What are viruses and how do …

Viruses are tinier than bacteria. In fact, the largest virus is smaller than the smallest bacterium. All viruses have is a protein coat and a core of genetic material, either RNA or DNA. Unlike bacteria, viruses can't survive without a host.

Bacteria are simple, single celled organisms, called prokaryotes, which means their DNA is contained within a certain area of the cell called the nucleoid, but not enclosed. Bacteria are one of the oldest living things on earth, having been in existence for at least 3.5 billion years. A microscope is needed to see them.

• Bacteria and viruses differ in their structure and their response to medications.
• Bacteria are single-celled, living organisms. They have a cell wall and all the components necessary to survive and reproduce, although some may derive energy from other sources.
• Viruses are not considered to be “living” because they require a host cell to survive long-term, for energy, and to reproduce. Viruses consist of only one piece of genetic material and a protein shell called a capsid. They survive and reproduce by “hijacking” a host cell, and using its ribosomes to make new viral proteins.
• Less than 1% of bacteria cause disease. Most are beneficial for our good health and the health of Earth’s ecosystems. Most viruses cause disease.
• Antibiotics may be used to treat some bacterial infections, but they do not work against viruses. Some severe bacterial infections may be prevented by vaccination.
• Vaccination is the primary way to prevent viral infections; however, antivirals have been engineered that can treat some viral infections, such as Hepatitis C or HIV. Antivirals are not effective against bacteria.