Sunlight Inactivation of Enveloped Viruses in Clear Water

Enveloped virus fate in the environment is not well understood; there are no quantitative data on sunlight inactivation of enveloped viruses in water. Herein, we measured the sunlight inactivation of two enveloped viruses (Phi6 and murine hepatitis virus, MHV) and a nonenveloped virus (MS2) over time in clear water with simulated sunlight exposure. We attenuated UV sunlight wavelengths using long-pass 50% cutoff filters at 280, 305, and 320 nm. With the lowest UV attenuation tested, all decay rate constants (corrected for UV light screening, k) were significantly different from dark controls; the MS2 k was equal to 4.5 m(2)/MJ, compared to 16 m(2)/MJ for Phi6 and 52 m(2)/MJ for MHV. With the highest UV attenuation tested, only k for MHV (6.1 m(2)/MJ) was different from the dark control. Results indicate that the two enveloped viruses decay faster than the nonenveloped virus studied, and k are significantly impacted by UV attenuation. Differences in k may be due to the presence of viral envelopes but may also be related to other differing intrinsic properties of the viruses, including genome length and composition. Reported k values can inform strategies to reduce the risk from exposure to enveloped viruses in the environment.