Previous studies have demonstrated that SARS-CoV-2 is stable on surfaces for extended periods under indoor conditions. In the present study, simulated sunlight rapidly inactivated SARS-CoV-2 suspended in either simulated saliva or culture media and dried on stainless steel coupons. Ninety percent of infectious virus was inactivated every 6.8 minutes in simulated saliva and every 14.3 minutes in culture media when exposed to simulated sunlight representative of the summer solstice at 40°N latitude at sea level on a clear day. Significant inactivation also occurred, albeit at a slower rate, under lower simulated sunlight levels. The present study provides the first evidence that sunlight may rapidly inactivate SARS-CoV-2 on surfaces, suggesting that persistence, and subsequently exposure risk, may vary significantly between indoor and outdoor environments. Additionally, these data indicate that natural sunlight may be effective as a disinfectant for contaminated nonporous materials.

Abstract. Szemerédi's regularity lemma is an important tool in graph theory which has applications throughout combinatorics.In this paper we prove an analogue of Szemerédi's regularity lemma in the context of abelian groups and use it to derive some results in additive number theory.One is a structure theorm for sets which are almost sum-free. If A ⊆ {1, . . . , N } has δN 2 triples (a 1 , a 2 , a 3 ) for which a 1 + a 2 = a 3 then A = B ∪ C, where B is sum-free and |C| = δ ′ N , and δ ′ → 0 as δ → 0Another answers a question of Bergelson, Host and Kra. If α, ǫ > 0, if N > N 0 (α, ǫ) and if A ⊆ {1, . . . , N } has size αN , then there is some d = 0 such that A contains at least (α 3 − ǫ)N three-term arithmetic progressions with common difference d.

Aerosols represent a potential transmission route of COVID-19. This study examined effect of simulated sunlight, relative humidity, and suspension matrix on stability of SARS-CoV-2 in aerosols. Simulated sunlight and matrix significantly affected decay rate of the virus. Relative humidity alone did not affect the decay rate; however, minor interactions between relative humidity and other factors were observed. Mean decay rates (± SD) in simulated saliva, under simulated sunlight levels representative of late winter/early fall and summer were 0.121 ± 0.017 min−1 (90% loss, 19 minutes) and 0.306 ± 0.097 min−1 (90% loss, 8 minutes), respectively. Mean decay rate without simulated sunlight across all relative humidity levels was 0.008 ± 0.011 min−1 (90% loss, 286 minutes). These results suggest that the potential for aerosol transmission of SARS-CoV-2 may be dependent on environmental conditions, particularly sunlight. These data may be useful to inform mitigation strategies to minimize the potential for aerosol transmission.