Today, any one of us could be spreading the coronavirus unknowingly. That is the implication of two key phrases that should be top of mind for everyone: “community spread” and “asymptomatic transmission.” A third phrase that may within days or weeks be on the front page is “overwhelmed health care system” — do not assume you will have a mild case and do not assume you will get the care you need if you become critically ill. All levels of government should be offering the strongest possible leadership on “social distancing.” Governor Baker’s recent announcements appear further below.
On Friday, March 13, the Massachusetts Department of Public Health issued guidance to health care providers acknowledging that “Massachusetts has now begun to see some initial evidence of community spread of COVID-19.” That means that the virus has broken out of known person-to-person chains of infection. It is no longer, “I had dinner with a friend from China who was coughing.” People are being diagnosed with the disease but no one knows where they got it. The virus is loose in the community and anyone could have it. Right now, the chance that you personally already have the virus is still very low, but the virus is likely spreading exponentially so the odds are getting worse by the day.
It is easy to get the disease from another person. The CDC says, “The virus that causes COVID-19 seems to be spreading easily and sustainably in the community (“community spread”) in some affected geographic areas.”
The stories about the Biogen meeting paint a grim picture of just how easy it is to spread the virus and how far out of control the virus likely already is. First contemplate that, as the Globe reported on March 11, roughly 50 out of 175 conference attendees had been identified as sick within days of the conference. Apparently these cases derived from perhaps just two conference attendees from Europe. Business meetings can involve a lot of warm greetings and shared meals, but there has been no suggestion that this meeting involved any truly unusual behavior that might elevate the rate of transmission. As of March 14, two weeks after the meeting ended, 104 people have tested positive who can trace their exposure to the conference.
Now, appreciating how easy it is to spread the disease in normal social interaction, contemplate that the conference ran from February 26 to February 27 and that it was not until March 7, more than a week after the conference, that 60 Marriot Employees were brought over to Brigham for testing. Then on March 12, two weeks after the conference ended, public health authorities closed the Marriot “in the interest of public health.” Consider all the hotel servers, doormen, desk clerks, and room cleaners who were likely exposed to the virus, not to mention other guests and workers in nearby restaurants. The Reddit thread about the Marriot employees includes a lot of telling comments, for example: “I guess it’s just scary how relevant it is to my life now, since I’m clearing dirty dishes and napkins all day. Also people are just super gross in general.” There was little explanation offered for the closure, but it is a fair inference that after another two weeks of working together some employees were sick and basically all the employees of the hotel should be quarantined and the entire hotel sanitized. Consider all of their family members exposed over the days of delayed response. Again, not to mention a new population of guests who cycled through the hotel.
The “serial interval” is the number of days between a person getting infected and a person infecting the next person in the chain of infection. Emerging literature from China (collected here) suggests that the serial interval averages around 5 days for COVID-19. The delayed responses to the emerging cluster gave plenty of time for the virus to spread among employees of both Biogen and the hotel and, of course, their families and friends.
Finally, set this story against the backdrop of a shortage of testing. The Globe reported that many of the Biogen employees who sought testing were initially turned away. More recently the Globe quoted a physician on the South Shore, “I feel, as a physician, like I’m pretty paralyzed by this, I think that’s the only word I can use. Paralyzed. I’ve never been in a position like this in my life . . . It’s been very strange to want to test for something, and have a high clinical suspicion for something, and not be able to do it.” See also the physician’s Faceboook thread. In the absence of a definitive diagnosis through testing, it is less likely that symptomatic people or their employing organizations will take all necessary precautions to avoid infecting others. For example, it took 5 days from the first employee showing symptoms for a general warning to go out to Biogen employees, during which time many Biogen employees mixed with those who attended the conference.
As of March 15, 2020, the official CDC position is that most transmission of the virus occurs when people are symptomatic — coughing and spewing drops of mucus and saliva that are teaming with viruses. The CDC says:
People are thought to be most contagious when they are most symptomatic (the sickest).
CDC, How It Spreads as of March 15, 2020
Some spread might be possible before people show symptoms; there have been reports of this occurring with this new coronavirus, but this is not thought to be the main way the virus spreads.
Update: As of April 2, the CDC now acknowledges asymptomatic spread.
Some recent studies have suggested that COVID-19 may be spread by people who are not showing symptoms.CDC, How It Spreads as of April 2, 2020
The World Health Organization goes a little further. While similarly discounting the risk of asymptomatic spread, WHO acknowledges the possibility of spread through people with mild symptoms:
The main way the disease spreads is through respiratory droplets expelled by someone who is coughing. The risk of catching COVID-19 from someone with no symptoms at all is very low. However, many people with COVID-19 experience only mild symptoms. This is particularly true at the early stages of the disease. It is therefore possible to catch COVID-19 from someone who has, for example, just a mild cough and does not feel ill. WHO is assessing ongoing research on the period of transmission of COVID-19 and will continue to share updated findings.WHO, News Room Q&A, as of March 15, 2020
Update: As of April 2, the WHO no longer discounts asymptomatic spread.
People can catch COVID-19 from others who have the virus. The disease can spread from person to person through small droplets from the nose or mouth which are spread when a person with COVID-19 coughs or exhales. These droplets land on objects and surfaces around the person. Other people then catch COVID-19 by touching these objects or surfaces, then touching their eyes, nose or mouth. People can also catch COVID-19 if they breathe in droplets from a person with COVID-19 who coughs out or exhales droplets. This is why it is important to stay more than 1 meter (3 feet) away from a person who is sick.WHO, News Room Q&A, as of April 2, 2020 (emphasis added).
