Viruses are small obligate intracellular parasites, which by definition contain either a RNA or DNA genome surrounded by a protective, virus-coded protein coat. Viruses may be viewed as mobile genetic elements, most probably of cellular origin and characterized by a long co-evolution of virus and host.

Parasites as vectors affecting the transmission of viruses. In some cases, the virus-infected parasite might facilitate the transfer of the virus to the human host. Parasites harboring viruses with unidentified effects on their host.

Viruses are small obligate intracellular parasites, which by definition contain either a RNA or DNA genome surrounded by a protective, virus-coded protein coat. Viruses may be viewed as mobile genetic elements, most probably of cellular origin and characterized by a long co-evolution of virus and host.

Viruses have been termed the ultimate parasite. To replicate, viruses must release their genome composed of either DNA or RNA (either single- or double-stranded, or in rare cases both), inside a cellular host. This release process, or infection, occurs by disassembly of the extracellular virus particle, the virion.

Bacteria and viruses can live outside of the human body (such as on a countertop) sometimes for many hours or days. But parasites need a living host to survive. Bacteria and parasites can often be killed with antibiotics. But these medicines can't kill viruses.

FALSE. Many infectious diseases are caused by viruses and bacteria. But there are also other types of pathogens that cause illness.

False. While many viruses do cause diseases and are considered parasites, not all viruses cause diseases. Some viruses can exist in a host without causing any harm or symptoms, and there are even some beneficial viruses that help their host organisms.