Some Doctors Are Giving John Snow a Bad Name

On 15 October 2020, a group of some 30 medical scientists and academics published a letter titled “Scientific consensus on the COVID-19 pandemic: we need to act now” in The Lancet, see The authors reiterate details from the early, terrifying assessments of the public health threats from Sars-CoV-2. This includes the initial worry that the entire human population on earth might be susceptible to infection, owing to a lack of prior exposure; the infection-fatality rate of COVID-19 being “several-fold higher” than it is for the flu; and a claim that lockdowns were successful in slowing the spread of the virus.

To my knowledge these overly cautious assessments have been dispelled by recent research. For example, 80% to 90% of Sars-CoV-2 infections remain asymptomatic or show only mild symptoms, which must be due to existing cross-immunity from memory T cells; with an IFR now pegged at 0.27%, COVID-19 is in the ballpark of a severe flu cycle; and lockdowns in many countries have been shown to have no effect on the epidemic curve whatsoever. The Lancet letter also notes concerns about long-term impacts of Sars-CoV-2 infections, so called “Long COVID”. While it is too early in the pandemic to gauge the existence and magnitude of this risk, I believe that all respiratory diseases can lead to long-term illness in a small proportion of patients. The letter concludes with an invitation to co-sign the “John Snow Memorandum”, which calls for “continuing restrictions” in light of recent increases of COVID-19 case counts in Europe, North America, and elsewhere, and explicitly rejects approaches that include letting the virus spread through the healthy, non-vulnerable parts of the population.

Now you might ask, who on earth is John Snow? In PBS’s historic TV drama “Victoria” about the eponymous British queen, Dr. John Snow makes an appearance in Episode 4 of Season 3 (Fig. 1a). In a backgrounder about the show, Town & Country magazine introduces him with reference to his (almost-)namesake from the Games of Thrones series:

“Before there was Jon Snow, King of the North, there was a real-life hero of the same name. Back in 1854, a Dr. John Snow made a medical breakthrough that earned him the title ‘The Father of Epidemiology’, and his recent portrayal in the period drama Victoria has given us the excuse to celebrate his legacy once again.”

Chloe Foussianes in Town & Country magazine, 4 February 2019

Dr. Snow is in fact well-known to students not only of Epidemiology but also Geography and Cartography. He was a medical doctor and surgeon in London UK in the 1830s to 1850s. In addition to developing anaesthetic procedures for childbirth, he had taken an interest in the recurring cholera outbreaks in the city. In 1854, he identified the public water pump on Broad Street as the possible source of a deadly outbreak, after talking to affected residents and noticing a cluster of fatalities near the pump. Snow’s map with the deceased marked at their home locations is one of the most famous maps in Geography (Fig. 1b). According to Wikipedia, the outbreak may already have been on the decline when the local council agreed to Snow’s request to remove the pump’s handle, yet this decisive action is likely what made the Lancet letter authors adopt his name for their memorandum.

If I recall the episode of “Victoria” correctly, Broad Street residents actually tried to stop government agents from removing the pump handle as they liked the taste of the water and the convenient location. If we equate Dr. Snow’s intervention with today’s pandemic response, e.g. travel restrictions or limits on group sizes, we also see grassroots concerns and opposition to the authoritative measures. Interestingly, Wikipedia credits Snow’s findings for “fundamental changes in the water and waste systems of London, which led to similar changes in other cities, and a significant improvement in general public health around the world.” In other words, the importance of Snow’s contribution is not measured by the immediate crisis response but by evidence-based long-term solutions that address the challenge holistically. Indeed, epidemiology and public health are about healthy long-term living conditions for all, not about short-term solutions for some. Our epidemiologists better consider all aspects of global health rather than stare down one select virus that isn’t even that exciting!

Figure 2. Florida Governor Ron DeSantis introducing the experts invited to a virtual roundtable about the state’s COVID-19 response, 24 September 2020. Source: Screenshot from video posted at, which also has a transcript of the two-hour session.

In addition, 150+ years ago the authorities may have been expected to take drastic measures without consultation. Today, we have come to expect better communication from political decision-makers and their respect of individual rights and freedoms. In this context, I was hugely impressed by Florida governor Ron DeSantis. DeSantis held a virtual roundtable with infectious disease experts Drs. Jay Bhattacharya, Martin Kulldorff, and Michael Levitt on 24 September 2020. The impressive part was that this high-ranked politician personally led the conversation with these eminent academics in a purposeful way, demonstrated keen knowledge of COVID-19 related studies from around the globe, and even acted as a facilitator for questions from the media representatives in the room. I could not help but feel that none of the Canadian or German politicians that I know would have been able to pull this off. In addition, DeSantis decided the following day that the state would enter the final “reopening” phase, essentially dropping all restrictions on normal life for the majority of residents. He thereby demonstrated that politicians can listen to “the science” after all. Note that I had never heard of DeSantis before, and that I disagree with most of his other political positions.

Figure 3. The authors of the Great Barrington Declaration in an interview with alternative news site UnHerd. Source: screenshot from

Two of the Florida roundtable participants, Drs. Bhattacharya and Kulldorff from Standford and Harvard universities, along with Dr. Sunetra Gupta from Oxford University, initiated the Great Barrington Declaration about two weeks later. The Declaration recommends “focused protection” of vulnerable groups rather than general restrictions of the healthy, that is, returning to the approach that was the essence of pandemic response planning in most countries prior to this year. The John Snow Memorandum outlined at the beginning of this post was likely written in response to the Great Barrington Declaration, as the latter is often misrepresented as arguing for a “herd immunity strategy”. Herd immunity is the situation where enough members of a community have acquired natural immunity from a resolved infection or immunity from vaccination to prevent further epidemic spread of a disease. It therefore cannot be characterized as a “strategy”, but it is the outcome of any epidemic, though different public health responses can yield herd immunity sooner or later, with direct implications on the death toll and collateral damage. For example, I recently saw a research report that found higher COVID-19 fatalities caused by lockdowns – in addition to the collateral damage (non-COVID deaths) also attributed to lockdowns.

My knowledge of Game of Thrones if severely limited to Season 8 of the TV adaptation, but my understanding is that Jon Snow, King in the North, worked selflessly to unite the seven kingdoms in a joint fight against a terrifying external enemy, the Night King’s army, despite long-standing animosities between the royal families of Westeros. Maybe we need a Jon Snow Memorandum rather than a John Snow Memorandum today? Winter is coming…, and with it, we can expect a new wave of respiratory illnesses, mostly likely including COVID-19 or its next genetic strain. Nevertheless, if acute-care physicians and nurses, health-care managers, public health officers, epidemiologists, immunologists, microbiologists, virologists, modellers, data scientists, and other experts could set aside their idiosyncrasies and work together, we might be able to return to our old normal along with monitoring of public health metrics that are already in place, ambulatory and hospital capacities ready to be activated and expanded, all treatment options seriously examined, immune system welfare and prevention in focus, and a generally more relaxed attitude towards Sars-CoV-2.