What's the difference between a bacteria and a virus?

Both bacteria and viruses are so small that they can only be seen through a microscope, and both have the ability to cause infection, but that’s where the similarities end.

Bacteria

Bacteria are one-celled organisms that can be found naturally throughout our bodies and in our environment. Most are harmless and do not cause infection. Bacteria in our bodies help us to digest food, protect us against other bacteria or microbes, and provide nutrients for our body. Seen under a microscope they look like rods, balls, or spirals, and they can multiply quickly under the right conditions. Less than one per cent of bacteria actually make us sick. Infections caused by bacteria include strep throat, tuberculosis, and urinary tract infections (UTI).

Antibiotics are available to treat most bacterial infections; however, it is often best to let your body’s own immune system fight them if it is able to.

Viruses

Viruses on the other hand, cannot live without a host, or another living creature to help them multiply. Viruses are smaller than bacteria and they attach themselves to another living cell and use that cells' genetic material to reproduce themselves. Most viruses cause disease. Examples of diseases caused by viruses include the common cold, herpes, shingles, measles, chickenpox, COVID-19 and AIDS.

Antibiotics will not treat a viral infection. Viral infections require either vaccinations to prevent them in the first place or antiviral drugs to inhibit their development.

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. They can only reproduce by attaching themselves to cells. In most cases, they reprogram the cells to make new viruses until the cells burst and die. In other cases, they turn normal cells into malignant or cancerous cells.

Also unlike bacteria, most viruses do cause disease, and they're quite specific about the cells they attack. For example, certain viruses attack cells in the liver, respiratory system, or blood. In some cases, viruses target bacteria.