The oral cavity acts both as a portal of entry for the SARS-CoV-2 virus into the body as well as a reservoir for the virus.¹ The virus mainly replicates in the throat. A German study has shown that shedding of virus from the pharynx was very high during the first week after infection, with a peak at 7.11 × 10⁸ RNA copies per throat swab on the fourth day of the illness.² Asymptomatic individuals share viral load similar to that in the symptomatic patients making them potential sources of infection.³ Forty-four percent of secondary cases were infected during the presymptomatic stage of the index cases, in settings with significant household clustering, active case finding and quarantine outside the home.⁴

Reduction of the amount of the virus in the throat at the initial stage of infection, therefore, assumes utmost importance. Gargling is a traditionally practiced home remedy for sore throats and is a potentially useful strategy in controlling the COVID-19 pandemic.⁵ Its effectiveness in preventing upper respiratory infections among healthy people has been demonstrated in randomized trials.⁶

Gargling with an antiseptic such as povidone iodine (PVP-I) may help to break the chain of infection by reducing viral load in the throat and decreasing the amount of virus released in droplets.¹ PVP-I mouthwash is included in the WHO R&D Blueprint for Experimental Therapies against COVID-19.⁷   

PVP-I is a commonly used antiseptic and 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.” It has been reported as having the “highest virucidal activity profile among several antiseptics.”⁸ PVP-I has also demonstrated in vitro activity against the two related coronaviruses, the severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV).”⁹ Its multimodal action, lack of reported resistance and an excellent safety profile offer added advantage compared to other commonly available antiseptic agents.

In vitro studies have demonstrated virucidal activity of PVP-I against SARS-CoV-2, the virus which causes COVID-19.

A study investigating the in vitro virucidal activity of topical and oral PVP-I products against SARS-CoV-2 demonstrated rapid and effective virucidal activity of PVP-I against the virus. All four products tested in the study: 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 titer, within 30 seconds of contact.⁹ Another study demonstrated virucidal activity of PVP-I gargle and mouthwash against SARS-CoV-2 in just 15 seconds.¹⁰ In a study from Malaysia, 30 seconds, thrice-daily gargling with PVP-I led to 100% viral clearance within 4 days of the intervention (equivalent to 5 to 6 days after diagnosis), whereas gargling with essential oils for the same frequency and duration achieved 80% viral clearance, and tap water led to 20% viral clearance in patients with confirmed Stage 1 COVID-19 (asymptomatic state - first two days of infection).¹¹

Early viral clearance is very critical because COVID-19 is highly infectious at the early stage. Since PVP-I gargles have demonstrated early clearance of the virus, it has great potential to be part of the treatment and management of Stage 1 of the infection.¹¹

By decreasing the viral load in the throat and consequently droplet transmission, gargling decreases severity and incidence of infection.¹ It is a cost-effective preventive strategy and should be complementary to hand hygiene, masking, physical distancing that are routinely recommended for protection against COVID-19. Since we do not yet have a vaccine against COVID-19, these preventive measures should be strictly adhered to.

References

1. Herrera D, et al. Is the oral cavity relevant in SARS-CoV-2 pandemic? Clin Oral Investig. 2020;24(8):2925-30.
2. Wölfel R, et al. Virological assessment of hospitalized patients with COVID-2019. Nature. 2020;581(7809):465-9.
3. Zhou L, et al. SARS-CoV-2 viral load in upper respiratory specimens of infected patients. N Engl J Med 2020;382:1177-9.
4. He X, et al. Temporal dynamics in viral shedding and transmissibility of COVID-19. Nat Med. 2020;26:672-5.
5. Tsai C, et al. Possible beneficial role of throat gargling in the coronavirus disease pandemic. Public Health. 2020;185:45-6.
6. Satomura K, et al. Prevention of upper respiratory tract infections by gargling: a randomized trial. Am J Prev Med. 2005;29(4):302-7.
7. 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.
8. 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.
9. 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.
10. Hassandarvish P, et al. Povidone iodine gargle and mouthwash. Br Dent J. 2020;228(12):900.
11. Mohamed NA, et al. Early viral clearance among covid-19 patients when gargling with povidone-iodine and essential oils – a clinical trial. MedRxiv. September 9, 2020.

Dr KK Aggarwal

President CMAAO, HCFI and Past National President IMA