John Snow Cholera Pdf
• Student Instructions: John Snow’s Classic Studies of Cholera Epidemics in London 1854 (1/student) –Make a class set: These sheets can be laminated or placed in transparency sleeves to be used in all of your classes. John Snow’s well known cholera map is often cited as one of the earliest known examples of using geographic inquiry to understand a health epidemic. Starting on August 31, 1854, an outbreak of cholera hit the London district called Soho.
How often does a map change the world? In 1854, one produced by Doctor John Snow, altered it forever.
- JOHN SNOW, M.D. LONDON: JOHN. CHURCHILL, PRINCES. STREET, SOHO. MODE OF COMMUNICATION OK CHOLERA. It is not the intention of the writer to go over the much debated question. Be the mode of communication of. Cholera; and it. Be confessed that it is difficult.
- Struck London during the third pandemic, in 1854. A London anaesthetist, John Snow, had already developed an interest in cholera during the second pandemic, in 1831. By 1849, he was suggesting that a water-borne agent that entered by the mouth, multiplied in the gut and left via the faeces, was the cause of cholera.
- John Snow's accomplishments in medicine, anesthesia, and epidemiology constituted an achievement that changed the face of medical practice. The most unpleasant aspect of Snow's theory was that cholera victims were infected by swallowing other people's fecal matter. On the Mode of Communication of Cholera. London: John Churchill, 1855.
In the world of the 1850s, cholera was believed to be spread by miasma in the air, germs were not yet understood and the sudden and serious outbreak of cholera in London's Soho was a mystery.
So Snow did something data journalists often do now: he mapped the cases. The map essentially represented each death as a bar, and you can see them in the smaller image above.
It became apparent that the cases were clustered around the pump in Broad (now Broadwick) street.
There were some outliers though and Snow wrote that:
In some of the instance , where the deaths are scattered a little further from the rest on the map, the malady was probably contracted at a nearer point to the pump
One 59-year-old woman sent daily for water from the Broad street pump because she liked its taste. Wrote Snow:
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 the water from the pump in Broad Street, as she preferred it. The water was taken on Thursday 31st August., and she drank of it in the evening, and also on Friday. She was seized with cholera on the evening of the latter day, and died on Saturday
John Snow Investigation Of Cholera
At a local brewery, the workers were allowed all the beer they could drink - it was believed they didn't drink water at all. But it had its own water supply too and there were consequently fewer cases.
In nearby Poland street, a workhouse was surrounded by cases but appeared unaffected: this was because, again, it had its own water supply.
John Snow Cholera Pdf Free
It turned out that the water for the pump was polluted by sewage from a nearby cesspit where a baby's nappy contaminated with cholera had been dumped. But he didn't just produce a map; it was one part of a detailed statistical analysis.
As the Public Health Perspectives blog says, it changed how we see data visualisations, and how we see microbes. Snow was born 200 years ago this week and is the subject of an exhibiton at the London School of Hygiene and Tropical Medicine.
But how would those deaths look for a data journalist today?
Thanks to Robin Wilson at Southampton University, we have the data. Robin painstakingly georeferenced every cholera death and pump location, so we could recreate the map on a modern layout of London. We wondered what would happen if we tried to recreate the map using a modern tool, opting to try CartoDB, using the the lovely Stamen 'toner' projection to at least keep the background in common with Snow's London.
An interactive version
As XKCD have pointed out, heatmaps or dotmaps have flaws, not least that they tend to show where the people are.
And the alternative is usually to aggregate the data, so that you could show, say, the incidence of cholera by geographical area - a choropleth. But in this case, would that have worked?
The cluster of dots around the Broad street pump were what alerted Snow to the cause of the outbreak.
Edward Tufte is interesting on this. He points out that
The big problem is that dot maps fail to take into account the number of people living in an area and at risk to get a disease … Snow's dot map does not assess varying densities of population in the area around the pump
But, as Tufte points out, this part of Soho was incredibly thickly populated. And 'aggregations by area can sometimes mask and even distort the true story of the data'. A choropleth map of the area might show that there was a cluster of cholera cases, but it might not, depending on where the boundaries are drawn. Mark Monmonier, author of How to lie with mapshas examined this.
But there's another key point here: in the event of an outbreak like this now, it's inconceivable that the government would publish the data on grounds of privacy; that the victims' addresses were personal data.
