The SARS-CoV-2, which causes COVID-19, is highly contagious. Human-to-human transmission of the disease is the primary route of spread and occurs through respiratory droplets expelled during coughing, sneezing and talking when a person is in close contact (within 1 m) with a person who has the infection. There is no cure for COVID-19 and till an actual vaccine is available, adherence to preventive measures (wearing face mask, hand washing, physical distancing), which protect against the infection, is critical.

The mouth is also a portal of entry for the virus. Throat is a reservoir for the transmission of the virus, as the virus mainly replicates here, even in asymptomatic or presymptomatic persons, who become potential sources of infection. Gargling therefore is another important preventive measure to reduce the viral load in the throat of the infected patients. Although it will not eliminate the virus, it may reduce spread of the virus into the community.

Excerpts from published evidence

Broad spectrum antimicrobial action

“Povidone‐iodine is considered to have the broadest spectrum of antimicrobial action compared with other common antiseptics such as chlorhexidine, octenidine, polyhexanide and hexetidine showing efficacy against Gram‐positive and Gram‐negative bacteria, bacteria spores, fungi, protozoa and several viruses.”1

Potent virucidal activity

• “In addition to its broad antibacterial and antifungal activity, PVP-I has demonstrated in vitro activity against a range of viruses, including the related SARS-CoV and MERS-CoV.” 2
• “Povidone‐iodine has been reported as having the highest virucidal activity profile among several antiseptics such as CHG, benzalkonium chloride (BAC), BEC and alkyldiaminoethyl‐glycine hydrochloride (AEG). Using a standardised in vitro approach, PVP‐I gargle was found to inactivate a panel of viruses that included adenovirus, mumps, rotavirus, poliovirus (types 1 and 3), coxsackie virus, rhinovirus, herpes simplex virus, rubella, measles, influenza and human immunodeficiency virus.” 1
• “PVP-I gargle/mouthwash diluted 1:30 (equivalent to a concentration of 0.23% PVP-I) showed effective bactericidal activity against Klebsiella pneumoniaeand Streptococcus pneumoniae and rapidly inactivated SARS-CoV, MERS-CoV, influenza virus A (H1N1) and rotavirus after 15 s of exposure.” 3
• “Viral infectious titers were reduced to levels below the detection limits by incubation for only 10 s with the PVP-I products used in this study. These results indicate that PVP-I products have virucidal activity against avian influenza A viruses.” 4

Virucidal activity against SARS-CoV-2 virus: In vitro evidence

• “All four products [antiseptic solution (PVP-I 10%), skin cleanser (PVP-I 7.5%), gargle and mouth wash (PVP-I 1%) and throat spray (PVP-I 0.45%)] achieved ≥ 99.99% virucidal activity against SARS-CoV-2, corresponding to ≥ 4 log10 reduction of virus titre, within 30 s of contact. This study provides evidence of rapid and effective virucidal activity of PVP-I against SARS-CoV-2.” 2
• In a Letter to Editor published in the British Dental Journal, Hassandarvish et al have given evidence of the in vitro virucidal activity of an oral PVP-I product against the SARS-CoV-2 virus. They write, “In our study, we present direct evidence of the virucidal activity of PVP-I gargle and mouthwash against SARS-CoV-2 in just 15 seconds. The study demonstrated that undiluted PVP-I achieved >5 log10 reduction in the virus titres at 15, 30 and 60 seconds treatment exposure under both clean and dirty conditions. In contrast, when PVP-I was tested at 1:2 dilution a >4 log10 kill at 15 seconds and >5 log10 kill at 30 and 60 seconds in comparison to control was seen in both clean and dirty.” 5

PVP-I mouthwash is included in the WHO R&D Blueprint for Experimental Therapies against COVID-19. 6  

Rationale for throat gargling in COVID-19 pandemic

• “SARS-CoV-2 shows tropism for the throat tissue, which is associated with disease transmission and severity.” 7
• “The viral load that was detected in the asymptomatic patient was similar to that in the symptomatic patients, which suggests the transmission potential of asymptomatic or minimally symptomatic patients.” 8
• “We observed the highest viral load in throat swabs at the time of symptom onset, and inferred that infectiousness peaked on or before symptom onset. We estimated that 44% (95% confidence interval, 30–57%) of secondary cases were infected during the index cases’ presymptomatic stage, in settings with substantial household clustering, active case finding and quarantine outside the home.” 9
• “It is therefore imperative to reduce the viral load in oropharynx with adequate oral prophylactic measures.” 10
• “Thus, throat gargling... might be potentially useful in controlling the COVID-19 pandemic.” 7 “This intervention is not intended to cure the disease but may significantly and dramatically reduce viral spread into the community and workplaces.” 11
• Ricardo AP Persaud writes in an article in the Online Journal of Otolaryngology & Rhinology, “In my opinion, P-I is the new PPE and its topical usage in nose, oral cavity and pharynx is now one of the best ways to flatten the Curve of Covid-19, especially in countries like USA, India and Brazil.” 12

References

1. Kanagalingam J, et al. Practical use of povidone‐iodine antiseptic in the maintenance of oral health and in the prevention and treatment of common oropharyngeal infections. Int J Clin Pract. 2015;69:1247–56.
2. Anderson DE, et al. Povidone-iodine demonstrates rapid in vitro virucidal activity against SARS-CoV-2, the virus causing COVID-19 disease. Infect Dis Ther. 2020:1–7.
3. Eggers M, et al. In vitro bactericidal and virucidal efficacy of povidone-iodine gargle/mouthwash against respiratory and oral tract pathogens. Infect Dis Ther. 2018;7(2):249–59.
4. Ito H, et al. Outbreak of highly pathogenic avian influenza in Japan and ant-influenza virus activity of povidone-iodine products. Dermatology. 2006;212(Suppl 1):115–8.
5. Hassandarvish P, et al. Povidone iodine gargle and mouthwash. Br Dent J. 2020;228(12):900.
6. WHO R&D Blueprint COVID 19 Experimental Treatments: World Health Organisation. 2020. Available at: https://www.who.int/docs/default-source/coronaviruse/covid-classification-of-treatment-types-rev.pdf, Accessed 30.7.20.
7. Tsai C, et al. Possible beneficial role of throat gargling in the coronavirus disease pandemic. Public Health. 2020;185:45-6
8. Zhou L, et al. SARS-CoV-2 viral load in upper respiratory specimens of infected patients. N Engl J Med 2020;382:1177-9.
9. He X, et al. Temporal dynamics in viral shedding and transmissibility of COVID-19. Nat Med. 2020;26:672-5.
10. Pattanshetty S, et al. Povidone-iodine gargle as a prophylactic intervention to interrupt the transmission of SARS-CoV-2. Oral Dis. 2020;10.1111/odi.13378.
11. Mendoza L. Prevention of COVID-19 Infection with Povidone-Iodine (April 30, 2020).Available at SSRN:https://ssrn.com/abstract=3589404 or http://dx.doi.org/10.2139/ssrn.3589404
12. Ricardo AP Persaud. Povidone-Iodine may be the “Silver Bullet” in the Prevention and Control of Covid-19 Infection, Based on New Scientific Data. On J Otolaryngol & Rhinol. 3(1): 2020.

Dr KK Aggarwal

President CMAAO, HCFI and Past National President IMA