Test-to-Stay After Exposure to SARS-CoV-2 in K-12 Schools

OBJECTIVES: We evaluated the safety and efficacy of a test-to-stay program for unvaccinated students and staff who experienced an unmasked, in-school exposure to someone with confirmed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Serial testing instead of quarantine was offered to asymptomatic contacts. We measured secondary and tertiary transmission rates within participating schools and in-school days preserved for participants. METHODS: Participating staff or students from universally masked districts in North Carolina underwent rapid antigen testing at set intervals up to 7 days after known exposure. Collected data included location or setting of exposure, participant symptoms, and school absences up to 14 days after enrollment. Outcomes included tertiary transmission, secondary transmission, and school days saved among test-to-stay participants. A prespecified interim safety analysis occurred after 1 month of enrollment. RESULTS: We enrolled 367 participants and completed 14-day follow-up on all participants for this analysis. Nearly all (215 of 238, 90%) exposure encounters involved an unmasked index case and an unmasked close contact, with most (353 of 366, 96%) occurring indoors, during lunch (137 of 357, 39%) or athletics (45 of 357, 13%). Secondary attack rate was 1.7% (95% confidence interval: 0.6%-4.7%) based on 883 SARS-CoV-2 serial rapid antigen tests with results from 357 participants; no tertiary cases were identified, and 1628 (92%) school days were saved through test-to-stay program implementation out of 1764 days potentially missed. CONCLUSION: After unmasked in-school exposure to SARS-CoV-2, even in a mostly unvaccinated population, a test-to-stay strategy is a safe alternative to quarantine

TOI-269 b: An eccentric sub-Neptune transiting a M2 dwarf revisited with ExTrA

We present the confirmation of a new sub-Neptune close to the transition between super-Earths and sub-Neptunes transiting the M2 dwarf TOI-269 (TIC 220 479 565, V = 14.4 mag, J = 10.9 mag, Ro = 0.40 Ro, Mo = 0.39 Mo, d = 57 pc). The exoplanet candidate has been identified in multiple TESS sectors, and validated with high-precision spectroscopy from HARPS and ground-based photometric follow-up from ExTrA and LCO-CTIO. We determined mass, radius, and bulk density of the exoplanet by jointly modeling both photometry and radial velocities with juliet. The transiting exoplanet has an orbital period of P = 3.6977104 ± 0.0000037 days, a radius of 2.77 ± 0.12 R·, and a mass of 8.8 ± 1.4 M·. Since TOI-269 b lies among the best targets of its category for atmospheric characterization, it would be interesting to probe the atmosphere of this exoplanet with transmission spectroscopy in order to compare it to other sub-Neptunes. With an eccentricity e = 0.425-0.086+0.082, TOI-269 b has one of the highest eccentricities of the exoplanets with periods less than 10 days. The star being likely a few Gyr old, this system does not appear to be dynamically young. We surmise TOI-269 b may have acquired its high eccentricity as it migrated inward through planet-planet interactions

Influence of binder type on leaching rate and ingestion of microbound diets by mud crab, Scylla serrata (Forsskål), larvae

Microbound diets (MBD), composed of nutrients held within a matrix or binder, were shown to be readily ingested by larvae of the mud crab, Scylla serrata (Forsskål). In an effort to improve experimental MBD developed for S. serrata larvae, this study determined the effects of various binders on estimated larval ingestion of MBD as well as their leaching rates. Microbound diets with the same dietary compositions were bound with either agar, alginate, carrageenan, gelatin or zein. All diets contained 14C-labelled rotifers and were fed to Zoea I, III, V larvae and megalopae. The 14C content of larvae fed 14C-labelled MBD for 2 h was used to estimate the relative ingestion rates of MBD. For all larval stages tested, the estimated mean larval ingestion of MBD did not differ significantly between binder types (P>0.05). Determination of the amount of 14C-labelled nutrient leaching from MBD bound with various binders after 30, 60 and 240 min of immersion showed that for all types of binders, 14C leaching occurred primarily within the first 30 min of immersion. Zein-bound MBD consistently showed the lowest numerical leaching rate among the five binders tested for all immersion periods examined, and the differences compared with other binders were often significant, particularly after 60 and 240 min of immersion. Larval feeding experiments showed that MBD prepared with binders showing higher rates of leaching were not utilized to a greater degree by S. serrata larvae. Furthermore, unnecessary leaching from MBD particles wastes dietary nutrients and is likely to impact on water quality. On this basis, our results suggest that because of its consistently lower leaching rates, zein is probably a more suitable binder for MBD developed for S. serrata larvae