Elder berries are almost a household word when it comes to herbal antivirals. Covid rocketed it to fame, and the science behind it is strong. https://www.tandfonline.com/doi/full/10.1080/09540105.2021.1978941
Water-soluble compounds in elder berries prevent and deal with corona viruses. Elder grows easily. The birds eat all my berries though, so i buy dried ones. Using one ounce or more of the dried berries, I make a quart of infusion, which I double-decoct down to a cup of liquid. I add a little less than one cup of honey (or sugar) to this and bring back to boiling. I bottle it boiling hot in well-washed jars and lid well. After it cools, it lives in the refrigerator.
Two cups of elder berry syrup to sip all winter. Smile.

Sauerkraut has strong anecdotal evidence as well as some solid science. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8036130/
You can make your own. Or buy it from someone who has made it. Heated/pasteurized sauerkraut is not antiviral. It's fun and easy to make sauerkraut. All you need is a jar, salt, and some muscle.
Layer shredded fresh cabbage in a jar with salt. Press down hard. Harder. Really hard. Repeat. Press. I aim to get an entire head of cabbage in one quart jar. Pressing causes liquid to be released. Press until there is enough liquid to entirely cover the cabbage. Lid and let sit at room temperature for five or more days. Then refrigerate.
I eat (at least) a tablespoonful of sauerkraut daily preventatively.

It's too late this year to provide yourself with two other antiviral herbs — St. Joan's wort and shiso — but you can plan to plant them both next year.
Shiso self-seeds readily. I prefer the flat-leaf purple variety for medicine.
Only Hypericum perforatum is medicinal, no other species.
And then there is licorice.

Hypericum — St. John's/Joan's wort — is the unsung herbal antiviral. It resists being an item of commerce; demanding to be harvested flower by flower, day by day, by hand to preserve her power. Perfect for people's medicine; rotten for corporate greed.
Tincture of the fresh flowers has, in my experience, successfully countered a wide range of viral infections, from herpes to corona viruses. Science agrees. https://www.news-medical.net/news/20220427/St-Johns-wort-extract-shows-potent-antiviral-activity-against-SARS-CoV-2-and-its-variants.aspx
You'll learn lots more at our virtual Hypericum Conference in 2023.

Shiso (Perilla frutescens) "significantly decreased virus-induced cytokine release and viral protein/RNA levels in human lung epithelial cells. . . " The extract "is capable of inhibiting SARS-CoV-2 replication by inactivating the virion."
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7840404/

Licorice — the herb, not the candy, which is usually flavored with anise oil — has proven itself to be one of the very best anti-virals. But I rarely use it.
It is easy to buy, and tasty, but not easy to grow. And it contains a compound (glycyrrhizic acid ) that can raise blood pressure. It is safest to use licorice that has this substance removed — called deglycyrrhizinated licorice (DGL). That means, even if i could grow it, I would still need to purchase it to use as an antiviral. No thanks.
Stephen Buhner is very found of licorice as an antiviral. He tells us about it — with explicit instrucions for use and doses — in his wonderful book Herbal Antivirals, available at wisewomanbookshop.com

Now that we are prepared to deal with colds and flus with anti-infective and anti-viral herbs, let's do more to prevent them. Part 3 will offer us some antioxidant-rich ideas.
Green blessings to you all.

Part 3 .. >>