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COVID-19 Transmission Dynamics Among Close Contacts of Index Patients With COVID-19: A Population-Based Cohort Study in Zhejiang Province, China.
Ge, Yang; Martinez, Leonardo; Sun, Shengzhi; Chen, Zhiping; Zhang, Feng; Li, Fangyu; Sun, Wanwan; Chen, Enfu; Pan, Jinren; Li, Changwei; Sun, Jimin; Handel, Andreas; Ling, Feng; Shen, Ye.
  • Ge Y; Department of Epidemiology and Biostatistics, College of Public Health, University of Georgia, Athens.
  • Martinez L; Department of Epidemiology, School of Public Health, Boston University, Boston, Massachusetts.
  • Sun S; Department of Environmental Health, School of Public Health, Boston University, Boston, Massachusetts.
  • Chen Z; Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, China.
  • Zhang F; Department of Biostatistics and Data Science, School of Public Health, University of Texas Health Science Center at Houston, Houston.
  • Li F; Department of Epidemiology, Human Genetics and Environmental Sciences, School of Public Health, University of Texas Health Science Center at Houston, Houston.
  • Sun W; Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, China.
  • Chen E; Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, China.
  • Pan J; Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, China.
  • Li C; Department of Epidemiology, Tulane University School of Public Health and Tropical Medicine, New Orleans, Louisiana.
  • Sun J; Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, China.
  • Handel A; Department of Epidemiology and Biostatistics, College of Public Health, University of Georgia, Athens.
  • Ling F; Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, China.
  • Shen Y; Department of Epidemiology and Biostatistics, College of Public Health, University of Georgia, Athens.
JAMA Intern Med ; 181(10): 1343-1350, 2021 10 01.
Article in English | MEDLINE | ID: covidwho-1368408
ABSTRACT
Importance Much remains unknown about the transmission dynamics of COVID-19. How the severity of the index case and timing of exposure is associated with disease in close contacts of index patients with COVID-19 and clinical presentation in those developing disease is not well elucidated.

Objectives:

To investigate the association between the timing of exposure and development of disease among close contacts of index patients with COVID-19 and to evaluate whether the severity of the index case is associated with clinical presentation in close contacts who develop COVID-19. Design, Setting, and

Participants:

This study used a large, population-based cohort of 730 individuals (index patients) who received a diagnosis of COVID-19 in Zhejiang Province, China, from January 8 to July 30, 2020, along with a contact tracing surveillance program. Field workers visited 8852 close contacts of the index patients and evaluated them for COVID-19 through August 2020. A timeline was constructed to characterize different exposure periods between index patients and their contacts. Main Outcomes and

Measures:

The primary outcome was the attack rate of COVID-19, defined as the total number of new COVID-19 cases diagnosed among contacts of index patients divided by the total number of exposed contacts. A secondary outcome was asymptomatic clinical presentation among infected contacts. Relative risks were calculated to investigate risk factors for COVID-19 among contacts and asymptomatic clinical presentation among infected contacts.

Results:

Among 8852 close contacts (4679 male contacts [52.9%]; median age, 41 years [interquartile range, 28-54 years]) of 730 index patients (374 male patients [51.2%]; median age, 46 years [interquartile range, 36-56 years]), contacts were at highest risk of COVID-19 if they were exposed between 2 days before and 3 days after the index patient's symptom onset, peaking at day 0 (adjusted relative risk [ARR], 1.3; 95% CI, 1.2-1.5). Compared with being exposed to an asymptomatic index patient, the risk of COVID-19 among contacts was higher when they were exposed to index patients with mild (ARR, 4.0; 95% CI, 1.8-9.1) and moderate (ARR, 4.3; 95% CI, 1.9-9.7) cases of COVID-19. As index case severity increased, infected contacts were less likely to be asymptomatic (exposed to patient with mild COVID-19 ARR, 0.3; 95% CI, 0.1-0.9; exposed to patient with moderate COVID-19 ARR, 0.3; 95% CI, 0.1-0.8). Conclusions and Relevance This cohort study found that individuals with COVID-19 were most infectious a few days before and after symptom onset. Infected contacts of asymptomatic index patients were less likely to present with COVID-19 symptoms, suggesting that quantity of exposure may be associated with clinical presentation in close contacts.
Subject(s)

Full text: Available Collection: International databases Database: MEDLINE Main subject: Contact Tracing / SARS-CoV-2 / COVID-19 Type of study: Diagnostic study / Etiology study / Incidence study / Observational study / Risk factors Limits: Adult / Aged / Female / Humans / Male / Middle aged / Young adult Country/Region as subject: Asia Language: English Journal: JAMA Intern Med Year: 2021 Document Type: Article

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Full text: Available Collection: International databases Database: MEDLINE Main subject: Contact Tracing / SARS-CoV-2 / COVID-19 Type of study: Diagnostic study / Etiology study / Incidence study / Observational study / Risk factors Limits: Adult / Aged / Female / Humans / Male / Middle aged / Young adult Country/Region as subject: Asia Language: English Journal: JAMA Intern Med Year: 2021 Document Type: Article