AbstractObjective: The Covid-19 pandemic has highlighted the importance of aerosolized droplets inhaled into the nose in the transmission of respiratory viral disease. Inactivating pathogenic viruses at the nasal port of entry may reduce viral loads, thereby reducing infection, transmission and spread. In this communication, we demonstrate safe and broad anti-viral activity of oil-in-water nanoemulsion (nanodroplet) formulation containing the potent antiseptic 0.13% Benzalkonium Chloride (NE-BZK). Results: We have demonstrated that NE-BZK exhibits broad-spectrum, long-lasting antiviral activity with >99.9% in vitro killing of enveloped viruses including SARS-CoV-2, human coronavirus, RSV, and influenza B. In vitro and ex-vivo studies demonstrated continued killing of >99.99% of human coronavirus with diluted NE-BZK and persistent for 8 hours post application, respectively. The repeated application of NE-BZK, twice daily for 2 weeks into rabbit nostrils demonstrated its safety with no nasal irritation. These findings demonstrate that formulating BZK into the proprietary nanodroplets offers a safe and effective antiviral and a significant addition to strategies to combat the spread of respiratory viral infectious diseases.