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COVID-19 news from Annals of Internal Medicine

Embargoed news from Annals of Internal Medicine

American College of Physicians

Below please find a summary and link(s) of new coronavirus-related content published today in Annals of Internal Medicine. The summary below is not intended to substitute for the full article as a source of information. A collection of coronavirus-related content is free to the public at

Household contact the greatest risk for transmission of COVID-19
Asymptomatic patients less likely to infect close contacts compared to severe cases
Secondary transmission acquired from public transportation was rare

Researchers from Southern Medical University, Guangzhou, China traced more than 3,410 close contacts of 391 COVID-19 index cases between January and March 2020 to evaluate the risk for disease transmission in different settings. They found that risk for secondary transmission of COVID-19 was less than 4 percent among close contacts of persons with COVID-19. In addition, secondary infections acquired while using public transportation were rare. In contrast, 1 in 10 household contacts was found to be infected.

The researchers also found that patients with more clinically severe disease were more likely to infect their close contacts than were less severe index cases. Those with asymptomatic cases were the least likely to infect their close contacts. Manifestation of certain symptoms, such as expectoration, in index cases was also associated with an increased risk for infection in their close contacts. Read the full text:


Media contacts: A PDF of this paper is not yet available. Please click the link to read full text. Lead authors, Chen Mao, PhD, can be reached at and Jinling Tang, PhD can be reached at

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