So first of all it might be well to describe what's going on right after your guests have checked in.
 They have entered through your nose or mouth (perhaps even the eyes, according to some experts). Here is a description of a typical coronavirus attack, by Dr. Martin S. Hirch, senior physician in the Infectious Diseases Services at Massachusetts General Hospital:

"Once inside, the virus begins infecting epithelial cells in the lining of the lung. A protein on the receptors of the virus can attach to a host cell's receptors and penetrate the cell." [My note: that's the little cone-shaped spikes you see in photographs of Coronaviruses.]
 "Once inside the host cell, the virus begins to replicate until it kills the cell. This first takes place in the upper respiratory tract, which includes the nose, mouth, larynx and bronchi. The patient begins to experience mild versions of symptoms: dry cough, shortness of breath, fever and headache and muscle pain and tiredness, comparable to the flu."

This is your chance to mount your defense!
 As Dr Hirch describes it: "Symptoms become more severe once the infection starts making its way to the lower respiratory tract." So you want to try to do something before this happens.
 "But what can I do?" you ask. There's no vaccine for the current Coronavirus, and flu shots only work for certain selected flu viruses, and we've all been told that there's nothing you can do about colds. And I'm sure that all of you know that antibiotics don't work against viruses, though they may help against secondary bacterial infections like strep throat.
 On the other hand, Medical Science offers several anti-viral compounds, most of which require a prescription. That alone would seem to be a big show-stopper: You would have to set up an appointment with a health care provider - and they're all overloaded beyond capacity. Then comes the Waiting Room Gauntlet where you are surrounded by bug-eyed folks who are all well past the incubation stage. Then you have to go to the Pharmacy Gauntlet, surrounded by more of the same folks. But you will have lost valueable time and your Early Mover advantage.
 Of note is that there may be online services that can connect you to a doctor or nurse who might be able to give you the prescription. That only leaves you with the Pharmacy Gauntlet.
 One of Medical Science's anti-virals is the well-known Tamiflu. In light of what I am about to discuss below, it is of interest to note that Tamiflu was once derived from Shikimic Acid in the Star Anise flower, and has been manufactured for many years using this natural component, although it is now usually synthesized using fermented, genetically-modified E. Coli bacteria. (Another method involves extracting Shikimic Acid from Ginko Biloba trees.)
 Tamiflu is currently by prescription only but may soon be able to be purchased "Over the Counter". It is generally not suggested unless you have underlying conditions, or perhaps live in a nursing home. Further, it has never been tested as being effective against SARS-CoV2. Also, you can't just go get a prescription "just in case".

So, what about herbals? Might there be another compound in nature that offers anti-viral activity like the Shikimic Acid in the Star Anise Flower and the Ginko Biloba tree? It does turn out that there is an herbal anti-viral compound that is safe, readily available, and can be taken any time you want to be proactive against a possible viral infection. (It has never been tested as being effective against SARS-CoV2, however). Actually, it may or may not be "readily available" right now, since the secret's out and has been out for quite some time (over 2,000 years, actually). So you might have to shop around.
 This compound is Elderberry.
 I first learned about the effects of Elderberry several years ago, when I was doing research on herbal remedies for colds and flu - after two Christmases in a row where most of us caught colds during/after family reunions. Since then I have consistently found that if I took some Elderberry Zinc lozenges at the first sign of colds - sore throat, runny nose and sneezes - the cold never happened, or was very mild. My wife and kids report for the most part similiar outcomes. During that research I learned the reasons for Elderberry's unusual effectiveness. I will present these characteristics.

First of all, one thing about cold temperatures and virual infection. We find ourselves asking "Why are colds and the flu more prevalent during the colder seasons?" One obvious reason is that everybody is cooped up indoors more during the winter. But the other relates to humidity and dryness rather than cold! Lower humidity dries up our mucus membranes, so that the cilia are no longer able to sweep viruses out of the respiratory mucosa! Sometimes the mucus membranes become so dry they begin to develop cracks, allowing viral entry.
 And second of all, may I offer a quote about our current disconnect from remedies that have been handed down for many years and from many cultures:

