silent is also used.

Knowing that a condition is asymptomatic is important because:

An example of an asymptomatic disease is Cytomegalovirus (CMV) which is a member of the herpes virus. "It is estimated that 1% of all newborns are infected with CMV, but the majority of infections are asymptomatic." (Knox, 1983; Kumar et al. 1984) In some diseases, the proportion of asymptomatic cases can be important. For example, in multiple sclerosis it is estimated that around 25% of the cases are asymptomatic, being these cases detected postmortem or just by coincidence (as incidental findings) while treating other diseases.

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