Bacteria, fungus, and viruses are not removed by Brita filters. When we assume our water has been "purified," it has most likely been scrubbed of chlorine, as we just discovered. Most people, however, believe that they will receive pure, flavorless water. This is not true; instead, they are receiving water that has had many chemicals removed from it. For example, fluoride is used to prevent tooth decay; however, it can also be harmful if not removed. Viruses are microscopic particles that can cause illness when consumed. Some viruses may infect bacteria that are able to reproduce inside our cells. These bacteria then create more viruses which could eventually lead to death of the host cell. Humans are only susceptible to a few viruses known as "enveloped" viruses because they need living cells to reproduce. Other viruses are "non-enveloped" and can reproduce using synthetic materials instead. There are several methods used to reduce the number of viruses in drinking water including pre-treatment with carbon or other filters, direct filtration, treatment with chlorine, and treatment with ultraviolet light. Chlorine kills both bacteria and viruses. It does this by forming a protective layer on the inside of the glass of the bottle that prevents any additional organisms from entering your bottle of water. The amount of chlorine required to disinfect your water varies depending on the type of contaminant you want to remove. For example, to remove bacteria you need about 0.