Mouthwash can reduce oral COVID-19 virus load

As we are all aware of human to human transmission of COVID-19 has been reported to occur through close contact with an infected person. This could be through exposure to coughing, sneezing, breathing drops or airborne particles of an infected person. Therefore, taking safety precautions such as using hand hygiene, wearing masks and maintaining social distancing are essential practices to control public infections. According to a previous study the detection rate of SARS-CoV-2 has been higher in saliva than nasopharyngeal swabs. And as discovered by research studies 91.7% of the COVID-19 patients showed symptoms of contracting the COVID-19 virus. In addition to that the RNA of COVID-19 in saliva from infected individuals have been found to be stable at 4°C, room temperature and 30°C for prolonged periods.  Therefore, Saliva is playing an important role in transmitting the infection through infected droplets. 

Aerosols are liquid or solid particles (less than 5 μm) and remain suspended in the air for long periods. They evaporate faster and spread wide in the air and fall out.  There are larger droplets (more than 5 μm) that are heavier and fall out nearby faster than they evaporate, hence they are unable to stay suspended for long periods. Virus-carrying aerosols can penetrate the healthy human body and lungs through direct inhalation; through the nose or mouth. Moreover, the throat is a major site of replication and shedding of the virus in COVID-19 illness. Virus particles are abundant in the throat and the sputum. The virus peak 5-6 days after symptom onset and decline thereafter.

There are at least three (03) different pathways which are reasons for the presence of COVID-19 in saliva namely; 
The COVID-19 virus in the lower and upper respiratory tract enters the oral cavity together with the liquid droplets. 
COVID-19 present in the blood can access the mouth via Crevicular fluid, an oral cavity specific exudates that contain local proteins derived from extracellular matrix and serum derived proteins.

Another way for COVID-19 to occur in the oral cavity is by major and minor salivary gland infection with subsequent release of particles in saliva via salivary ducts.

The Coronavirus is surrounded by a fatty layer which is called a lipid envelope that presents a typical structure with the “spike protein” in its membrane envelope. The interaction between this protein and angiotensin-converting enzyme 2 (ACE2) receptors which are responsible for the entry of the virus into host cells. The ACE2 receptors are distributed in different parts of the body. They may indicate possible routes of the infection. The membrane bound to ACE2 is found in different tissue cells, such as mucosal tissues, gingiva, non-keratinizing squamous epithelium, and epithelial cells of the tongue and salivary glands. Research studies have suggested that the Coronavirus transmission can be closely connected with saliva interactions making oral tissues a possible reservoir from which SARS-CoV-2 transmission may occur during coughing, sneezing, talking and even during dental care.When the virus enters into the host viral proteins are incorporated into host cell proteins to create the shed viral particle. 

Mouth washes are widely used as mouth rinsing chemical solutions, especially before oral surgery, due to its ability to reduce the number of microorganisms in the oral cavity. Hence, The Centre for Disease Control and Prevention (CDC) has recommended the use of mouthwashes before oral procedures. Moreover, recent research studies made an attempt to check whether there is a positive effect of commercially available mouth rinsing liquid on reducing  the COVID-19 oral virus load since saliva plays a significant role in corona virus transmission. Few studies have discovered that commercially available mouth washes have persistent effect in reducing of SARS-CoV-2 (COVID-19) viral load in saliva compared to water. Because, Broad-spectrum antimicrobial mouthwashes are one of the most available solutions to reduce oral pathogens.

According to research studies, commercially available mouth washes contain different active components namely, Dequalinium Chloride/ Benzalkonium Chloride, Chlorhexidine, Polyvidone-Iodine, Alkyl Dimethyl Glycine and Alkyl Dimethyl Amine Oxide, Ethanol And Essential Oil (Thymol, Menthol and Eucalyptol) which have the ability to reduce the SARS-CoV-2 viral load significantly to undetectable level. 

Vitro studies have discovered the effect of Chlorhexidine on several viruses, such as the SARS virus, from a Coronavirus infected family on reducing the viral load. Results of these studies proved that varying concentrations of Chlorhexidine kill the enveloped viruses.  In addition to that a mixture of Alkyl Dimethyl Glycine and Alkyl Dimethyl Amine Oxidealso has antiviral activity against enveloped viruses. Because, this agent can adhere to the surface of microorganism through the polar head group of the Amine Oxide-Betaine mixture and subsequently disrupt the microbial membrane with the Alkyl portion of the molecule. Therefore, previous studies have indicated mouthwash which contains a mixture of alkyl dimethyl glycine and Alkyl Dimethyl Amine Oxide increases oral hygiene and reduces the transmission of the seasonal flu-virus. Hence, concerning this evidence and mechanism of action, it is probable that mouthwash can be effective in reducing the oral microorganisms of patients with COVID-19.

Moreover, Polyvinylpyrrolidone (PVP) is a type of antiviral compound uses in mouth wash. It has free iodine and it releases gradually. Antiviral function of Polyvinylpyrrolidone is done by oxidation of amino acids and nucleic acids and it damages the microorganism by disturbingto various metabolic pathways and destabilization of the cell membrane. A hospital study on COVID-19 has recommended the use of mouthwash which contains Polyvinylpyrrolidone for patients and staff of the health department who are in direct contact with COVID-19 patients since it reduces the risk of the virus spreading during coughing, sneezing, and even talking, and it may thus be effective in controlling the COVID-19 outbreak. 

Furthermore, recent research work confirms the antiviral effectiveness of Listerine mouthwash  which contains several essential oil components such as Thymol, Menthol, And Eucalyptolagainst enveloped virus. 

According to above mentioned factors, oral wash with mouth rinsing can be consider as a safety precaution during this COVID-19 outbreak. 

(The writer holds a MSc. Degree in Industrial and Environmental Chemistry from the University of Kelaniya and a BSc in Food Production and a Technology Management degree
from the Wayamba University of Sri Lanka)