Question

• Using John Snow's work on the Soho outbreak as an example, identify and explain the three parts of the epidemiological triangle.
• Explain how John Snow intervened in the relationships between the three parts of the triangle that you defined and what is the implication of his intervention.

Answer 1

The epidemiological triangle is a model which explains the three components that is agents, host and environment for any disease.

An AGENT is any micro-organisms which causes the disease for example bacteria, virus, parasites or fungus.

A HOST is the organisms which carries the disease and which is infected by an agent, it may get affected due to the disease or may not.

An ENVIRONMENT is nothing but the various factors which affects the spreading of the disease. These affect can positive or negative.

In Soho, London (1831) a disease was spread very quickly and it was believed that the disease is a contagious disease. John snow a physician found that the cholera was affecting the gastrointestinal tract instead of showing the pulmonary symptoms as it was believed that it was a contagious disease therefore he started his survey and collected the information from the victims of cholera where he found that the people are getting affected due to the contaminated water. snow went through municipal records noticed that two companies "Southwark & Vauxhall" supplied water to the localities from downstream location through the hand pumps wells which was contaminated with various microbes and the people living in this localities showed the cholera symptoms. But this was unacceptable because he could not provide any strong proof for this. Again in 1853 the cholera broke out but water samples resembled like the normal water samples. He continued his survey and found that majority of the victims consumed the water coming from the pump located at 'Broad street'. This pump was declared as a source of outbreak because the businesses which had their own water supply were not infected by the cholera and the businesses which were utilizing the water from Broad street pump showed cases of cholera which was then removed.

Later his studies showed that the cholera was caused due the the fecal matter of first cholera victim which was emptied into the cesspool located near to the pump leading to the leakage of water from cesspool to the pump water stream and causing the disease.

snow's implications on cholera lead to,

1. Prevention of further spreading of cholera.

2. Rise to Epidemiology.

3. Research for the causative agents, respective antibiotics and treatments for cholera.

4. Sanitation and water Hygiene

The investigation by Snow came to conclusion that the cholera was caused due to the consumption of water contaminated by the causative agents which entered the water through fecal matter of an infant which was the first case of cholera. His studies provided the scope of study for Epidemiology.