As data journalists, we agonise over how to represent the true impact of an event. Maps are often the first thing to reach for because it's easy: the tools are now just so easy to use and so much data is geographic. Although they are often mightily popular with readers, it's probably not always the right choice. Trying harder to show the data in different ways is an honourable objective.
But when they work, maps can tell a story in a language that everyone can understand.
Maybe Snow's map had such a huge impact on its own because it was simply a great data visualisation.
Robin Wilson has given us links to the data below. What can you do with it?
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Contents
Though cholera has been around for many centuries, the disease came to prominence in the 19th century, when a lethal outbreak occurred in India. There have since been numerous outbreaks and seven global pandemics of cholera. Each year, cholera infects 1.3 to 4 million people around the world, killing 21,000 to 143,000 people, according to the World Health Organization (WHO).
What Is Cholera?
Cholera is an infectious disease caused by a bacterium called Vibrio cholerae. The bacteria typically live in waters that are somewhat salty and warm, such as estuaries and waters along coastal areas. People contract V. cholerae after drinking liquids or eating foods contaminated with the bacteria, such as raw or undercooked shellfish.
There are hundreds of strains or “serogroups” of the cholera bacteria: V. cholerae serogroups O1 and O139 are the only two strains of the bacteria known to cause outbreaks and epidemics.
These strains produce the cholera toxin that cause cells lining the intestines to release increased amounts of water, leading to diarrhea and rapid loss of fluids and electrolytes (salts). A single diarrhea episode can cause a one-million-fold increase of bacterial numbers in the environment, according to the National Institute of Allergy and Infectious Diseases.
Cholera Symptoms
About 80 percent of people who contract the bacteria don’t develop cholera symptoms and the infection resolves on its own. And of the people who do develop cholera, 20 percent come down with severe symptoms, which includes severe diarrhea, vomiting, and leg cramps. These symptoms can cause dehydration, septic shock and even death within a matter of just a few hours.
People who contract non-01 or non-1039 V. cholerae can also acquire a diarrheal disease, but it is less severe than actual cholera.
Today, cholera is treated through fluid replacement and antibiotics. Cholera vaccines are available, though they only offer roughly 65% immunity, according to WHO.
Origins of Cholera
It’s unclear when, exactly, cholera first affected people.
Early texts from India (by Sushruta Samhita in the 5th century B.C.) and Greece (Hippocrates in the 4th century B.C. and Aretaeus of Cappadocia in the 1st century A.D.) describe isolated cases of cholera-like illnesses.
One of the first detailed accounts of a cholera epidemic comes from Gaspar Correa—Portuguese historian and author of Legendary India—who described an outbreak in the spring of 1543 of a disease in the Ganges Delta, which is located in the south Asia area of Bangladesh and India. The local people called the disease “moryxy,” and it reportedly killed victims within 8 hours of developing symptoms and had a fatality rate so high that locals struggled to bury all the dead.
Numerous reports of cholera manifestations along the West coast of India by Portuguese, Dutch, French and British observers followed throughout the next few centuries.
The First Cholera Pandemic
The first cholera pandemic emerged out of the Ganges Delta with an outbreak in Jessore, India, in 1817, stemming from contaminated rice. The disease quickly spread throughout most of India, modern-day Myanmar, and modern-day Sri Lanka by traveling along trade routes established by Europeans.
By 1820, cholera had spread to Thailand, Indonesia (killing 100,000 people on the island of Java alone) and the Philippines. From Thailand and Indonesia, the disease made its way to China in 1820 and Japan in 1822 by way of infected people on ships.
It also spread beyond Asia. In 1821, British troops traveling from India to Oman brought cholera to the Persian Gulf. The disease eventually made its way to European territory, reaching modern-day Turkey, Syria and Southern Russia.
The pandemic died out 6 years after it began, likely thanks to a severe winter in 1823–1824, which may have killed the bacteria living in water supplies.
Cholera Infects Europe and the Americas
The second cholera pandemic began around 1829.
Like the one that came before it, the second pandemic is thought to have originated in India and spread along trade and military routes to Eastern and Central Asia and the Middle East.
By autumn of 1830, cholera had made it to Moscow. The spread of the disease temporarily slowed during the winter, but picked up again in spring of 1831, reaching Finland and Poland. It then passed into Hungary and Germany.
The disease subsequently spread throughout Europe, including reaching Great Britain for the first time via the port of Sunderland in late 1831 and London in spring of 1832. Britain enacted several actions to help curb the spread of the disease, including implementing quarantines and establishing local boards of health.
