The concerning new coronavirus called COVID-19 appears far more infectious and fast-spreading than typical flu viruses.

And COVID-19 appears more dangerous — especially to people aged over 60 years, who have underlying chronic health conditions, or who suffer from weakened immune systems.

Fortunately, COVID-19 doesn’t look very threatening for children, adolescents, and younger adults, who show either no symptoms or ones like those of a cold or the flu.

About 80% of COVID-19 cases — mostly the ones in younger people — are mild or asymptomatic, about 15% are severe, requiring supplemental oxygen, and about 5% are critical, requiring ventilation (i.e., use of a machine that does a patient’s breathing for them). 

The World Health Organization (WHO) currently estimates the average “crude mortality rate” — the number of deaths divided by the number of confirmed cases — at about 3.4%, but older people are at far greater risk of death than young people. 

Because testing for the virus has been slow, it's been hard to calculate the more important “case/fatality” rate — the number of reported deaths divided by the number of reported infections — for COVID-19. Experts suspect that its case/fatality rate may ultimately prove to be 1% or less — which would still be 10 times higher than the rate of 0.1% or lower for typical flu viruses.

Data reported from China in late February suggest a case/fatality rate of 0.2% among people under 40, which rose to 1.3% for people aged 50 to 59, to 3.6% for people aged 60 to 69, to 8% for people aged 70 to 79, and to 14.8% among people aged 80 or older. (The case/fatality rate in a given country or region will be affected by the availability and quality of its medical care.)

Prevention and treatment go hand in hand
As is appropriate in the early stage of a pandemic like COVID-19, much of the focus has been on containment via quarantines and behavior changes.

The U.S. Centers for Disease Control & Prevention (CDC) and other experts stress these antiviral steps:

  • Avoid touching your eyes, nose, and mouth.
  • Wash hands often with soap or an alcohol-based hand rub.
  • Avoid crowds and close contact with people — keep 6 feet away.
  • Clean and disinfect surfaces and objects people are likely to touch or otherwise contact.

So far, potential pharmaceutical and natural allies against COVID-19 and other viruses have received surprisingly little attention.

We reviewed some leading antiviral options — and focused on the most promising natural allies — last year in Credible Cold & Flu Remedies. And we address their potential to help fight COVID-19 below, under "Which nutrients might help fight flu and COVID-19?" and "Which foods and herbs might help fight flu and COVID-19?".

Before we get to potential natural allies, we’ll quickly review the infectious methods and key vulnerabilities of viruses, and report on a prospective anti-COVID-19 drug that's now being tested in clinical trials.

The infectious tools used by viruses are their weak spots
Viruses exploit the metabolic processes of the cells they invade to replicate themselves, then escape and spread to other cells.

To do that, a virus must do three things 1) attach to and penetrate a cell, 2) replicate itself, and then 3) exit the cell.

Accordingly, scientists seeking to develop antiviral drugs have focused on those three points of vulnerability — here’s how a drug or natural substance can stop a virus at one of those three points in the infection process:

1) Viral Infection via Hemagglutinin or HA: A virus uses this protein to attach to and invade a cell, in a process called hemagglutination. Once inside, a virus uses a cell’s own mechanisms to replicate itself in large numbers.

Anything that interferes with viral hemagglutination is referred to as a hemagglutinin inhibitor or HAI. Some natural substances are HAIs, and scientists have been trying to develop HAI drugs.

2) Viral Replication: Once inside an infected cell, viruses employ a polymerase enzyme to replicate themselves. (Gene scientists use polymerase to replicate DNA and RNA.) Certain drugs and natural substances that act as “nucleotide analog inhibitors” can inhibit the polymerase-mediated process of viral replication.

3) Viral Exit via Neuraminidase or NA: Once a virus has entered a cell and replicated itself, the viral progeny use the neuraminidase enzyme to open the wall of the infected cell so that they can infect more cells. Drugs (e.g., Tamiflu) and natural substances (e.g., black elderberry) that inhibit or “block” the viral neuraminidase enzyme are called neuraminidase inhibitors or NAIs. However, the effectiveness of NAIs varies and viruses can develop resistance to them.

