Natural antiviral agents to prevent upper respiratory infection

The world is currently experiencing another outbreak of deadly coronavirus. This novel strain coronavirus, called 2019-nCoV, was first identified on 7 Jan 2020 after causing several cases of pneumonia in Wuhan, the capital of Central China’s Hubei province. By 28 Jan 2020, the confirmed cases of this new coronavirus have reached 2801, with 2744 cases and eight deaths within China,  and a handful of cases found in 15 other countries among travellers from China [1]. 2019-nCov has sparked another wave of coronavirus epidemic in this century after severe acute respiratory syndrome coronavirus in 2002 (also known as SARS-CoV) and Middle East respiratory syndrome coronavirus (i.e. MERS-CoV) in 2012.

The world is currently experiencing another outbreak of deadly coronavirus.

Coronavirus is a type of virus that causes infection in the nose, sinuses, of upper throat, collectively known as the upper respiratory system. Common symptoms of upper respiratory infection include nasal congestion, cough, sore throat, and fever. There are many different sub-types of human coronaviruses, and most of them are not dangerous. However, coronaviruses that infect animals can evolve and make people sick and become a new human coronavirus. These evolved coronaviruses, such as the SARS-CoV, MERS-CoV, and 2019-nCoV, are potentially deadly to human [2], especially those who have a weakened immune system.

There is no treatment for coronavirus infections. We depend on the body’s immune system to fight off the viral infection. Therefore, the best way to prevent infection is to avoid exposure to the virus through maintaining hand and environmental hygiene and avoid contact with infected patients [2]. Keeping a strong and healthy immune system is also important. Here is a collection of natural anti-viral agents that can help to keep any risk of viral infection to the minimal.

Virus infection of a blood cell.

Colloidal silver

Colloidal silver refers to tiny particles of silver suspended in a liquid. It is an ancient remedy for treating bacterial, viral and fungal infections [3]. With the advent of technology, it is now possible to produce nanoparticles of silver in the range 1 – 100 nm in diameter. The small size of these particles enables the easy penetration of cells to target invading viruses. Silver nanoparticles have been shown to have antiviral effects through the various stages of virus replication with the host cells [3]. Silver nanoparticles have been proven to be active against several types of viruses, including human immunodeficiency virus, hepatitis B virus, herpes simplex virus, respiratory syncytial virus, and monkeypox virus [4]. Colloidal silver with nanoparticles is now widely available off-the-shelf as a home remedy.

TEM; Silver Nanoparticles (5978792602)

Vitamin C

Vitamin C is one of the most well-known anti-viral agents, especially against viruses causing the common cold. Vitamin C is known to prevent the common cold and shorten the duration of colds [5]. Against influenza virus, which triggers the common cold, vitamin C appears to be able to increase the production anti-viral cytokines interferon-alpha and beta [6]. These cytokines are signalling proteins of the immune system, which played both direct and indirect roles in destroying invading viruses. During the height of the SARS-CoV epidemic, vitamin C has been suggested as a potential treatment for reducing the risk of pneumonia in SARS patients [7].

Vitamin C pills.


Elderberry (Sambucus nigra) is a herb known to have antiviral, immune-enhancing, and antioxidant properties [8]. It has been shown to be effective against infectious bronchitis virus, a type of chicken coronavirus, by rendering the virus non-infectious during the early stage of infection [9]. It has also been shown to stimulate an immune response to prevent the infection by human influenza A virus [10].    

Black elderberry.


Echinacea is a traditional herb widely used in North America for the control of symptoms for common, influenza and other forms of infection. A standardised preparation of Echinacea purpurea has been tested active against all strains of human and avian influenza viruses tested (including a Tamiflu-resistant strain), as well as herpes simplex virus, respiratory syncytial virus, and rhinoviruses [11].  Echinacea can be a useful remedy against most viruses that trigger respiratory tract infection [12].  

Echinacea flowers.

