Asymptomatic Covid-19 cases least likely to infect their close contacts: Study

Mumbai | Updated on August 15, 2020

According to a study published in the journal of Annals of Internal Medicine, household contact was the main setting for transmission of SARS-CoV-2, and the risk for transmission of SARS-CoV-2 among close contacts increased with the severity of index cases.

The authors of the study examined settings of Covid-19 transmission in a cohort study of 3410 close contacts of 391index cases of Covid-19 in Guangzhou, China.

"We wanted to evaluate the risk for transmission of SARS-CoV-2 to close contacts of persons infected with Covid-19 in Guangzhou region," said study researchers from Southern Medical University in China.

The study was then classified into 5 subcategories: household, public transportation, health care settings, entertainment venues or workplaces, and multiple settings. “Multiple settings” indicates exposure in more than 1 contact setting.

Study findings

The study found that the secondary attack rate was less than 4 per cent among close contacts of persons with Covid-19.

Secondary infections acquired while using public transportation or venturing out in public were rare. In contrast, 1 in 10 household contacts was found to be infected.

The authors noted: “We found that patients with more clinically severe disease were more likely to infect their close contacts than were less severe index cases.”

They added that asymptomatic cases were least likely to infect their close contacts.

The authors mentioned that the manifestation of certain symptoms, including expectoration, in index cases was also associated with an increased risk for infection in their close contacts.

The authors believe the spread of the virus is rampant in household settings also because mask-wearing was mandatory in public settings but not in households during the study period.

Thus, effective measures to reduce household transmission and quarantine of household contacts are extremely important, the authors added.

Published on August 15, 2020

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