There isn't much hope that NAIs will effectively treat COVID-19 cases, because NAI drugs like Tamiflu didn’t do much for people sickened by the SARS and MERS coronaviruses, which resemble COVID-19.

A possible pharmaceutical remedy for COVID-19?
Remdesivir or RDV is a relatively new antiviral drug that prevents viruses from replicating inside infected cells. First developed to treat the blood-borne Ebola and Marburg viruses, RDV appears effective against coronaviruses, including MERS and SARS.

Clinical trials testing the efficacy of remdesivir against COVID-19 are currently underway in the U.S. and China — with their initial results expected in April — and trials will soon begin in other Asian countries.

And the first time use in the U.S. against COVID-19 looked quite successful — although it’s not clear how effective it was, because the patient’s viral levels were already dropping before he got the drug (Holshue ML et al. 2020).

With “compassionate use” permission from the FDA, the drug’s maker, Gilead Science, provided remdesivir (RDV) to CDC, hospital, and university physicians treating an American COVID-19 patient — a middle-aged man who’d returned from China and was suffering respiratory symptoms — in Snohomish County, Washington.

The medical team started treating the man with intravenous RDV — the only form currently available — on the evening of hospital day seven (the 11th day of symptoms) with no adverse side effects.

Encouragingly, the patient was much better by the next day — he no longer needed supplemental oxygen, his lungs cleared, his fevered dropped, his appetite improved, and he became symptom-free, aside from an intermittent, diminishing dry cough and runny nose.

Of course, as the physicians who reported his case wrote, “… randomized controlled trials are needed to determine the safety and efficacy of remdesivir … for treatment of patients with 2019-nCoV [COVID-19] infection.” (Holshue ML et al. 2020)

And while successful intravenous treatment is good, it remains to be seen whether an oral version of RVD can be effective and made available.

We should note that scientists see some anti-COVID-19 promise in the anti-malarial drug chloroquine, although evidence confirming or denying that hope may take months to appear.

Which nutrients might help fight flu and COVID-19?
The first priority is to ensure that the body’s immune system has the nutrients it needs, either to fight infections or control its inflammation response.

Although many combine to yield optimal immune response, the key nutrients include vitamin D, selenium, zinc, and omega-3 fatty acids — with vitamin D being a fundamental antiviral ally.

As it happens, fatty fish like salmon, sablefish, Chilean seabass, albacore tuna and sardines are the top food sources of vitamin D — with wild salmon topping the list and beating farmed salmon on this score — and omega-3s, and are leading sources of selenium.

Seafood-source omega-3 fatty acids
Metabolic byproducts of omega-3 DHA — produced when we eat seafood or take fish or algal oil — are shown to suppress replication of some, possibly many or most, flu viruses (Bryant PA et al. 2004; Imai Y 2015).

And seafood-source omega-3 fatty acids (DHA and EPA) are critical to the body’s ability to end or “resolve” unnecessary and damaging inflammation — as in the “cytokine storms” that killed many relatively young, healthy people during the 1918 Spanish flu pandemic.

In addition, the excess of omega-6 fatty acids (mostly from cheap vegetable oils) in the standard American diet promotes inflammation, so it pays to avoid those oils and foods laden with them, while boosting your intake of omega-3s from seafood and/or supplemental fish oils. For more on that critical but overlooked nutritional aspect of immune-system health, see our Omega-3/6 Balance page.

Vitamin D
This hormone-like nutrient is an essential part of the body’s “innate” immune system — our first line of defense against pathogenic viruses and microbes — and is essential to the body’s ability to identify and kill microbial invaders: see Vitamin D Activates Two Key Immune Systems.

Vitamin D is an especially important ally in the lungs, where flu viruses — and, apparently, COVID-19 — tend to settle first. See Vitamin D May Explain the Flu … and Fight it, Too, in which we reviewed evidence linking seasonal flu epidemics to seasonal, darkness-related deficiencies of vitamin D. In fact, the CDC admits that no alternative hypotheses explain the seasonal nature of flu.

