Bacteria and viruses often are mixed with each other, but they are very different. The bacteria are generally harmless and viruses are usually harmful, although there are bad bacteria and useful viruses.
Viruses are simpler than bacteria, consisting of the genetic code (DNA or RNA) with protein shell – some scientists describe them as alive. Viruses are from 20 to 250 nanometres.
Some viruses can be useful – viruses called bacteriophages ( refers to “bacteria eater”) kill bacteria and are used to protect people from harmful bacteria in food.
Most viruses cause diseases – from colds and flu are caused by viruses, and common illnesses such as chicken pox, measles, mumps and rubella (German measles). HIV, which causes AIDS, is a virus.
There is no vaccine against colds, as there are so many different viruses that cause colds.
The viruses are transmitted by sneezing and coughing or by touching someone who has a viral infection – it is important to cough or sneeze into a tissue and wash your hands regularly when infected with a cold or other viral infection.
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