When Is a Individual With COVID-19 Most Infectious?

By Robert Preidt

HealthDay Reporter

FRIDAY, Aug. 27, 2021 (HealthDay Information) — New analysis delivers a solution to a burning query: When are COVID-19 sufferers most infectious?

The reply? Two days earlier than and three days after they develop signs.

The findings spotlight the significance of speedy testing and quarantine if somebody is feeling sick, the research authors mentioned.

The researchers additionally discovered that contaminated persons are extra more likely to be asymptomatic in the event that they caught the virus from a major case (the primary contaminated particular person in an outbreak) who was additionally asymptomatic.

"In earlier research, viral load has been used as an oblique measure of transmission," mentioned research co-leader Dr. Leonardo Martinez, an assistant professor of epidemiology at Boston College's College of Public Well being.

"We needed to see if outcomes from these previous research, which present that COVID instances are most transmissible a couple of days earlier than and after symptom onset, could possibly be confirmed by taking a look at secondary instances amongst shut contacts," Martinez mentioned in a college information launch.

For the research, Martinez and his colleagues analyzed knowledge from about 9,000 shut contacts of major instances within the Zhejiang province of China from January 2020 to August 2020. That's earlier than the appearance of the much more contagious Delta variant.

Shut contacts included individuals who lived in the identical family or who dined collectively, co-workers, individuals in hospital settings and riders in shared autos. They have been monitored for a minimum of 90 days after their preliminary constructive COVID-19 take a look at outcomes.

Of the first instances, 89% developed delicate or average signs, 11% have been asymptomatic, and none had extreme signs.

Family contacts of major instances and individuals who have been uncovered to major instances a number of instances or for longer quantities of time had greater an infection charges than different shut contacts, the findings confirmed.

However all shut contacts have been extra more likely to be contaminated by the first case in the event that they have been uncovered shortly earlier than or after that particular person developed signs, in line with the research printed on-line Aug. 23 in JAMA Internal Medicine.

Compared to delicate and average symptomatic major instances, those that have been asymptomatic have been a lot much less more likely to infect shut contacts. In the event that they did, the contacts have been additionally much less more likely to have noticeable signs, the researchers reported.


"Our outcomes recommend that the timing of publicity relative to primary-case signs is essential for transmission, and this understanding gives additional proof that speedy testing and quarantine after somebody is feeling sick is a crucial step to regulate the epidemic," Martinez mentioned. "This research additional emphasizes the necessity for vaccination, which reduces scientific severity amongst those who develop COVID."

Extra info

The U.S. Facilities for Illness Management and Prevention has extra on COVID-19.

SOURCE: Boston College College of Medication, information launch, Aug. 26, 2021

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