Evidence before this study
As of August 4, 2020, our PubMed search using the keyword “COVID-19” OR “SARS-CoV-2” AND “secondary attack rate” obtained 17 articles in the estimated English language. Calculate the rate of secondary attacks in different groups. Of these studies, 11 (from Mainland China, Hong Kong, Taiwan, and South Korea) examined the rate of secondary attacks among community groups, while others were limited to Specific tight contact settings. Various community cohort studies analyzed 27 to 585 index cases and 106 to 4007 close contacts, and reported household attack rates ranging from 7.6% to 23%. No studies have examined serum rates. Three studies have identified independent exposure risk factors for coronavirus 2 (SARS-CoV-2) acute respiratory syndrome: staying in the same household and traveling in the same case. (a study in Shenzhen, China), over 18 years old and married to a case index (one study in Wuhan, China) and 60 years of age or older (a Guangzhou study , China).
The added value of this study
We used contact tracking data from 7770 close contacts (1863 family contacts, 2319 business contacts and 3588 social contacts) of the COVID-19 cases. Confirmed PCR was isolated for 2 weeks and referred to PCR testing if symptoms appear. In addition, a subset of 1150 close contacts (524 family contacts, 207 business contacts, and 419 social contacts) agreed to a serological test after quarantine was completed and assessed. with detailed symptom and risk factors questionnaires. Extensive contact tracking, careful follow-up of contacts during and after quarantine, and low community prevalence allows for the establishment of clear case contacts and case definition There are no strict symptoms. Using the Bayesian model, we estimate that the symptom-based PCR testing strategy missed more than half of the SARS-CoV-2 positive near exposures and more than one third of the close positive exposures to SARS-CoV-2 has no symptoms. Risk factor analysis identified longer verbal interactions and bedroom sharing as independent exposure risk factors for transmission of SARS-CoV-2 to close home contacts. family. For those not in close family contact, the exposure risk factors independently associated with SARS-CoV-2 transmission were time of verbal interactions, car sharing, and exposure to multiple schools. Consistent index longer. Among both household and non-household contacts, indirect contact, meal sharing and toilet sharing were not independently associated with SARS-CoV-2 transmission.
Implications of all evidence are available
Available findings, including those from our study, support physical distance and reduce verbal interactions as part of community measures to prevent SARS transmission. -CoV-2. In view of the significant asymptomatic infection rate, periodic examination of close contacts regardless of symptoms will reduce missed diagnoses. Close family contacts, those at high risk of transmission of SARS-CoV-2, should be given priority in routine testing. Detection of SARS-CoV-2 positive close household contacts will result in the person being displaced from the household or taking physical and infection prevention measures. other in the household.