Epidemiological and clinical studies suggest that higher blood levels of vitamin D help prevent respiratory infections, as we reported in Vitamin D Cuts Flu Rate in First Clinical Trial, Flu and Colds Risk Linked to Vitamin D Lack, Vitamin D Lack Linked to Kids' Flu and Colds Risk, and Vitamin D Bolsters Lung Defenses.

Most importantly, a recent review of the clinical evidence — covering 25 trials involving 11,321 participants of all ages — showed that supplemental vitamin D reduces the risk for respiratory infections, especially among people with low vitamin D blood levels.

Some of the trials covered by the review found no preventive benefit. However, as the authors wrote, “Vitamin D supplementation … protected against acute respiratory tract infection overall.” (Martineau AR et al. 2017)

Vitamin D can also help prevent a potentially deadly overreaction by the immune system, in the form of a “cytokine storm” that triggers wildly excessive inflammation and fills a patient’s lungs with fluid: see Vitamin D May Explain the Flu … and Fight it, Too and Vitamin D Lack May Promote Sickening Inflammation.

Although it has shown anti-flu promise in clinical trials it doesn’t necessarily help prevent or treat the common cold. For more than that, see Friendly Bugs Cut Colds; Vitamin D Defeated.

However, vitamin D is not a panacea. Although it has shown anti-flu promise in some small clinical trials — but not others — it doesn’t appear to help prevent or treat the common cold, which, like COVID-19 is a coronavirus. For more than that, see Friendly Bugs Cut Colds; Vitamin D Defeated.

Leading vitamin D researchers believe that it makes good sense to take ample daily doses of vitamin D (i.e., 1-2,000 IU) to help prevent cancer and osteoporosis, and that it can't hurt to start taking take larger doses — such as 4,000 to 5,000 IU daily — temporarily if you feel an infection coming on.

Which foods and herbs might help fight flu and COVID-19?
As Hippocrates of ancient Greece reportedly said, “let food be your medicine”.

We answered a common question affirmatively in Do Foodborne Antioxidants Fight Viruses?, which covered growing evidence of antiviral benefits from the antioxidants that abound in fruits, vegetables, culinary and medicinal herbs, nuts, seeds, whole grains, cocoa, coffee, tea, and more.

Promising herbal antiviral prospects include four traditional medicinal plants, which are widely available as dietary supplements:

Some of these herbs appear to act as NAIs, others to possess HAI properties, and some appear to possess both antiviral properties.

Black elderberry (Sambucus nigra)
The active NAIs in black elderberry extract are specific flavonoid-type antioxidants. Flavonoids in black elderberry also appear to act as antiviral HAIs.

Turmeric root features three yellow-orange antioxidant pigments — collectively called curcumin — that appear to exert antiviral HAI effects, alongside its anti-inflammatory, brain-health, and anti-cancer effects.

Goldenseal (Hydrastis canadensis)
Goldenseal is rich in berberine, an anti-diabetic, antimicrobial alkaloid that appears to possess antiviral NAI properties.

Andrographis (Andrographis paniculata) – called creat, green chireta, and chuan xin lian
This herb has shown promise against cold viruses — about 20% of which are coronaviruses, the remainder being rhino viruses, RSV, and parainfluenza — in preliminary clinical trials.
Its antiviral compounds include andrographolides such as AL-1, which — in test tube and animal studies — inhibits avian influenza A (H9N2 and H5N1) and human H1N1 influenza A viruses.



