Data associated with "Influence of Carbon Dioxide and pH on Influenza Virus in Saliva Droplets"

Upon exhalation, virus-laden respiratory droplets experience rapid changes in environmental conditions that lead to chemical and physical alterations that can affect virus infectivity. By manipulating the atmosphere surrounding sessile saliva droplets, we altered their chemistry and then assessed the impacts of these changes on the infectivity of influenza A virus. Differences in virus inactivation were small in high carbon dioxide in nitrogen (4.3-5% CO2 in N2) vs. ambient air (0.04% CO2). In low CO2 (<0.005% CO2 in N2), inactivation was greater than in ambient air at 55% relative humidity (RH) and lesser at 80% RH. Collectively, these results suggest that the driving factors for virus inactivation vary with RH. We measured droplet pH using gold nanoprobes in combination with surface enhanced Raman spectroscopy (SERS) and found that pH increased in low CO2 and decreased in high CO2 at 80% RH by ~1 pH unit in both cases. Results were consistent with chemical equilibrium modeling, which indicated that both carbonate and phosphate buffering were important. Changes in pH were smaller or insignificant at 30% and 55% RH. At these low and medium RHs, rapid evaporation of water from the droplets and the resulting increase in viscosity may limit changes in pH. Measured changes in pH did not appear to be sufficient to drive virus inactivation under any tested condition.