S evere acute respiratory syndrome coronavirus (SARS-CoV) 2, is a readily transmissible zoonotic pathogen and the etiologic agent of the coronavirus disease (COVID-19) pandemic (1). To determine aerosol stability of the virus, we measured the dynamic (short-term) aerosol efficiencies of SARS-CoV-2 and compared its efficiency with those of SARS-CoV and Middle East respiratory syndrome coronavirus (MERS-CoV). The Study We analyzed these 3 viruses' dynamic aerosol efficiencies using 3 nebulizers, the Collison 3-jet (C3), Collison 6-jet (C6) (http://www.chtechusa.com), and Aerogen Solo (AS) (https://www.aerogen.com), to generate viral aerosols (Appendix, https://wwwnc. cdc.gov/EID/article/26/9/20-1806-App1.pdf). We performed comparative efficiency experiments once in each of 4 aerobiology laboratories (Tulane Uni

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The emergent coronavirus, designated severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), is a zoonotic pathogen that has demonstrated remarkable transmissibility in the human population and is the etiological agent of a current global pandemic called COVID-19. We measured the dynamic (short-term) aerosol efficiencies of SARS-CoV-2 and compared the efficiencies with two other emerging coronaviruses, SARS-CoV (emerged in 2002) and Middle Eastern respiratory syndrome CoV (MERS-CoV; emerged starting in 2012). We also quantified the long-term persistence of SARS-CoV-2 and its ability to maintain infectivity when suspended in aerosols for up to 16 hours.

Disease-resistance genes introduced into cultivated plants are often rendered ineffective by the ability of pathogen populations to overcome host resistance. The bacterial pathogen Xanthomonas campestris pathovar vesicatoria causes bacterial spot disease of tomato and pepper, and this pathogen has been shown to overcome disease resistance in pepper (Capsicum annuum) by evading the recognition and defence response of the host plant. Numerous resistance genes to bacterial spot have been identified in pepper and its wild relatives, each providing resistance to specific races of X.c. vesicatoria. The resistance gene Bs1, for example, provides resistance to X.c. vesicatoria strains expressing the avirulence gene avrBs1; Bs2 provides resistance to stains expressing avrBs2 and so on. We now report that avr Bs2 is highly conserved among strains of X.c. vesicatoria, and among many other pathovars of X. campestris. Furthermore, we find that avrBs2 is in fact needed for full virulence of the pathogen on susceptible hosts. This implies that plants carrying Bs2 can recognize an essential gene of the bacterial pathogen, which may explain why Bs2 confers the only effective field resistance to X.c. vesicatoria in pepper.