  • Agostini ML, Andres EL, Sims AC, Graham RL, Sheahan TP, Lu X, Smith EC, Case JB, Feng JY, Jordan R, Ray AS, Cihlar T, Siegel D, Mackman RL, Clarke MO, Baric RS, Denison MR. Coronavirus Susceptibility to the Antiviral Remdesivir (GS-5734) Is Mediated by the Viral Polymerase and the Proofreading Exoribonuclease. mBio. 2018 Mar 6;9(2). pii: e00221-18. doi: 10.1128/mBio.00221-18.
  • BiopharmaDive. A closer look at the Ebola drug that's become the top hope for a coronavirus treatment. Accessed at /573261/
  • Chen DY, Shien JH, Tiley L, et al. Curcumin inhibits influenza virus infection and haemagglutination activity. Food Chem 2010;119:1346-51
  • Chen TY, Chen DY, Wen HW, Ou JL, Chiou SS, Chen JM, Wong ML, Hsu WL. Inhibition of enveloped viruses infectivity by curcumin. PLoS One. 2013 May 1;8(5):e62482. doi: 10.1371/journal.pone.0062482. Print 2013.
  • Enkhtaivan G, Muthuraman P, Kim DH, Mistry B. Discovery of berberine based derivatives as anti-influenza agent through blocking of neuraminidase. Bioorg Med Chem. 2017 Oct 15;25(20):5185-5193. doi: 10.1016/j.bmc.2017.07.006. Epub 2017 Jul 13.
  • Gordon CJ, Tchesnokov EP, Feng JY, Porter DP, Gotte M. The antiviral compound remdesivir potently inhibits RNA-dependent RNA polymerase from Middle East respiratory syndrome coronavirus. J Biol Chem. 2020 Feb 24. pii: jbc.AC120.013056. doi: 10.1074/jbc.AC120.013056.
  • Holshue ML, Washington State 2019-nCoV Case Investigation Team, et al. First Case of 2019 Novel Coronavirus in the United States. N Engl J Med, 382 (10), 929-936 2020 Mar 5. PMID: 32004427 DOI: 10.1056/NEJMoa2001191
  • Krawitz C, Mraheil MA, Stein M, Imirzalioglu C, Domann E, Pleschka S, Hain T. Inhibitory activity of a standardized elderberry liquid extract against clinically-relevant human respiratory bacterial pathogens and influenza A and B viruses. BMC Complement Altern Med. 2011 Feb 25;11:16. doi: 10.1186/1472-6882-11-16.
  • Martineau AR et al. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ. 2017 Feb 15;356:i6583. doi: 10.1136/bmj.i6583. Review.
  • Martineau AR et al. Vitamin D supplementation to prevent acute respiratory infections: individual participant data meta-analysis. Health Technol Assess. 2019 Jan;23(2):1-44. doi: 10.3310/hta23020.
  • Shen X, Zhang X, Liu S. Novel hemagglutinin-based influenza virus inhibitors. J Thorac Dis. 2013 Aug;5 Suppl 2:S149-59. doi: 10.3978/j.issn.2072-1439.2013.06.14.
  • World Health Organization (WHO). Coronavirus disease 2019 (COVID-19) Situation Report – 46. Accessed at
  • Worldometer. Age, Sex, Existing Conditions of COVID-19 Cases and Deaths. February 29, 2020. Accessed at
  • Wu X, Wu X, Sun Q, Zhang C, Yang S, Li L, Jia Z. Progress of small molecular inhibitors in the development of anti-influenza virus agents. Theranostics. 2017 Feb 8;7(4):826-845. doi: 10.7150/thno.17071. eCollection 2017. Review.
  • Ye M, Liao Y, Wu L, Qi W, Choudhry N, Liu Y, Chen W, Song G, Chen J. An Oleanolic Acid Derivative Inhibits Hemagglutinin-Mediated Entry of Influenza A Virus. Viruses. 2020 Feb 18;12(2). pii: E225. doi: 10.3390/v12020225.
  • Yu F, Wang Q, Zhang Z, Peng Y, Qiu Y, Shi Y, et al. (June 2013). Development of oleanane-type triterpenes as a new class of HCV entry inhibitors. J Med Chem. 56 (11): 4300–19. doi:10.1021/jm301910a. PMID 23662817.
  • Zakay-Rones Z, Thom E, Wollan T, Wadstein J. Randomized study of the efficacy and safety of oral elderberry extract in the treatment of influenza A and B virus infections. J Int Med Res. 2004 Mar-Apr;32(2):132-40.
  • Zakay-Rones Z, Varsano N, Zlotnik M, Manor O, Regev L, Schlesinger M, Mumcuoglu M. Inhibition of several strains of influenza virus in vitro and reduction of symptoms by an elderberry extract (Sambucus nigra L.) during an outbreak of influenza B Panama. J Altern Complement Med. 1995 Winter;1(4):361-9.