Viruses
Non-living particlesSmallest pathogen; much smaller than a bacteria cellCan only reproduce inside a living cellNot killed by antibioticsDisease examples: influenza, measles, chicken pox, HIV, and coronavirus
Viruses are infectious agents that can replicate within living cells. They are not considered living organisms because they cannot carry out their own metabolic functions, but instead rely on a host cell to reproduce and spread.
Viruses typically have a protein coat (called the capsid) surrounding genetic material (such as DNA or RNA). Some viruses also have an outer envelope made up of lipids.
Viruses can infect all forms of life, including humans, animals, plants, and bacteria. They can cause a range of illnesses, from common colds and flu-like symptoms to more severe diseases such as AIDS, Ebola, and COVID-19.
There are several ways in which viruses can be transmitted, including through direct contact with bodily fluids (e.g. blood, saliva), through inhaling airborne particles or respiratory droplets, or by coming into contact with contaminated surfaces or objects.
Preventative measures for viral infections include regular hand washing, avoiding close contact with sick individuals, practicing good respiratory hygiene (e.g. coughing/sneezing into a tissue or elbow), and vaccination when available. Treatment options for viral infections vary depending on the specific virus and can include antiviral medications, symptom management, and rest.
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