No abstract

Medical Research Council and the Wellcome Trust.

Using data from 4678 children participating in VirusWatch, a UK household cohort study, we estimated the prevalence of persistent symptoms as 1.7%, and 4.6% in children with a history of SARS-CoV-2 infection. Persistent symptoms prevalence was higher in girls, teenagers and children with long-term conditions.

In winter 2008, kindergartens and primary schools in Hong Kong were closed for 2 weeks after media coverage indicated that 3 children had died, apparently from infl uenza. We examined prospective infl uenza surveillance data before, during, and after the closure. We did not fi nd a substantial effect on community transmission.H ong Kong, Special Administrative Region, People's Republic of China, is a subtropical city in Southeast Asia at the epicenter of global infl uenza activity (1). Epidemiologically, infl uenza usually displays biannual seasonality, consisting of a winter peak typically between January and March and a summer peak in June and July, often with an elevated plateau in April and May between the winter and summer peaks (2-4).On the evening of March 12, 2008, after 3 children had died, apparently from infl uenza, the government of Hong Kong announced that all primary schools, special schools, kindergartens, and day nurseries would close the following day for a total of 2 weeks, 1 week earlier than the scheduled start of the annual week-long Easter break (5,6). The StudyWe reviewed prospective surveillance data on infl uenza and infl uenza-like illness activity during the 2008 winter infl uenza season. We then considered the effects of the school closures on community transmission.As Surveillance data from different settings before, during, and after the period of school closures are shown in the Figure. Laboratory isolation of infl uenza viruses in children (panel A) and adults (panel B) show that the infl uenza season began in January, rose to a peak in late February, and was already waning by the time the decision was made to close schools, as temperatures and relative humidity were increasing (8). Infl uenza circulation has remained at a low baseline level since schools reopened in early April. Absenteeism rates in sentinel childcare centers and primary schools gradually rose to maximums of 7.9% and 3.5%, respectively, before the school closures and returned to low levels after the closures (data not shown). Similarly, infl uenza consultation rates at public and private outpatient clinics (panel C) peaked before the closures and generally refl ected the reference laboratory data, except for a dip during Chinese New Year, when many sentinel practices were closed.When compared with the infl uenza seasons of the preceding 9 years, the 2008 winter infl uenza season was moderately severe in terms of outpatient consultations (online Appendix Figure, available from www.cdc.gov/ EID/content/14/10/1660-appF.htm). Infl uenza hospital admission rates in children <4 years reached peak levels of 30/100,000 population in 2006 and 41/100,000 in 2007, both mild seasons. These rates were similar to the peak level of 39/100,000 in 2008 (Figure, panel D) (6). The elderly appeared to have been less affected, with no clear rate increases noted by febrile sentinel surveillance in elderly care homes and generally low infl uenza-related admission rates in this age group (data not shown).Panel E of the Figure shows dai...

Previous studies of alveolarization have used rats or lambs; however, neither closely reflects human alveolar development. We characterized alveolar development in rabbits (n = 3-7 /group) at 28 days gestation (dg) to 9 mo to determine whether they followed the human pattern more closely. The right lung was made up of 30% alveolar and 50% duct space at 28 dg to 3 days and of 50 and 30%, respectively, at 14 days to 9 mo. Tissue fraction and alveolar wall thickness decreased by 40% 28 dg to birth. At birth, approximately 4.5% of the number of alveoli seen at 9 mo were present, with alveolar number increasing progressively well into adulthood. The rate of alveolar formation was high around birth, decreasing progressively with age. Alveolar volume increased more than twofold (28 dg to birth) and continued to increase postnatally to 16 wk. Surface fraction decreased by 17% (28 dg to 3 days), after which it remained uniform. Our findings suggest that the timing of onset of alveolarization in humans and rabbits is similar and that rabbits may be used to model postnatal influences on alveolar development.