Virus
Viruses are the smallest agents of infectious disease. Most viruses are exceedingly small (about 20 - 200 nanometers in diameter) and essentially round in shape. They consist of little more than a small piece of genetic material surrounded by a thin protein coating. Some viruses are also surrounded by a thin, fatty envelope. Viruses are different from all other infectious microorganisms because they are the only group of microorganisms that cannot replicate outside of a host cell. Because viruses do not eat food - instead they seize materials and energy from host cells by hijacking cellular machinery - some scientists argue that they are more like complex molecules than living creatures. Viruses are known to infect nearly every type of organism on Earth. Some viruses, called bacteriophages, even infect bacteria.
Bacteria
Bacteria are ten to 100 times larger than viruses. They are typically 1 to 3 microns in length and take the shape of a sphere or rod. Most bacteria consist of a ring of DNA surrounded by cellular machinery, all contained within a fatty membrane.They acquire energy from the same essential sources as humans, including sugars, proteins, and fats. Some bacteria live and multiply in the environment while others are adapted to life within human or animal hosts. Some bacteria can double in number every fifteen minutes while others take weeks or months to multiply. Bacteria cause many types of diseases, ranging from mild skin irritation to lethal pneumonia.
Parasites
Parasites are part of a large group of organisms called eukaryotes. Parasites are different from bacteria or viruses because their cells share many features with human cells including a defined nucleus. Parasites are usually larger than bacteria, although some environmentally resistant forms are nearly as small. Some parasites only replicate within a host organism, but some can multiply freely in the environment. Parasites can be made of one cell, as in the case of Giardia, or many cells, as with parasitic worms
"Parasite" has multiple meanings. Most broadly, a parasite is anything that lives off and benefits from another being. By that definition viruses
are parasites, and that's a pretty common use of the term. Many definitions of virus include the point that they're parasitic.
Another definition of parasite is much more narrow; it includes infectious organisms that are not viruses and bacteria. That includes such things as protozoa (like malaria, giardia, trypanosomes, and many more), various kinds of worms (hookworms, guinea worms, tapeworms, etc etc), and things like lice and so on. By that definition viruses are not parasites because they're simply defined as not being part of that group.
But it's just a definition, which means that so long as you agree on what you mean, you can call a virus anything you like.
In American politic view: China created the virus; In China politic view: U.S created the virus; In Scientific view: there are not enough evident the virus was created in Wuhan China.
I am an American not Chinese. See my flag.
