Solutions for:. Unlike the in-depth articles in the Knowledge Base, every definition in the Glossary is succinct, while remaining highly informative. This section is currently under construction. In the Knowledge Base, you will find various articles about common threats, a general classification of malware and unwanted messages, and a brief historical overview of the evolution of these and many other threats. The Knowledge Base now has three main sections: — The Detectable Objects section gives detailed information about malicious and potentially dangerous programs that we protect users against every single day all around the world, as well as advice on what to do in case of infection.
Strictly speaking, however, a virus is defined as program code that replicates. Of course, this simple definition leaves plenty of scope for further sub-division. However, some viruses are not successfully treated by the immune system, such as human immunodeficiency virus, or HIV.
This leads to a more chronic infection that is difficult or impossible to cure; often only the symptoms can be treated. Unlike bacterial infections, antibiotics are ineffective at treating viral infections. Viral infections are best prevented by vaccines, though antiviral drugs can treat some viral infections. Most antiviral drugs work by interfering with viral replication. Some of these drugs stop DNA synthesis, preventing the virus from replicating. Although viruses can have devastating health consequences, they also have important technological applications.
Viruses are particularly vital to gene therapy. Because some viruses incorporate their DNA into host DNA, they can be genetically modified to carry genes that would benefit the host. Some viruses can even be engineered to reproduce in cancer cells and trigger the immune system to kill those harmful cells. Although this is still an emerging field of research, it gives viruses the potential to one day do more good than harm.
Antibiotics do not stop viruses. Also called the flu. The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. The Rights Holder for media is the person or group credited. Tyson Brown, National Geographic Society. National Geographic Society.
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You cannot download interactives. People get sick when another organism, big or small, invades their body and infects them. These infectious agents come in all shapes and sizes, and all of them pose different threats to the human body. Some are microscopic, such as bacteria or viruses, which attack human bodies on the cellular level. Others are larger, like fungi, which are unicellular or multicellular organisms that grow on and feed off organic material, including humans.
Finally, parasites such as tapeworms can find their way inside the human body and feed on blood and nutrients without killing their host. Learn more about infectious agents and their impact on human health with this curated resource collection. Even the most basic parts of a cell can enable complex cellular processes, and multifunctional organelles expand these capabilities to make advanced activities possible for higher life-forms. Organelles are specialized structures that perform various tasks inside cells.
Join our community of educators and receive the latest information on National Geographic's resources for you and your students. Skip to content. Image virus Viruses are microscopic biological agents that invade living hosts and infect their bodies by reproducing within their cell tissue.
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