Despite the growing availability of effective vaccines, the COVID-19 pandemic continues to rage worldwide. To halt the current pandemic, scientists and medical professionals worldwide are exploring every possible avenue. Interest in povidone-iodine (PVP-I) has surged during this pandemic following its virucidal activity against most upper respiratory tract infection (URTI) causing viruses, such as adenovirus, rhinovirus, influenza, coxsackievirus, herpes simplex virus, coronavirus, and respiratory simplex virus¹.

Respiratory pathogens adhere to and colonize the oropharyngeal and nasopharyngeal mucosa to develop URTIs². In addition, the protease enzyme involved in viral replication is present in the upper oro-digestive tract. Active viral replication in the throat has also been confirmed by the presence of viral replicative mRNA intermediates in throat-derived samples. 

Respiratory viruses usually transmit via four major modes of transmission: direct (physical) contact, indirect contact (fomite), (large) droplets, and (fine) aerosols³. In addition, an infected individual may shed virus in exhaled breath droplets and aerosols during an acute viral respiratory infection. Many studies concluded that aerosol transmission plays a critical role in the spread of SARS-CoV-2³. Considering the above, it is rational that any measures to remove or reduce the viral load in the nose, pharynx, and mouth would help to prevent contamination and community transmission.

Diluted PVP-I solutions have been historically used in Asia to treat URTIs by decreasing the bacterial and viral load on oropharyngeal mucosa to decrease the transmission of diseases⁴. The efficacy of gargling 0.23% PVP-I mouthwash in Japan was efficacious in lowering the prevalence of URTIs compared with placebo. The 0.23% concentration was used in vitro on severe acute respiratory syndrome coronavirus and the Middle East Respiratory Syndrome Coronavirus, which produced undetectable traces after 30 seconds of exposure⁵. Numerous clinical trials are being conducted to determine if there is a decrease in viral load and, resultant, transmission when using oral or nasal topical PVP-I in COVID-19 patients⁴.

The strong anti-microbicidal activity of PVP-I is expressed by multiple modes of action that include the disruption of microbial metabolic pathways and destabilization of the structural components of cell membranes, causing irreversible damage to the pathogen¹. 

An in-vitro study reported that povidone-iodine nasal antiseptic solutions at concentrations as low as 0.5% rapidly inactivate SARS-CoV-2 at contact times as short as 15 seconds⁶. 

Another study confirmed that nasal and oral antiseptic formulations of PVP-I (1% to 5% concentrations, respectively) are effective in inactivating SARS-CoV-2 only after 60 seconds of exposure7.  

PVP-I, however, showed more consistent results in reducing the viral load. It shows the destruction ability of the SARS-CoV-2 lipid membrane, and it inactivated more than 99.99% of the virus within 30 seconds. All the commercial concentrations (0.5%, 1%, and 1.5%) showed the same inactivation pattern within 15 seconds. Its effect was found to extend up to at least three hours, and it can be used safely for up to six months in the oral cavity and five months in the nasal cavity⁸. 

In summary, using PVP-I gargle during the acute phase of infection is safe and may have a substantial role in preventing the spread of this virus. Viral inactivation may not only prevent the person-to-person spread of URTIs but may also diminish the severity of disease in patients by limiting the spread and decreasing the viral load delivered to the lungs. It may act as a strong arsenal in mitigating viral transmission beyond personal protective equipment⁴. 

References

1. 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.
2. J Van Schoor, Colds, flu and coughing: over-the-counter products for pharyngitis and tonsillitis, South African Family Practice, (2013) 55:4, 330-333, DOI: 10.1080/20786204.2013.10874371
3. Leung, Nancy H L. “Transmissibility and transmission of respiratory viruses.” Nature reviews. Microbiology vol. 19,8 (2021): 528-545. doi:10.1038/s41579-021-00535-6.
4. Khalil I, Barma P (2020) Povidone Iodine (PVP-I) mouth gargle/nasal spray may be the simplest and cost effective therapeutic antidote for COVID-19 Frontier. Arch  Community Med Public Health 6(2): 138-141. DOI: https://dx.doi.org/10.17352/2455-5479.000093
5. Kanagalingam J, Feliciano R, Hah JH, et al. Practical use of povidone-iodine antiseptic in the maintenance of oral health and in the prevention and treatment of common oropharyngeal infections. International Journal of Clinical Practice. 2015 Nov;69(11):1247-1256. DOI: 10.1111/ijcp.12707.
6. Frank, Samantha et al. “Povidone-Iodine Use in Sinonasal and Oral Cavities: A Review of Safety in the COVID-19 Era.” Ear, nose, & throat journal vol. 99,9 (2020): 586-593.
7. Pelletier, Jesse S et al. “Efficacy of Povidone-Iodine Nasal and Oral Antiseptic Preparations Against Severe Acute Respiratory Syndrome-Coronavirus 2 (SARS-CoV-2).” Ear, nose, & throat journal vol. 100,2_suppl (2021): 192S-196S. doi:10.1177/0145561320957237
8. Hernández-Vásquez A, Barrenechea-Pulache A, Comandé D, Azañedo D. Mouthrinses and SARS-CoV-2 viral load in saliva: a living systematic review. Evid Based Dent. 2022 May 24:1–7. doi: 10.1038/s41432-022-0253-z.