Despite the availability of numerous effective vaccines, the COVID-19 pandemic continues to exist globally. Scientists and medical professionals throughout the world are investigating every possible avenue to terminate the current pandemic. Povidone-iodine (PVP-I), particularly, has attracted much attention during this pandemic due to its virucidal activity against most upper respiratory tract infection (URTI) causing viruses, like adenovirus, rhinovirus, influenza, coxsackievirus, herpes simplex virus, coronavirus, and respiratory simplex virus¹.

Respiratory pathogens attach and colonize the oropharyngeal and nasopharyngeal mucosa to develop URTIs². Additionally, the protease enzymes involved in viral replication are found in the upper oro-digestive tract. Research has proved active viral replication in the throat by demonstrating the presence of viral replicative mRNA intermediates in throat-derived samples. Respiratory viruses often transmit via four major routes: direct (physical) contact, indirect contact (fomite), (large) droplets, and (fine) aerosols³. Additionally, an infected individual has the potential to shed the virus in exhaled breath droplets and aerosols during an acute viral respiratory infection. Studies have confirmed the critical role of aerosol transmission in the spread of SARS-CoV-2³. In line, it is reasonable that any measure 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 used in Asia for ages to treat URTIs by lowering the bacterial and viral load on oropharyngeal mucosa to decrease the transmission of diseases⁴. The efficacy of gargling 0.23% PVP-I mouthwash assessed in Japan showed efficacy in lowering the prevalence of URTIs compared with a placebo. This 0.23% concentration solution, when used in vitro on severe acute respiratory syndrome coronavirus and the Middle East Respiratory Syndrome Coronavirus, produced undetectable traces after 30 seconds of exposure⁵. Numerous clinical trials are still determining 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 shown by multiple modes of action that include disrupting microbial metabolic pathways and destabilizing the structural components of cell membranes, causing irreversible damage to the pathogen¹. 

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

Yet another study confirmed that nasal and oral antiseptic formulations of PVP-I (1% to 5% concentrations, respectively) effectively inactivate SARS-CoV-2 only after 60 seconds of exposure⁷.  

PVP-I has shown consistent results in reducing the viral load. It has been shown to destroy the ability of the SARS-CoV-2 lipid membrane and inactivate more than 99.99% of the virus within 30 seconds. All the commercial concentrations (0.5%, 1%, and 1.5%) have shown the same inactivation pattern within 15 seconds. Furthermore, this effect can 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. 

Thus, using PVP-I gargle and spray during the acute phase of infection is safe and can play a substantial role in preventing the spread of this virus. Viral inactivation not only prevents the person-to-person spread of URTIs but also diminishes the severity of the disease in patients by limiting the spread and decreasing the viral load delivered to the lungs. It may act as a strong arsenal in reducing 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.