Children are unlikely to have been the primary source of household SARS-CoV-2 infections

Yanshan Zhu; Conor J Bloxham; Katina D Hulme; Jane E Sinclair; Zhen Wei Marcus Tong; Lauren E Steele; Ellesandra C Noye; Jiahai Lu; Keng Yih Chew; Janessa Pickering; Charles Gilks; Asha C Bowen; Kirsty R Short

Here, we analyse previously published literature from China, Singapore, South Korea, Japan, and Iran to show that children infected with SARS-CoV-2 displayed a broad range of clinical characteristics. Whilst some children developed severe disease, others presented asymptomatically with normal chest CT findings. These data are consistent with current consensus is that clinical symptoms of COVID-19 are, on average, milder in children (although severe infections can still occur). [4] [5] [6] [7] [8] Similarly findings have been made in children infected with either SARS or MERS. 9,10 At present, it remains unclear why children may develop less severe forms of COVID-19. It has been suggested that the receptor for SARS-CoV-2, ACE2, may be expressed at a lower level in children than in adults. 16 Alternatively, these observations may reflect the fact that the paediatric immune system is more adept than that of adults at dealing with infections for which there is no pre-existing immunity. 58, 59 This is reflected in the comparatively mild infections experienced by children upon infection with measles virus and varicella zoster virus. 60, 61 Understanding age-dependent differences in the pathogenesis of SARS-CoV-2 remains a key priority for future research.