Background Information


PI and CHG are being used as antiseptic preventive interventions to decolonize patients’ skin and nares to reduce infections, and as both PI and CHG have broad-spectrum viricidal activity, we hypothesize that antiseptic application of topical nasal PI and oral CHG can protect naso-oropharyngeal viral colonization in essential workers, reducing acquisition of SARS-CoV-2 and subsequent COVID-19 infection.


Total positive COVID-19 case count in Wisconsin:  570,412

(, March 16th, 2021)

On March 11, 2020 the World Health Organization declared the novel coronavirus(COVID-19) outbreak a global pandemic. The emergence of the  novel human coronavirus SARS-CoV-2 (COVID-19) pandemic is a recent example of a deadly virus having significant health effects with its associated high morbidity and mortality.  As of January 11, 2021, over 22 million people in the United States have been infected with COVID-19 with over 370,000 deaths. 

Current scientific consensus is that SARS-CoV-2 spreads primarily by entering a person’s nose and/or mouth.  Close contact (within about 6 feet) with an infected person increases the likelihood of transmission.  Evidence also suggests transmission can occur from asymptomatic or pre-symptomatic individuals – complicating efforts to contain spread of the virus.  Non-pharmaceutical interventions (NPIs) are the first line of defense, especially until vaccination is widely available for a novel virus.  These NPIs include social distancing and hygienic practices such as personal protective measures for everyday use (e.g., voluntary home isolation of ill persons, respiratory etiquette, and hand hygiene); personal protective measures reserved for influenza pandemics (e.g., voluntary home quarantine of exposed household members and use of face masks in community settings when ill); community measures aimed at increasing social distancing (e.g., school closures and dismissals, social distancing in workplaces, and postponing or cancelling mass gatherings); and environmental measures (e.g., routine cleaning of frequently touched surfaces).

In the absence of evidence-based treatments and/or widely available vaccinations for SARS-CoV-2, the community is limited to NPIs to reduce infections and mortality.   Minimizing transmission of the disease through NIPs is especially critical with the COVID-19 pandemic due to the high percentage of patients who need hospitalization and/or critical care.  Severe disease (dyspnea, hypoxia, or >50% lung involvement on imaging) or critical disease (respiratory failure, shock, or multi-organ system dysfunction) occurs in approximately 20% of diagnosed COVID-19 cases.  Due to the severity of these symptoms, patients often require critical care in the intensive care unit and the use of specialized lifesaving equipment, such as mechanical ventilation.

Need to Protect Essential Workers

Essential workers who cannot work remotely are at increased risk of COVID-19 due to their exposure to the public.  Measures such as hand hygiene and use of personal protective equipment (such as face masks) are key infection control tools for essential workers.  We hypothesize that use of nasal and oral decolonization with Pi and CHG can further reduce the risk of acquiring SARS-COV-2 infection by coating the nasal and oral pharynx with an antiseptic.  If so, we expect to see a reduction in the development of COVID-19 illness among those using a PI and CHG intervention.

(Photo by Bryce Richter / UW-Madison)

Povidone Iodine and Chlorhexidine as COVID-19 Antiseptic Agents

The skin and mucous membranes are considered first line of defense against infection and harbor both beneficial and pathogenic microorganisms. Often, life-saving medical treatments, especially invasive procedures, interrupt this first line of defense. A common infection prevention strategy is to disinfect the skin or mucous membrane prior to medical procedures to prevent infections.

Antiseptics have been extensively used in healthcare settings to disinfect skin, mucous membranes and wounds to kill microorganisms that may cause infections. There is a wide variety of chemical agents (or biocides) that can be used at antisepsis, many which have been used for hundreds of years. Povidone iodine (PI) and chlorhexidine gluconate (CHG) are two common antiseptics that have been used safely in healthcare for over 50 years. CHG and PI skin antisepsis have long been used prior to surgery and other invasive procedures. More recently, CHG has been used to decolonize skin and oropharynx of critically ill patients with invasive devices (e.g., central lines and mechanical ventilation). In addition, application of nasal PI is being used for bacterial decolonization of nares prior to surgery. CHG and PI are also used extensively in hand antisepsis in healthcare. Antiseptics have a broad spectrum of activity and have multiple nonspecific cellular targets. Despite widespread use, antiseptic resistance is not common. PI and CHG are known to be safe, effective, affordable and have minimal adverse effects.

Both PI and CHG show rapid, long-lasting virucidal activity.  Recent in vitro evidence suggests that PI can effectively inhibit multiple viruses, including the coronaviruses SARS-CoV-2, SARS-CoV, and MERS-CoV.  Preliminary evidence suggests that oral rinses and gargling with PI or CHG may reduce the incidence of respiratory infections.

Given this evidence, antiseptic decolonization of the nose and mouth with PI and CHG is a topic of growing interest.  Some medical practices have recommended prophylactic use of PI and CHG in patients to reduce transmission of SARS-CoV-2 during medical procedures.  Initial pilot studies into safety of nasal and oral decolonization with PI specifically for the purposes of reducing COVID-19 transmission have found that nsal and oral application is generally tolerable and safe.

Initial in vivo studies found that PI and CHG mouthwashes reduced SARS-CoV-2 viral loads in the saliva.  These studies initial data suggestion are promising.  While it remains unclear from this work whether the observed reduction in viral loads had a clinical impact, our understanding of COVID-19 transmission and infection suggests a potential role for reducing the viral load on illness severity.

Our study will demonstrate if a PI and CHG treatment if effective in reducing SARS-CoV-2 viral loads and COVID-19 diagnoses.  If so, use of PI and CHG may be an effective addition to other infection control practices (like hand washing and mask wearing) to prevent COVID-19