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A paper, published in The Lancet Infectious Diseases, reports on contact tracing and isolation and SARS-CoV-2 coronavirus spread in in Shenzhen, China.
Dr Simon Clarke, Associate Professor in Cellular Microbiology, University of Reading, said:
“We know that children are much less likely than adults to get a serious disease, but is that because they don’t get infected by the virus causing CoViD19 so easily? This research from Shenzhen answers that important question, reporting that children do indeed get infected just as frequently as adults. As children are carriers, re-opening schools could expose parents, grandparents and teachers to infection and in turn anyone they might come into contact with, pushing up R and risking a second wave.
“Previous studies had been based on testing people with symptoms, but this one identifies infected individuals by contact tracing. The researchers observed that transmission most frequently occurred between members of the same household but that age had no effect on the likelihood of infection. However, children were observed to have lower incidences of severe symptoms, confirming existing opinions.”
Dr Tom Wingfield, Senior Clinical Lecturer and Honorary Consultant Physician, Liverpool School of Tropical Medicine, said:
“Bi et al’s article reports on the transmission and clinical features of SARS-CoV-2, the coronavirus that causes Covid-19 illness, in the megacity of Shenzen in South East China. Specifically, it compares these features between people who were tested because they showed symptoms versus those who were tested through contact tracing. Although the findings may not be generalizable because they refer to a single region of China during an early phase of the Chinese epidemic when there was heightened surveillance and isolation, there are important points from this study for the UK and other countries to reflect on.
“First, tracing and testing of close contacts showed that contacts living in the same household and having frequent contact with someone with SARS-CoV-2 were the most likely to become infected. This indicates that contact tracing in households in which one member is diagnosed with Covid-19 is likely to be high yield and potentially cost-effective.
“Second, tracing and testing reduced the time between individuals showing symptoms of Covid-19 to isolating themselves. This suggests that contact tracing may be a valuable strategy to reduce transmission rates, especially in the community.
“Third, one in five close contacts who tested positive for SARS-CoV-2 positive had no symptoms and one in three had no fever. This adds to existing evidence that a significant proportion of people with SARS-CoV-2 appear to have no – or no noticeable – symptoms. It is important that this is taken into account by countries designing community tracing and testing strategies, particularly if such strategies will only focus on contacts with symptoms.
“Fourth, children were shown to have the same risk of SARS-CoV-2 as the background population but rarely developed severe Covid-19 symptoms. This is of relevance when considering the impact of lifting of lockdown measures, including opening schools, on community transmission rates of SARS-CoV-2.
“Finally, Bi et al’s findings contribute to our growing understanding of the period of time to recovery from Covid-19. Their results show that time to recovery from Covid-19 can be prolonged over some weeks, especially in older people and those with more severe disease. For those recovering from Covid-19, ability to carry out standard day-to-day activities, return to work duties, and the potential need for additional social care should all be considered.”
‘Epidemiology and transmission of COVID-19 in 391 cases and 1286 of their close contacts in Shenzhen, China: a retrospective cohort study’ by Qifang Bi et al. was published in The Lancet Infectious Diseases on Monday 27 April 2020.
DOI: 10.1016/S1473-3099(20)30287-5
https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(20)30287-5/fulltext
Declared interests
None received.