Olive leaf

Olive leaf extract is a native Mediterranean remedy for the common cold. It contains oleuropein, a phenolic compound, which is an anti-viral agent. Oleuropein is active against many viruses, including herpes mononucleosis, hepatitis virus, rotavirus, bovine rhinovirus, canine parvovirus, feline leukaemia virus, respiratory syncytial virus and para-influenza type 3 virus [13]. A study among high school athletes reported that taking olive leaf extract can reduce the duration of upper respiratory infection, even though the incidence of upper respiratory infection did not reduce over a season [14].

Olive leaves.


Infection of the upper respiratory system can be caused by many viruses, including rhinovirus, influenza, and human coronavirus. The world is currently experiencing another outbreak of deadly coronavirus. Besides keeping hand hygiene and avoid contact with infected persons, it is also important to keep a healthy and strong immune system to prevent upper respiratory infection. Colloidal silver, vitamin C, elderberry, echinacea, and olive leaf extract are some natural anti-viral agents that can be potentially useful for the prevention of upper respiratory infections caused by viruses. Taking one or more of these supplements can be a useful preventive measure.  

Common cold is a form of upper respiratory infection caused by viruses.


[1]        J.L. Ravelo, 2019-nCoV outbreak — a timeline | Devex, (n.d.). (accessed January 28, 2020).

[2]        Coronavirus | Home | CDC, (n.d.). (accessed January 28, 2020).

[3]        A. Lansdown, Silver in Health Care: Antimicrobial Effects and Safety in Use, in: Curr. Probl. Dermatol., 2006: pp. 17–34. doi:10.1159/000093928.

[4]        S. Galdiero, A. Falanga, M. Vitiello, M. Cantisani, V. Marra, M. Galdiero, Silver nanoparticles as potential antiviral agents, Molecules. 16 (2011) 8894–8918. doi:10.3390/molecules16108894.

[5]        H. Hemilä, Vitamin C and Infections, Nutrients. 9 (2017) 339. doi:10.3390/nu9040339.

[6]        Y. Kim, H. Kim, S. Bae, J. Choi, S.Y. Lim, N. Lee, J.M. Kong, Y.-I. Hwang, J.S. Kang, W.J. Lee, Vitamin C Is an Essential Factor on the Anti-viral Immune Responses through the Production of Interferon-α/β at the Initial Stage of Influenza A Virus (H3N2) Infection, Immune Netw. 13 (2013) 70–74. doi:10.4110/in.2013.13.2.70.

[7]        H. Hemilä, Vitamin C and SARS coronavirus, J. Antimicrob. Chemother. 52 (2003) 1049–1050. doi:10.1093/jac/dkh002.

[8]        K. Bone, The Ultimate Herbal Compendium, Phytotherapy Press, Warwick, QLD, 2007.

[9]        C. Chen, D.M. Zuckerman, S. Brantley, M. Sharpe, K. Childress, E. Hoiczyk, A.R. Pendleton, Sambucus nigra extracts inhibit infectious bronchitis virus at an early point during replication, BMC Vet. Res. 10 (2014) 24. doi:10.1186/1746-6148-10-24.

[10]      E. KINOSHITA, K. HAYASHI, H. KATAYAMA, T. HAYASHI, A. OBATA, Anti-Influenza Virus Effects of Elderberry Juice and Its Fractions, Biosci. Biotechnol. Biochem. 76 (2012) 1633–1638. doi:10.1271/bbb.120112.

[11]      J. Hudson, S. Vimalanathan, Echinacea—A Source of Potent Antivirals for Respiratory Virus Infections, Pharmaceuticals. 4 (2011) 1019–1031. doi:10.3390/ph4071019.

[12]      J.B. Hudson, Applications of the phytomedicine Echinacea purpurea (Purple Coneflower) in infectious diseases, J. Biomed. Biotechnol. 2012 (2012) 769896. doi:10.1155/2012/769896.

[13]      S.H. Omar, Oleuropein in olive and its pharmacological effects, Sci. Pharm. 78 (2010) 133–154. doi:10.3797/scipharm.0912-18.

[14]      V. Somerville, R. Moore, A. Braakhuis, The Effect of Olive Leaf Extract on Upper Respiratory Illness in High School Athletes: A Randomised Control Trial, Nutrients. 11 (2019) 358. doi:10.3390/nu11020358.

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