The virucidal potential effects of violet-blue light on influenza D virus

Influenza D virus (IDV) is a novel influenza virus, first isolated from swine with influenza-like symptoms in the USA in 2011. To date, IDV circulation has been reported in various animal species such as cattle, pigs, horses with the ability to expand its range of hosts. UV radiation has been widely used for the disinfection of various sources such as water, air, and surfaces, especially in places at greater risk of contamination by viruses and bacteria, such as hospitals and health facilities. The aim of this study was to evaluate the potential virucidal effect of a violet-blue light against IDV. Viral suspension of IDV was exposed to a violet-blue light (405 nm) for different times (radiant exposures): 22 min and 30 s (5.4 J/cm²), 45 min (10.8 J/cm²), 90 min (21.6 J/cm²), 180 min (43.2 J/cm²), and 360 min (86.4 J/cm²), and different temperatures (room temperature, 4 and 37 °C). At the end of exposure, virus titration was performed on MDCK cells. After violet-blue light exposure, a viral titre reduction proportional to exposure time was observed: 0.228 log₁₀ after 22 min and 30 s, 0.668 log₁₀ after 45 min, 0.940 log₁₀ after 90 min, 1.375 log₁₀ after 180 min and 2.293 log₁₀ after 360 min. Differences were observed among temperatures of exposure, with the greatest virucidal effect observed at room temperature. As reported for other respiratory viruses, this violet-blue light can potentially be used to reduce IDV spread in potentially hotspot areas for animals and humans.