Final answer:
Diseases can be carried by individuals who are infected but not showing symptoms. These individuals, known as active carriers, can transmit the pathogen to others.
Step-by-step explanation:
Diseases are often caused by pathogens, which are infectious agents that can cause harm to their hosts. In the case of human diseases, the carriers of these pathogens can be people who are infected but not showing symptoms. These individuals are known as active carriers and can transmit the pathogen to others. The carriers of diseases can be anyone, regardless of whether they have symptoms or not.