"Over years of teaching herbal medicine, I have found that many people are at a loss as to how to tend to illnesses such as a cough, cold, or flu. Yet, from such diverse ancient cultures as Egypt, Europe, Greese, Persia, India, and China, effective home remedies were passed on from one generation to the next. But for the modern person, much of this knowledge has been lost. Learning some of these ancient remedies can help dispel the feelings of helplessness and make an ailing person feel more comfortable."
 Ref: Candis Cantin Kiriajes, in Herbal Remedies 2017, Harris Publishing

The first, and most convincing, fact about Elderberries and their activity came from one of the many herbal books/magazines that I purchased. The author of that book clearly knew her field well, and provided the technical nutritional information supporting the various claims made for each of the herbs that were presented and discussed in the book. For Elderberries:

"Elderberry juice and syrup have been use for more than 2,000 years in the treatment of colds, flu, and coughs. . . The flavonoids in the berry help bind and disarm hemagglutinins, tiny viral spikes covered with the enzyme neuraminidase, which allows the virus to penetrate cellular membranes."
 Ref: The Desktop Guide to Herbal Medicine, Brigitte Mars A.H.C., Basic Health Publications, 2007.

Back then, I knew nothing about "Neuraminidase" or "Hemagglutinins". Today, during the pandemic, these two terms are in just about every other article about SARS - CoV2! They are the "N" and "H" in discussions about viruses, E.G.: H1N1 (SARS), H5N1 (Avian flu).
 Nonetheless, that sounded technical enough for me at the time to pursue other research on Elderberry.
 Of note, here's a quote regarding Tamiflu:

Tamiflu works by inhibiting the enzyme (viral neuraminidase) which promotes the spread of a virus in the respiratory tract.

Ref: Sharon Orrange, MD, at Goodrx.com

https://www.goodrx.com/blog/ten-things. . .

More references concerning Elderberry:
First up is an article in 2004, discussing the benefits of a particular Elderberry compound, Sambucol. Apparently a Dr. Madeleine Mumcuoglu founded a company named Razei Bar in Israel to manufacture an Elderberry compound that she named Sambucol. She said, "I became interested in the natural healing elements of elderberry when I did by PHD on it in Switzerland."
 She conducted a study on actual patients during a flu epidemic in southern Israel in winter 1992 - 1993. The results:

"Within 24 hours, 20% of those patients taking Sambucol had dramatic improvements in symptoms like fever, muscle aches and pains and coughing. By the second day, 73% were improved and by day three, 90%. In the untreated group, only 16% felt better after two days. The majority of the control group took almost a week to begin feeling better.
 Another double-blind placebo-controlled clinical study was conducted using Sambucol during an outbreak of influenza B Panama. A significant improvement of the symptoms, including fever, was seen in 93.3% of the cases in the Sambucol treated group within 2 days. A complete cure was achieved within 2 to 3 days in nearly 90% of the Sambucol treated group and within at least 6 days in the placebo group." [My notes: influenza B is considered weaker than influenza A. Hence the rather short recovery times.]

The site from which the above quotes originated also listed another randomized, double-blind, placebo-controlled study in Norway. The study concluded that Sambucol was shown to "significantly reduce the duration of the flu by approximately four days."

[It should be noted that these are not necessarily unbiased studies. They may have been funded at least in part by the Dr Mumcuoglu or by her company.].

Ref: "Israel's elderberry remedy Sambucol provides solution to U.S. flu vaccine shortage", David Brinn, Oct 31, 2004

israel21c.org/israels-elderberry-remedy-sambucol. . .

In 2019, the University of Sydney conducted a study on the use of Elderberry to minimize flu symptoms. This study was carried out by the University of Sydney's Faculty of Engineering and IT.

"The study was conducted by Professor Fariba Deghani, Dr Golnoosh Torabian and Dr Peter Valtchev as part of the ARC Training Centre for the Australian Food Processing Industry that was established in the Faculty of Engineering and IT.
 The purpose fo the study was to perform a comprehensive examination of the exact mechanism by which phytochemicals from elderberries combat influenza infections. The researchers used commercially farmed elderberries which were reduced into a juice serum and were applied to cells before, during and after they had been infected with the influenza virus.

Dr Torabian is quoted as saying, "What our study has shown is that the common elderberry has a potent direct antiviral effect against the flu virus. . . It inhibits the early stages of an infection by blocking key viral proteins responsible for both the viral attachment and entry into the host cells."
 The researchers found that the phytochemicals from the elderberry juice were "effective at stopping the virus from infecting the cells. But they were surprised to find that the phytochemicals "were even more effective at inhibiting viral propagation at later stages of the influenza cycle when the cells had already been infected with the virus."
 Dr Valtchev noted: "This observation was quite surprising and rather significant because blocking the viral cycle at several stages has a higher chance of inhibiting the viral infection."

