Final answer:
Viruses can be both harmful and beneficial to humans; they cause diseases but also are used in medical research, gene therapy, and the creation of vaccines.
Step-by-step explanation:
It is true that viruses can be both harmful and beneficial to humans. While many viruses cause diseases in humans ranging from the common cold to more severe diseases like Ebola and COVID-19, viruses also have applications in medicine and research. They have been utilized in genetic engineering as tools to insert DNA into host cells, in the development of vaccines to stimulate protective immunity, and in the production of antiviral drugs. Moreover, some viruses are being researched for their potential use in targeting and killing cancer cells, as well as treating genetic disorders. It's important to recognize that not all viruses cause disease, and their role in medicine and research is indispensable.