COVID-19 – Is Lombardy the Widow of Hampstead?

April 18, 2020

Tom Jefferson,  Maurizio Bonati, Carl Heneghan


In September 1854 John Snow was investigating the outbreak of pandemic cholera centred around Broad Street in London. 

His colleague Doctor Frazer of Oakley Square showed Snow the record of the death of a 59-year-old widow who died after 16 hours of agony. Snow had formulated a causal hypothesis which was at odds with the prevalent miasma theory: cholera was transmitted via the oro-faecal route from the contaminated water of Broad Street pump. 

The death of the widow of Hampstead was difficult to reconcile with Snow’s theory as Hampstead had a different source of water than Soho. Snow decided he would investigate further and walked 7 km to the home of the deceased. 

Snow reports: “I was informed by this lady’s son that she had not been in the neighbourhood of Broad Street for many months. A cart went from Broad Street to West End every day and it was the custom to take out a large bottle of water from the pump in Broad Street, as she preferred it. The water was taken on Thursday the 31st of August and she drank of it on the evening, and also on Friday” she died two days later. 

Snow understood the importance of an outlier to explain or refute his theory. He investigated the extraordinary to shed light on the ordinary. Similarly, the events of the beginning of March 2020 in Lombardy should be thoroughly investigated to understand the transmission dynamics of COVID-19. 

Linked to this post is an accurate description of the two areas and why they are outliers:

EDITORIALE: Perché la Lombardia è un outlier: un’anomalia evidenziata dalla Covid-19. I Lombardi fall  ( Italian pdf) Maurizio Bonati

English translation: Lombardy an outlier in the Covid-19 pandemic


We now require a series of hypotheses that can be tested to shed light on the transmission dynamics. We should use this unique opportunity to use the extraordinary to shed light on the ecology of COVID-19.

In this way, the widow of Hampstead and the Lombardy victims will not have died in vain.


Tom Jefferson is a senior associate tutor and honorary research fellow, Centre for Evidence-Based Medicine, University of Oxford. Disclosure statement is here

Maurizio Bonati is Head of the Department of Public Health, Mario Negri Institute of Milan, a private no-profit research Institute. He is an academic contract professor (without salary) at the University of Milan and at University of Pavia (Psychiatric Child Health teaching).  He participates in numerous public technical tasks free of charge, and has no working or consulting relationship with any industry or institutions.

Carl Heneghan is Professor of Evidence-Based Medicine, Director of the Centre for Evidence-Based Medicine and Director of Studies for the Evidence-Based Health Care Programme. (Full bio and disclosure statement here)