CDC estimates that 35% of coronavirus infections are asymptomatic 

The US Centers for Disease Control and Prevention posted new guidance on its website that estimates that about a third of coronavirus infections are asymptomatic.

The agency also says its “best estimate” is that 0.4% of people who show symptoms and have Covid-19 will die, and it estimates that 40% of coronavirus transmission is occurring before people feel sick.

In the guidance, intended for modelers and public health officials, the CDC outlines five potential scenarios. Four represent “the lower and upper bounds of disease severity and viral transmissibility.” The fifth is the CDC’s “current best estimate about viral transmission and disease severity in the United States.”

In that scenario, the agency describes its estimate that 0.4% of people who feel sick with Covid-19 will die. For people age 65 and older, the CDC puts that number at 1.3%. For people 49 and under, the agency says 0.05% of symptomatic people will die. It assumes that people without symptoms are every bit as infectious as those with symptoms.

The agency also estimates that 3.4% of symptomatic people with Covid-19 will require hospitalization, with that number rising to 7.4% in people 65 and older.

In the most severe scenario, the CDC assumes that 1% of people overall with Covid-19 and symptoms will die. In the least severe scenario, the CDC puts that number at 0.2%.

“The scenarios are intended to advance public health preparedness and planning. They are not predictions or estimates of the expected impact of COVID-19,” the CDC says.

The agency also notes that its numbers could change as more is learned about Covid-19, and says they do not “reflect the impact of any behavioral changes, social distancing, or other interventions.” That would be relevant for some of the agency’s estimates, such as how many infections stem from each case.

With those caveats, the CDC said the new numbers are based on real data received before April 29. The CDC characterized them as preliminary estimates from federal agencies, including the CDC and the HHS Office of the Assistant Secretary for Preparedness and Response.