[It should be noted that this was an "in vitrio" type study. That is, the Eldeberry compound was applied to viruses in the lab, not in human subjects. In vitrio research is often the predecessor to human studies. Unfortunately, the big grant bucks for human studies always go to the larger Pharmaceutical companies. They can afford to fund research because they stand to make millions on a successful drug. That's why you don't see many studies on natural compounds.]

Ref: Elderberry compounds could help minimize flu symptoms, study suggests, University of Sydney, 4/23/2019

sciencedaily.com/releases/2019/04/190423133644.htm

Another site (healthline.com) provides a summary of the other health benefits of Elderberries:

High in vitamin C (6-35 mg of C per 100G)

High in fiber (7 G per 100G)

Good source of phenolic acids (antioxidants)

Good source of flavonols, including quercetin, which is associated with modulating histamine response

rich in anthocyanins. These impart the dark purple/black color.

The site then cites three additional studies showing anti-viral effects. Two are described here:

"One study of 60 people with influenza found that those who took 15 ml of elderberry syrup four times per day showed symptom improvement in two to four days, while the control group took seven to eight days to improve." (cited from https://pubmed.ncbi.nlm.nih.gov/15080016/).
 "Furthermore, a study of 312 air travelers taking capsules containing 300 mg of Elderberry extract (Rubini, BerryPharma AG) three times per day found that those who got sick experienced a shorter duration of illness and less severe symptoms." (cited from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4848651/. This is the "very long" version. A summary, or "Abstract" is available from https://www.ncbi.nlm.nih.gov/pubmed/27023596).

[It should be noted that the air traveler study was funded in part by the Iprona company, whose extract division is BerryPharma AG]

Ref: Elderberry: Benefits and Dangers

https://www.healthline.com/nutrition/elderberry. . .

You've probably had enough of references, but I wish to cite one more, because of the particular type of Elderberry compound used in the study. This one is from the US National Library of Medicine/National Institutes of Health site. It is very technical, so I will provide the summaries only.

"Background:
 Black elderberries (Sambucus nigra L.) are well known as supportive agents against common cold and influenza. It is further known that bacterial super-infection during an influenza virus (IV) infection can lead to severe pneumonia. We have analyzed a standardized elderberry extract (Rubini, BerryPharma AG) for its antimicrobial and antiviral activity using the microtitre broth micro-dilution assay against three Gram-positive bacteria and one Gram-negative bacteria responsible for infections of the upper respiratory tract, as well as cell culture experiments for two different strains of influenza virus.
 Results:
 For the first time, it was shown that a standardized elderberry liquid extract possesses antimicrobial activity against both Gram-positive bacteria of Streptococcus pyogenes and group C and G Streptococci, and the Gram-negative bacterium Branhamella catarrhalis in liquid cultures. The liquid extract also displays an inhibitory effect on the propagation of human pathogenic influenza viruses.
 Conclusion:
 Rubini elderberry liquid extract is active against human pathogenic bacteria as well as influenza viruses. The activities shown suggest that additional and alternative approaches to combat infections might be provided by this natural product.

[It should be noted that this was also an "in vitrio" type study. That is, the Eldeberry compound was applied to viruses in the lab, not in human subjects].

Ref:Inhibitory activity of a standardized elderberry liquid extract against clinically-relevant
human respiratory bacterial pathogens and influenza A and B viruses

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3056848/

NOTE: It needs to be firmly stated that no study has yet been conducted on Elderberry (and possibly even Tamiflu) in regard to SARS-Cov2. Elderberry has a long history of use by many cultures as being helpful against respiratory infections, and it has intriguing success in some smaller studies in modern times as being useful against certain influenza viruses, though again this does not include SARS-CoV2. This article is not intended to taken as promoting a cure, or even a certain preventative, against the current viral pandemic.

Nonetheless, it would seem that using Elderberry is better than helplessly standing by and serving as a "virus motel"! You can even combine Tamiflu's (former) active ingredient with Elderberry! Searching the internet will yield several recipes for Elderberry/Star-Anise syrups and teas.

