The impetus for this came from Elizabeth Cohen, senior medical correspondent for CNN, which at least to me seems like fantastic investigative reporting.

Reasons to take this seriously if one still requires them. In brief:

  • Evidence of high levels of viral “shedding” --and from the upper respiratory tract as opposed to the lower-- within the earliest days of infection, said to be “1,000 times greater” than was seen with 2002-03 Sars outbreak
  • Indications that asymptomatic infection more contagious than symptomatic infection (viral shedding believed to begin to drop after around Day 5 of infection in80% or so of those infected)
  • It is impossible to predict, at least right now, who will advance to the “cytokine storm”/hyperinflammatory phase which is increasingly difficult to manage as hospitals become burdened beyond capacity
  • New reports of “silent spreaders:” infected and contagious persons who never develop symptoms

Maybe others have stitched these pieces together in other places, but I have not seen it. Cohen cites several small write-ups of early detective work-- in Frankfurt, in Singapore, in Taipin, and even extrapolating from growing Massachusetts cluster-- that appear to suggest not only that people without symptoms are unknowingly propagating the spread, but that they might even be more infectious than those showing symptoms.

At least to my simple mind, this seems to raise important (if not huge) issues around the availability of testing* (on which the New Yorker published an exhaustive account yesterday) or, failing that (since just about no one can get tested in this friggin’ dysfunctional country) our misplaced sense of security (or at least mine) in how we interact with others-- especially those who might be at heightened risk for serious outcomes.

Of note and possible interest or importance, the much talked about Imperial College modeling that appears to have swayed both BJ and DJ into changing course with their approaches to (or in the case of the US, the mere acknowledgement of, really) the epidemic assumes that symptomatic individuals are more infectious (1.5X more so) than asymptomatic individuals. I wish someone would ask them to re-run their numbers with the opposite assumption.

[More recently, the CDC released a statement indicating that 46% of the infected Diamond Princess passengers and crew were asymptomatic at the time of testing positive-- and that 18% of infected persons never developed symptoms.]

In the interest of brevity, I will just bullet the papers (three of them are “pre-publication” versions that have not been formally peer reviewed because researchers are being encouraged not to “sit on” information that may be of use to others) and their conclusions here:

“We discovered that shedding of potentially infectious virus may occur in persons who have no fever and no signs or only minor signs of infection.”

(Albeit in 2 of 114-- or less than 2%)

Frankfurt team of physicians, letter to NEJM, Feb 18

Building on this initial work, the Frankfurt team more recently tested 24 passengers, this time travelers returning from Israel. Seven tested positive-- four of whom showed no symptoms. So now instead of 2 out of 114, we’re at 4 out of 7: more than half. The disturbing part, although of course this is one little snapshot at one point in time in a handful of people, was their observation that the viral load from the asymptomatic people was higher than the viral load of those who did have symptoms.

Other citations for asymptomatic, or what some prefer to label “pre-symptomatic” spread, include:

Estimating the generation interval for COVID-19 based on symptom onset data

Transmission interval estimates suggest pre-symptomatic spread of COVID-19

Clinical presentation and virological assessment of hospitalized cases of coronavirus disease 2019 in a travel-associated transmission cluster

Researchers found very high levels of virus emitted from the throat of patients from the earliest point in their illness —when people are generally still going about their daily routines. Viral shedding dropped after day 5 in all but two of the patients, who had more serious illness.

This pattern of virus shedding is a marked departure from what was seen with the SARS coronavirus, which ignited an outbreak in 2002-2003. With that disease, peak shedding of virus occurred later, when the virus had moved into the deep lungs.

Shedding from the upper airways early in infection makes for a virus that is much harder to contain.

The scientists said at peak shedding, people with Covid-19 are emitting more than 1,000 times more virus than was emitted during peak shedding of SARS infection, a fact that likely explains the rapid spread of the virus.

What does this mean on a practical level? I can only speak for myself, but after reading these reports I am no longer taking comfort in the fact that those around me show no symptoms of infection. And I have stopped making house calls to an 80 year old patient because I can no longer feel confident that just because I feel like I’m safe to be around doesn’t mean that I am.

Read Liz’s full reporting here.

Newer stories filed after I first posted this blog:

“Just because a coronavirus test says you don’t have the virus doesn’t mean you aren’t infected — or infectious”

NYT, April 1

“As many as 25% of people infected with the new coronavirus may not show symptoms”

per, however belatedly, the  CDC as reported by NYT, March 31

Not wearing masks to protect against coronavirus is a ‘big mistake,’ top Chinese scientist says

China CDC, as reported in Science, March 27

"Most chilling study - undocumented infections were the infection source for 79% of documented cases”

as shared by Eric Feigl-Ding on Twitter, March 20, referring to paper he’d read in Science a few days earlier

Substantial undocumented infection facilitates the rapid dissemination of novel coronavirus (SARS-CoV2)

Science, March 16

* For South Korea, the Asian country that has suffered the biggest outbreak aside from China, testing has been a key pillar in its strategy for combating the outbreak.  At drive-through testing facilities, officials clad in white hazmat suits can be seen leaning into cars to take fluid samples. And test results are returned in a matter of hours, helping to reduce crowding and contamination exposure at hospitals. Even more ubiquitous are alerts flashing on smartphone screens updating the public on new infections in their area, as well as health officials’ twice-daily broadcasts updating containment efforts. The focus on open communication, coupled with an online system to track those people who have been infected, has helped limit the spread of the virus. Rigorous testing and community responses have likewise dramatically limited spread in Hong Kong, Taiwan and Singapore, each country reporting little more than 200 cases. As reported by reporters in Taipei and Seoul yesterday in the FT.

Mike Barr is a long time POZ contributor, scribe for the Act Up/T+D Committee & Treatment Action Group, and pharmaceutical ghost writer né alternative health aficionado. He is a licensed acupuncturist and herbalist in NY and NJ, tending to folks in Union Square, Boerum Hill and Hoboken. Reach out to him at evacupuncturist at that Google mail service or at