Progression of COVID-19 under the highly restrictive measures imposed in Argentina.

The variety and extent of non-pharmaceutical measures implemented by the government to control COVID-19 in Argentina were exceptional, making this country the best example to analyze the evolution of COVID-19 under the most stringent and longer-lasting restrictive policies- which included 119 days of strict nation-wide lock-down, 304 days of less restrictive lock-downs, and 35 days of curfews. Two of the three peaks of infection correlated with the germicidal solar flux received in Argentina, suggesting a seasonal component and a role for the virus persisting in the environment. A massive public gathering crowding the presidential square in Buenos Aires, during which nearly half of those present were without face masks, did not alter the infection curve in that city.

Estimated Inactivation of Coronaviruses by Solar Radiation With Special Reference to COVID-19.

Using a model developed for estimating solar inactivation of viruses of biodefense concerns, we calculated the expected inactivation of SARS-CoV-2 virus, cause of COVID-19 pandemic, by artificial UVC and by solar ultraviolet radiation in several cities of the world during different times of the year. The UV sensitivity estimated here for SARS-CoV-2 is compared with those reported for other ssRNA viruses, including influenza A virus. The results indicate that SARS-CoV-2 aerosolized from infected patients and deposited on surfaces could remain infectious outdoors for considerable time during the winter in many temperate-zone cities, with continued risk for re-aerosolization and human infection.

Evaluation criteria for bioaerosol samplers.

Humans contract a variety of serious diseases through inhalation of infectious aerosols. Thus, the importance of monitoring air for microbial, toxic, or allergic content is recognized in clinical, occupational, and biodefense arenas. However, accurate monitoring of potentially contaminated environments can be hampered by selection of aerosol samplers with inadequate performance for the intended task.

Regression model for estimating inactivation of microbial aerosols by solar radiation.

The inactivation of pathogenic aerosols by solar radiation is relevant to public health and biodefense. We investigated whether a relatively simple method to calculate solar diffuse and total irradiances could be developed and used in environmental photobiology estimations instead of complex atmospheric radiative transfer computer programs. The second-order regression model that we developed reproduced 13 radiation quantities calculated for equinoxes and solstices at 35(°) latitude with a computer-intensive and rather complex atmospheric radiative transfer program (MODTRAN) with a mean error <6% (2% for most radiation quantities).

Inactivation of Pseudomonas aeruginosa by direct sunlight.

We determined the sensitivity of Pseudomonas aeruginosa to direct sunlight radiation, while maintaining the experimental temperature below levels harmful to the bacterium. The results presented here were similar to previous data on solar sensitivity obtained half a world away on another related bacterial species. The findings presented in this study suggest that related bacteria have a characteristic sensitivity to sunlight with their survival depending mainly on the fluence (photons) received in a dose-dependent manner that is otherwise relatively independent from latitude, atmospheric ozone and other local conditions.