Epidemiological Characteristics of COVID-19 Close Contacts in Ningbo City

COVID-19: Epidemiological Characteristics of COVID-19 Close Contacts in Ningbo City. Spencer EA, Heneghan C


Published on June 30, 2020

Reference Chen Y, Wang AH, Yi B, et al. Zhonghua Liu Xing Bing Xue Za Zhi. Epidemiological Characteristics of Infection in COVID-19 Close Contacts in Ningbo City 2020; 41(5):667-671. 2018
Study type
Country China
Setting Community and hospital
Funding Details Non reported
Transmission mode Community, close contacts, and superspreading
Exposures Households, Hospitals, Travel, Mass Gatherings

Bottom Line

Transmission rates varied by closeness of contact and by type of contact. A single case travelling on a bus and attending a mass gathering appeared to be responsible for infecting 25 individuals

Evidence Summary

157 local reported confirmed cases and 30 asymptomatic infected persons were determined to have 2,147 close contacts that had 132 local infections, (110 confirmed cases, and 22 asymptomatic infections).

 Infection rates:

  • Close contacts of confirmed cases 6.2% (132/2,147).
  • Close contacts of asymptomatic infections 4.1% (6/146)

Infection rate varied by contact type: 

  • Friends/travellers (22.3%), 
  • Family members (18.0%), 
  • Relatives (4.7%). 

There were no infections among medical staff close contacts. Living with the case (13.3%), taking the same transportation (11.9%), and dining together (7.2%) were high risk factors for infection. Cross-infection in the hospital was significant (1.9%). 

From the study of a “superspreader” case who attended a mass gathering: there were 68 close contacts, 23 were diagnosed with new coronavirus pneumonia, and 2 were asymptomatic infections, with an infection rate of 37% (25/68).

What did they do?

The study was set up to investigate and collect the epidemiological investigation report information of all confirmed cases of new coronavirus pneumonia and asymptomatic infected persons reported by Ningbo City from 21st January to 6th March 2020, and confirm and track all close contacts of infected persons. The infection rate of close contacts under different exposures was investigated. 

This article also includes a report of a “superspreader” in which an infected female travelled by air-conditioned bus to a religious/community gathering and appeared to have spread the infection to several people on the bus and at the gathering. 

Study reliability

This is one observational study and it is hard to know whether the situation is representative of elsewhere

Clearly defined setting Demographic characteristics described Follow-up length was sufficient Transmission outcomes assessed Main biases are taken into consideration
Unclear Yes Yes Yes Unclear

What else should I consider?

It is not clear how the study of the superspreader fits with the main study, or if it is a separate study. The full text article is in Chinese and we used google automatic translator for the translation.

About the authors

Carl Heneghan

Carl is Professor of EBM & Director of CEBM at the University of Oxford. He is also a GP and tweets @carlheneghan. He has an active interest in discovering the truth behind health research findings

Elizabeth Spencer

Dr Elizabeth Spencer; MMedSci, PhD. Epidemiologist, Nuffield Department for Primary Care Health Sciences, University of Oxford.