The man who invented epidemiology
When the Cholera outbreak struck London in the mid 19th century the dominant approach was that it was airborne, a product of polluted air traveling about. It wasn’t so much of an approach as a well known, age-old, convention. The “Miasma” theory held also for other infectious diseases such as the black death and shaped the strategy of combating the outbreak.
In 1854, a terrible Cholera outbreak shook the city of London and mainly the Soho area. Hundreds died, many more critically ill. John Snow (not the dragon-flying guy, a Doctor) took a good look at the data and felt something was off. Snow assessed that there is a different reason that is causing the disease to spread, that polluted air can not explain what was going on. He concluded, or maybe half guessed, that contaminated water is to blame, and in order to prove his point he started what we may call today an Epidemiologic inquiry.
Snow made a map of the area surrounding the worst-hit street in Soho, Broad st. He dotted dots representing specific cases. He found that most cases were linked to a water pump located on the street and that the people severely ill were all drinking contaminated water. Further proving his point, he found a group of workers from a local brewery, none were ill — they all got an unlimited supply of beer at work, never touched the water.
The data was so convincing that the government decided to replace the pump, although categorically rejecting his findings. The outbreak died down, years passed until Snow got the recognition he deserved. A symbolic Pump is located to this day on Broad (now Broadwick) street with a plaque honoring one of the founding fathers of a whole new field.
The secret might be right under our feet
166 years passed since and the sewer is recently turning into an important matter. Yes, it’s not ‘sexy’ to talk about sewage and yet this could be a major milestone in the fight against Covid-19. At the early stages of the disease, the virus was thought to attack the respiratory system, more and more evidence started to emerge indicating the potential damage could be more substantial. Chinese researches wrote about an Asymptomatic patient with traces of Covid-19 in stool and not in the respiratory system. Other patients started reporting digestive problems, trouble with their bowels, diarrhea, or vomiting, and researchers dove deep into the sewers to see if this could be used to our advantage.
All over the world sewage samples were taken and analyzed. Dutch researches found traces of Covid-19 before any cases were diagnosed and before any admission to the local hospital was made. This week another major study was published combining the work environmental engineers, agriculture experts, and epidemiologists from Yale University which found a substantial contribution of taking sewage samples to the fight against outbreaks. Signs of a potential cluster could be found in the sewer 3–7 days before Covid-19 test results or hospital admissions gave any clue to what might be going on. “Our study could have substantial policy implications. Jurisdictions can use primary sludge SARS-CoV-2 concentrations to preempt community outbreak dynamics or provide an additional basis for easing restrictions, especially when there are limitations in clinical testing” — The researches wrote and paved the way to a new strategy, one in which testing sewage could lead to an early discovery of a potential hotspot, a surgical lockdown is implemented and specific testing and treatment could prevent a disaster. This could be a gamechanger and huge news for countries with a lack of testing capabilities or a poor health system.
The new Covid-19 epicenters
The issue of Sewage is turning even more significant when looking at the trend in the past weeks. the center of the Covid-19 cases is shifting from the ‘first world’ to the ‘third world’. Africa is seeing an increase, Also parts of South America are badly hit. another question arises, could Covid-19 also be transferred through the sewer? The WHO and the American CDC say it’s unlikely. So far we haven't seen any major outbreaks in sewage workers, this is a good sign.
In the ‘first world’ most people have clean water and an efficient sewage system, this question might not be as important for them, however, in the ‘third world’ this could be the difference between an outbreak and a catastrophe.
John Snows' gut feeling, the questions he raised, against most researches and authorities, these are all turning today, at the peak of the Covid-19 era, to be critical. It might not smell so good but it is very important.