Answer: in many different ways.
With soap and water: dissolve its coat and expose the nucleic acid. RNA will break down quickly. DNA is a lot more resistant. You can get a similar result with alcohol (higher than 60% and a bit less reliable).
Time: RNA will decay.
Essential oils: these work in many different ways because essential oils are made of many different chemicals so the answer will depend on the chemical/s.
Remember selectivity: you don’t want to kill your own cells while destroying viral particles! Essential oils are concentrated chemical solutions, you can dissolve plastic with some of them!
How do plant chemicals stop a virus? Here are some examples.
Lectins: interact with viral membranes. Canavalia ensiformis, Lens culinaris, Phaseolus vulgaris, Triticum vulgaris. But reember that lectins can also be very toxic. It is not you who shuld be looking for a good lectin!
Polysaccharides block virus binding. And here you can use Achyrocline flaccida, Bostrychia montagnei, Cedrela tubiflora, Prunella vulgaris, Sclerotium glucanicum, Stevia rebaudiana, Rhizophora mucronata. Or, much simpler, try sea kelp bioferment and fucoidans in Skin Actives Scientific products.
Flavonoids can interfere with the synthesis of viral RNA. Examples are amentoflavone, theaflavin, iridoids, phenylpropanoid glycosides, agathisflavone, robustaflavone, rhusflavanone, succedaneflavanone, chrysosplenol C, morin, coumarins, galangin (3,5,7‐trihydroxyflavone), baicalin
Terpenoids like sesquiterpene, triterpenoids (moronic acid, ursolic acid, maslinic acid and saponin) inhibit viral DNA synthesis and interact with membranes.
Lignans can block viral replication.
Miscellaneous phenolic compounds can block RNA and DNA viral replication and include anthraquinone chrysophanic acid, caffeic acid, eugeniin, hypericin, tannins (condensed polymers), proanthocyanidins, salicylates and quinines (naphthoquinones, naphthoquinones and anthraquinones in particular aloe emodin).
Some plant proteins and peptides interact with ribosome function in the infected cell and inhibit viral protein synthesis or inhibit reverse transcriptase.
Where do we go from here?
It is true that it is possible to use some of these plant chemicals to beat a virus (plants beat there own viruses this way) but it is so important not to hurt the patient as it is to destroy the virus so quite often scientists have to modify the original plant chemical in order to make it into an effective tool.
In the meantime, see what Skin Actives is doing with essential oils in Part B of this article.