But the public became gripped with widespread fear of the disease and distrust of authority figures, most of all doctors. Unbalanced press reporting led people to think that more victims died in the hospital than their homes, and the public began to believe that victims taken to hospitals were killed by doctors for anatomical dissection, an outcome they referred to as “Burking.” This fear resulted in several “cholera riots” in Liverpool.
In 1832, cholera had also made it to the Americas. In June of that year, Quebec saw 1,000 deaths from the disease, which quickly spread along the St. Lawrence River and its tributaries.
Around the same time, cholera imported into the United States, appearing in New York and Philadelphia. Over the next couple of years, it would spread across the country. It reached Latin America, including Mexico and Cuba, in 1833.
The pandemic would die out and reemerge throughout numerous countries for nearly two decades until it subsided around 1851.
John Snow
Between 1852 and 1923, the world would see four more cholera pandemics.
The third pandemic, stretching 1852–1859, was the deadliest. It devastated Asia, Europe, North America and Africa, killing 23,000 people in Great Britain alone in 1854, the worst single year of cholera.
In that year, British physician John Snow, who’s considered one of the fathers of modern epidemiology, carefully mapped cholera cases in the Soho area of London, allowing him to identify the source of the disease in the area: Contaminated water from a public well pump.
He convinced officials to remove the pump handle, immediately dropping the cholera cases in the area.
The fourth and fifth cholera pandemics—occurring 1863–1875 and 1881–1896, respectively—were overall less severe than previous pandemics, but had their fair share of deadly outbreaks. Between 1872 and 1873, for example, Hungary suffered 190,000 deaths from cholera. And Hamburg lost nearly 1.5 percent of its population due to cholera in the 1892 outbreak.
In 1883, German microbiologist Robert Koch, the founder of modern bacteriology, studied cholera in Egypt and Calcutta. He developed a technique allowing him to grow and describe V. choleraeFilelist xml txt far cry 4 ps4. , and then show that the presence of the bacterium in intestines causes cholera.
However, Italian microbiologist Filippo Pacini had actually identified the cholera bacterium—naming it cholerigenic vibrios—in 1854, though this fact wasn’t widely known (and was likely unbeknownst to Koch).
During the fifth pandemic, Great Britain and the United States were mostly safe thanks to improved water supplies and quarantine measures.
The sixth cholera pandemic (1899–1923) largely didn’t affect western Europe and North America due to advances in public health and sanitation. But the disease still ravaged India, Russia, the Middle East and northern Africa. By 1923, cholera cases had dissipated throughout much of the world, except India—it killed more than half a million people in India in both 1918 and 1919.
Cholera Today
Unlike previous pandemics, which all originated in India, the seventh and current cholera pandemic began in Indonesia in 1961. It spread across Asia and the Middle East, reaching Africa in 1971. In 1990, more than 90 percent of all cholera cases reported to WHO were from the African continent.
In 1991, cholera appeared in Peru, returning to South America after being absent for 100 years. It killed 3,000 people in Peru in this first year and subsequently spread to Ecuador, Colombia, Brazil and Chile, and then Central America and Mexico.
Though the current cholera pandemic has affected some 120 countries, it’s largely a disease of impoverished, less-developed nations.
In recent years, there have been a number of devastating outbreaks, including the Zimbabwe outbreak of 2008–2009 that affected some 97,000 people (killing 4,200) and the Haiti outbreak of 2010–2011, which followed the Haiti earthquake and would affect more than 500,000 people.
In 2017, outbreaks of cholera broke out in Somalia and Yemen. By August 2017, the Yemen outbreak affected 500,000 people and killed 2,000 people, making it the largest cholera epidemic in the world today, according to WHO.
Sources
Cholera. World Health Organization.
What Is Cholera? Everyday Health.
Boucher et al. (2015). “The out-of-the-delta hypothesis: dense human populations in low-lying river deltas served as agents for the evolution of a deadly pathogen.” Frontiers in Microbiology.
Cholera studies. 1. History of the Disease. Bulletin of the World Health Organization.
Non-O1 and Non-O139 Vibrio cholerae Infections. Centers for Disease Control and Prevention.
Gill et al. (2001). “Fear and frustration—the Liverpool cholera riots of 1832.” The Lancet.
Kelley Lee (2001). “The Global Dimensions of Cholera.” Global Change and Human Health.
Cholera’s seven pandemics. CBC News.
Cholera count reaches 500 000 in Yemen. WHO.