Is a virus a poison?

Virus is more complicated than just a protein. Rather it is a collection of proteins and nucleic acids (the viral genome), packaged in a certain way. When virus penetrates a cell, it hijacks the cellular machinery, making the cell produce many copies of the initial virus.

Unlike a cell, virus does not have all the necessary elements for reproduction, i.e. for copying its genome, generating all the necessary proteins, and ingesting food for powering this reproduction activity. This is why one says that viruses are not alive, whereas cells are alive. A cell can exist and reproduce without virus, but not vice versa.

A poison can a simply a small molecule (not necessarily an organic one) which is capable of disrupting normal functioning of a cell, e.g., by binding to some of its proteins.

Although "Virus" literally means "Poison" in Latin, it would be a great over-simplification to regard a Virus as a Poison.

Now, most poisons are chemical compounds that interfere in some chemical pathway in our body. For example:

1. Carbon Monoxide: Binds with Haemoglobin, rendering it unable to transport oxygen
2. Sarin: Indirectly inhibits degradation of the neurotransmitter "Acetylcholine" at the synaptic cleft. Mechanism of action of Sarin

Hence most poisons are quite "simple" in their actions. However, viruses can be considered as a complex machinery of functions that interfere with a multitude of processes in our body including cell transcription, receptor-mediated endocytosis, et.c

Hence, the best analogy would be to consider a virus as a tactical poison.

Now, as for last question, viruses are fragile assembled structures. Viral Self-Assembly

Environmental factors like heat, uv-light, oxygen, etc may damage the assembled structure. Hence, viruses have a self life, and so do may poisons. Sarin (self life)

However, poisons tend to have a longer self life because chemical compounds are more stable than the capsid of viral proteins with weak hydrogen bonds.

As per David 's suggestion, poison is defined as "...substances that cause death, injury or harm to organs, usually by chemical reactions or other activity on the molecular scales, when an organism is exposed to a sufficient quantity." Wikipedia

Viruses do work at molecular level, but not in the same sense as poisons do. Hence, viruses do fit into the description of poisons but not precisely.

Hope you find this helpful.

Is a virus a poison?

In toxicology, a virus is not classified as a toxic agent or a poison but as a biological agent (regardless of whether you consider it to be living or not). With the main distinction being the biological agents reproduce. You can find different definitions of "poison" in different sub disciplines of toxicology, but generally it's any substance capable of causing toxic effects in relatively small quantities. A "substance" in this case is considered to be a single agent. Just as salt-water is not a single substance but a mixture of substances, a virus is a structured organism made of proteins, nucleic acids, and other macro-molecules. Its often the case that none of these different parts are solely responsible for the toxic effects of a virus, but instead it's the action of viral replication which causes cellular damage leading to disease.

There are some biological agents which also produce toxins or poisons. One example is Clostridium tetani. This organism can infect an open wound, but it's toxicological effects are not a result of direct tissue damage caused by the organism, but of the tetanospasmin toxin it produces, which is a potent neurotoxin and the causative agent of tetanus. Again, in this case, C. tetani is the biological agent, but tetanospasmin is the toxin/poison.

we all know by now that viruses can only remain harmful/intact on surfaces for a certain amount of time. However, I would think that a poison on a surface does not have such a time limit

Neither statement is universally true. There are viruses that can remain infectious for months in the environment, and some bacterial spores that can survive for years. There are also some insecticides (poisons for insects) that breakdown in a matter of days in the environment. It just depends on the specific properties of each different agent, and on the environment they are in.