A note about specific Elderberry compounds:
 Prior to doing research on this article, I wasn't too particular on what kind of Elderberry product I employed. As a matter of fact, I have been using Zand's Elderberry Zinc Lozenges. They are supplied in small plastic bags of 15 lozenges.
 The studies above were carried out using various Elderberry preparations (highlighted in red in the above paragraphs). Some of the preparations are unspecified ("Eldeberry syrup" and "Elderberry Extract"). But two specific products are shown - Sambucol and Rubini (BerryPharma).
 You have likely heard that one problem with herbal compounds is the wide variation in the concentration of the active phytonutrients. So there might be an advantage in choosing something that was actually used in a scientific study; you would then know that whatever the product's formula is, it in fact was shown to work on bacteria and certain viruses, at least in certain specific Trials. With that in mind, here are the two products.

One is Sambucol.
 Sambucol is apparently the direct descendent of the product originally created by Israeli researcher Dr Mumcuoglu and her company, Razei Bar in Israel. The 2004 article cited above notes that Sambucol was subsequentially offered in the U.S. by Nature's Way. However since then, due to licencing or other problems, Nature's Way no longer sells a product named "Sambucol"; their other products may or may not be descendents of the original Israeli product. Sambucol itself is now distributed by PharmaCare, based in Europe. Additionally, Sambucol is said to be produced from "Haschberg" variety of elderberries in central Europe, which are claimed to have twice the anthocyan content of wild elderberries
  You can decide for yourself about the uniqueness of Sambucol, but it apparently does have the distinction of being related to Dr Mumcuoglu's original research, and its predecessor was used in several studies and found to be effective against various viruses. For example, a 2006 article from israel21c.org notes that Sambucol was effective in vitrio against H5N1 Avian flu viruses. Sambucol has its own website: "SambucolUSA.com", and Sambucol is available on Amazon.

The other is Rubini.
 I had trouble finding any references to "Rubini", other than it is associated with an Italian company called "Iprona". I contacted them and received a reply (which surprised me, since Italy has been having such a problem with SARS-CoV2!!).
 It turns out that "Rubini" is the former name of their Elderberry Extract. In early 2018, the company re-branded the name to "Eldercraft". In the words of their rep:
 "The name stands for a premium extract, which is made from selected European black elderberry fruits. Iprona has contracted farmers in Austria which exclusively produce Elderberry raw material fruits for the extract. Additionally, the extract is a 'water extract', meaning that it is not made by extraction with solvents like ethanol or methanol but with water only." Further, the Iprona-supplied extracts are said to be produced from a particular European variety of Elderberries - called "Haschberg".
 It turns out that Iprona is a supplier of raw materials (extracts) to other companies. They do not have a product available for sale to the public.
 For specific products that contain the "Eldercraft" processed Elderberries, it takes some diligent searching. A search for "Eldercraft" Elderberries on Amazon does yield various products whose description indicates that the product is made using the Haschberg Elderberries and has a non-solvent type of extraction. One is "Eldercraft" by "B.B. and G. Health Corp" from Canada. Another is Sambu-C, which also contains Vit. C and Acerola Berry. Another is allKidz Anti-Cold for kids. These three products reference the "Eldercraft" extraction method, as well as Iprona on their packages. And finally there is "Naturade Standardized Elderberry Extract" syrup, which also contains buckwheat honey. This product references the "Eldercraft" extraction method but not Iprona specifically.
 Another online source is dyna-nutrition: (dyna-nutrition.com/products/black-elderberry-juice/). It references Eldercraft/Iprona as well.
I have contacted most of these suppliers for more information, and will update this article when I hear from them.

For the present, I'm sticking with my Zand's Elderberry Lozenges, although I might note that they are not "standardized" in any way. But I did purchase a couple of bottles of one of the Eldercraft products.

A final note: Some of the studies mention that Elderberry stimulates the production of inflammatory cytokines (immune system mediators). For most people this is considered a healthy immune response. However there are reports of an excessive cytokine production in people who have advanced SARS-CoV2 infections - the "cytokine storm", usually associated with "ARDS" (Acute Respiratory Distress Syndrome). Clearly Elderberry should be avoided for those being hospitalized, unless one's doctor says otherwise.
 Also, for those who are in the "if a little is good, more is better" crowd, it might be suggested that you should limit your intake to the recommended dose.
 Nonetheless, I haven't found any medical sites which have said that healthy people should avoid Elderberry.