Most COVID-19 transmission comes from people who don’t have symptoms

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A new study published in JAMA estimates that transmission of COVID-19 from asymptomatic individuals accounts for more than half of all transmissions.

The decision analytical model used assumed that 30% of individuals infected with COVID-19 never develop symptoms and are 75% as infectious as those who do. These baseline assumptions imply that those who never show symptoms may account for about 24% of all transmission. The study estimated that 59% of all transmission came from asymptomatic transmission — 35% from presymptomatic individuals and 24% from individuals who never develop symptoms.

“In this decision analytical model of multiple scenarios of proportions of asymptomatic individuals with COVID-19 and infectious periods, transmission from asymptomatic individuals was estimated to account for more than half of all transmissions,” according to the study. “In addition to identification and isolation of persons with symptomatic COVID-19, effective control of spread will require reducing the risk of transmission from people with infection who do not have symptoms. These findings suggest that measures such as wearing masks, hand hygiene, social distancing, and strategic testing of people who are not ill will be foundational to slowing the spread of COVID-19 until safe and effective vaccines are available and widely used.”

HEALTH STAT

To avoid listeria and other foodborne bacterial illnesses, the CDC recommends keeping factory-sealed, unopened packages of deli meats in the refrigerator for no longer than 2 weeks, and keeping opened packages and meat sliced at a local deli in the refrigerator for no longer than 3 to 5 days.