Fauci: 'About 40%-45% of Infections Are Asymptomatic'

Marcia Frellick

September 11, 2020

Editor's note: Find the latest COVID-19 news and guidance in Medscape's Coronavirus Resource Center.

Anthony Fauci, MD, highlighting the latest COVID-19 developments on Friday, said, "It is now clear that about 40%-45% of infections are asymptomatic."

Dr Anthony Fauci (The Associated Press)

Asymptomatic carriers can account for a large proportion — up to 50% — of virus transmissions, Fauci, director of the National Institute of Allergy and Infectious Diseases, told a virtual crowd of critical care clinicians gathered by the Society of Critical Care Medicine (SCCM).

Such transmissions have made response strategies, such as contact tracing, extremely difficult, he said.

Lew Kaplan, MD, president of SCCM, told Medscape Medical News after the presentation, "That really supports the universal wearing of masks and the capstone message from that — you should protect one another.

"That kind of social responsibility that sits within the public health domain to me is as important as the vaccine candidates and the science behind the receptors. It underpins the necessary relationship and the interdependence of the medical community with the public," Kaplan added.

Fauci's plenary led the SCCM's conference, "COVID-19: What's Next/Preparing for the Second Wave," running today and Saturday.

Why US Response Lags Behind Spain and Italy

"This virus has literally exploded upon the planet in a pandemic manner which is unparalleled to anything we've seen in the last 102 years since the pandemic of 1918," Fauci said.

“Unfortunately, the United States has been hit harder than any other country in the world, with 6 million reported cases."

He explained that in the European Union countries the disease spiked early on and returned to a low baseline. "Unfortunately for them," Fauci said, "as they're trying to open up their economy, it’s coming back up.”

The United States, he explained, plateaued at about 20,000 cases a day, then a surge of cases in Florida, California, Texas, and Arizona brought the cases to 70,000 a day. Now cases have returned to 35,000 to 40,000 a day.

The difference in the trajectory of the response, he said, is that compared with Spain and Italy, for example, the United States has not shut down mobility in parks, outdoor spaces, and grocery stores nearly as much as some European countries did.

He pointed to numerous clusters of cases, spread from social or work gatherings, including the well-known Skagit County Washington state choir practice in March, in which a symptomatic choir member infected 87% of the 61 people rehearsing.

Vaccine by End of the Year

As for a vaccine timeline, Fauci told SCCM members, "We project that by the end of this year, namely November/December, we will know if we have a safe and effective vaccine and we are cautiously optimistic that we will be successful, based on promising data in the animal model as well as good immunological data that we see from the phase 1 and phase 2 trials."

However, also on Friday, Fauci told MSNBC's Andrea Mitchell that a sense of normalcy is not likely before the middle of next year.

"By the time you mobilize the distribution of the vaccinations, and you get the majority, or more, of the population vaccinated and protected, that's likely not going to happen [until] the mid- or end of 2021," he said.

According to the Centers for Disease Control and Prevention (CDC) case tracker, as of Thursday, COVID-19 had resulted in more than 190,000 deaths overall and more than 256,000 new cases in the United States in the past 7 days.

Fauci has warned that the next few months will be critical in the virus' trajectory, with the double onslaught of COVID-19 and the flu season.

On Thursday, Fauci said, "We need to hunker down and get through this fall and winter because it's not going to be easy."

Fauci remains a top trusted source in COVID-19 information, poll numbers show.

A Kaiser Family Foundation poll released Thursday found that 68% of US adults had a fair amount or a great deal of trust that Fauci would provide reliable information on COVID-19, just slightly more that the 67% who said they trust the CDC information. About half (53%) say they trust Deborah Birx, MD, the coordinator for the White House Coronavirus Task Force, as a reliable source of information.

The poll also found that 54% of Americans said they would not get a COVID-19 vaccine if one was approved by the US Food and Drug Administration before the November election and was made available and free to all who wanted it.

Kaplan and Fauci report no relevant financial relationships.

COVID-19: What’s Next/Preparing for the Second Wave. Presented September 11, 2020.

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