It seems scientifically clear that asymptomatic transmission does, in fact, occur sometimes. A recent letter in the New England Journal of Medicine carefully documents a chain of asymptomatic COVID-19 transmission.
The fact that asymptomatic persons are potential sources of 2019-nCoV infection may warrant a reassessment of transmission dynamics of the current outbreak.Transmission of 2019-nCoV Infection from an Asymptomatic Contact in Germany, NEJM, March 5, 2020
What is not clear is what portion of all transmission is asymptomatic — it could be a lot. A non-specialist’s review of emerging literature from Asia concluded that the serial interval is less than the incubation period for COVID-19. In other words, people are typically transmitting the virus before they have symptoms. The reviewer explicitly did not claim that this finding was “settled science:”
Strong evidence points to presymptomatic sources as a major source of COVID-19 infections, possibly the majority. The exact proportion is environment-dependent; awareness and public health measures reduce symptomatic transmission more than they reduce presymptomatic transmission.A Significant Portion of COVID-19 Transmission Is Presymptomatic, LessWrong, March 14, 2020
Some experts are convinced that people who feel more or less fine are an important part of spreading the virus:
Asymptomatic and mildly symptomatic transmission are a major factor in transmission for Covid-19. . . . They’re going to be the drivers of spread in the community.Dr. William Schaffner, identifed by CNN as a professor at Vanderbilt University School of Medicine and longtime adviser to the CDC
National leaders are starting to recognize the possibility of asymptomatic spread:
Until you really understand how many people are asymptomatic and asymptomatically passing the virus on, we think it’s better for the entire American public to know that the risk of serious illness may be low, but they could be potentially spreading the virus to others. That’s why we’re asking every American to take personal responsibility to prevent that spread.Dr. Deborah Birx, national coronavirus response coordinator quoted by CNN.
Finally, back to the Biogen conference, it appears that none of the participants has admitted being symptomatic at the time of the conference. The likelihood of asymptomatic spread makes our current shortage of testing all the more troubling. If people are not seeking testing until they have symptoms, then with many people still going about their business in our limited shutdown, a lot of transmission is likely going on.
Overwhelmed Health Care System
The reassuring mantra is that, “Most people will have mild disease and get better without needing any special care.” That appears be a consistent finding and the true mortality rate is hard to know because many cases may go undiagnosed. On the other hand, many people, including some young people, do need hospitalization. The heartbreaking testimony from Italy shows that if the epidemic is not controlled it can overwhelm the best health care systems in the world, forcing doctors to ration lifesaving care. Italy has more hospital beds per capita than we do — it can happen here.
So, as more and more people understand, the challenge is to “flatten the curve” so that when the epidemic peaks, we still have enough capacity to care for people. The New York Times has a lovely graphic opinion piece about how bad things could get. One of the key takeaways is that it’s way too late to worry about stopping incoming cases. We have thousands of people sick and they are transmitting rapidly enough to double the case load every six days. In the absence of effective vaccines or drug treatments, we just have to move more quickly on social distancing and that is not easy politically.
Early in the epidemic it is very difficult to muster the political will to implement costly, disruptive disease-control policies. . . . What we are hoping to show here is that the calculus is one of short-term pain for long-term gain: Early, aggressive social distancing can substantially reduce the toll of epidemics, which can include the near collapse of health care systems, as we’re currently seeing in Italy.Epidemiologist David Fisman, Quoted in New York Times, March 13
Many voices are calling for a much more aggressive social distancing program led by government. I join those voices and will be advocating for that in every way I can.
- Social Distancing — this is not a snow day
- Coronavirus: Why You Must Act Now
- State and Local Governments Must Take Much More Aggressive Action Immediately To Slow Spread of the Coronavirus
- Newt Gingrich in Newsweek: I Am in Italy Amid the Coronavirus Crisis. America Must Act Now—And Act Big
- Medium: Act today or people will die
It’s wrong to claim certainty, but the epidemiological analysis suggests that the costs of delay could be unacceptable. Now is the time to pull all the levers we can reach to slow the spread. Close bars, restaurants, and entertainment venues, close the schools, work on messaging to parents and kids about staying home instead of walking the malls . . . get ahead of the epidemic, rather than waiting for it to hit in its full viral fury.
Actions taken by Governor Baker on Sunday, March 15 at 6PM
- Close all the schools in the state for 3 weeks.
- Prohibit on-premise service of food or drink in restaurants or bars (but permitting take out food).
- Prohibit gatherings of over 25 people, excepting legislative bodies and the courts.
- Limit visitors to nursing homes and long-term care facilities.
- Expedite licensing of nurses from other states (previously ordered)
- Anticipated or informal actions
- Directive to all health insurers to cover telehealth services
- Registry of Motor Vehicles guidance extending renewals so people residents do not need to visit the RMV for renewals at present
- Directing hospitals to cancel all elective procedures beginning on Wednesday to create additional capacity in hospitals to treat COVID-19 patients
- Filing emergency legislation on Monday 3-16 to relax Unemployment Insurance guidelines, including waiving the one week waiting period to collect unemployment and expanding eligibility for collecting unemployment for people who have been impacted by COVID-19
- Filing emergency legislation on Monday to help municipal governments with town meetings and adopting budgets
I fully support these actions. They are a big step forward. We likely need to go further very soon, but these were the key next steps that I have been advocating for — I had focused particularly on the school closures. I look forward to hearing from people on additional steps that seem appropriate.
Thank you to many constituents for sharing insights on the pandemic with me. Special thanks to Ben Kuhn who identified many of the resources cited to in this piece. See also the epidemic visualization he developed.