Look at your hand right now. Or your mobile phone screen. Or anything around you for that matter.

You might not see anything other than the objects literally in front of you, but there are really millions of animals moving about the surface. It’s just that they are so minute that you can’t see them with your naked eye.

Germs are mostly harmless to humans, and some can even be beneficial, but others not so much.

While they are indeed tiny in size, germs can destroy creatures far larger than themselves, wreaking havoc from the inside.

Illnesses from germs can be as mild as coughs and flus, or potentially deadly like the new coronavirus called Covid-19.

If not for the protection provided by your immune system, the impact that germs would leave on you could be devastating or even lethal.

But while it may now be common knowledge that diseases are caused by germs, that was not always the case.

Before the idea that diseases were caused by germs, or germ theory, emerged, medical experts believed in the miasma theory, that suggested diseases were caused by “bad air” called miasma.

This miasma theory was accepted for centuries before the facts started to emerge in the middle of the 19th century.

In the 1840s, London was a terrible place to live; polluted, dirty and a site of frequent and deadly cholera outbreaks.

By then, microorganisms had been discovered through the lenses of microscopes, but the connection between them and the diseases they caused was not yet made.

Because of how prevalent the belief in the miasma theory was by then, the germ theory failed to gain traction.

But for an Englishman named John Snow, he knew something had to be done to change the minds of the medical community.

Dr Snow noted that those infected with cholera experienced vomiting and diarrhoea, which suggested that cholera was an infection of the gut rather than the lungs.

Therefore, it was likely something that the patients had eaten or drank rather than breathed.

He hypothesised that cholera was being spread by contaminated water, and he got his chance to prove it when a cholera outbreak occurred in 1854.

Residents of London’s Soho District were stricken with cholera and Dr Snow noted the details of all the deceased victims.

He soon noticed a trend: Most of the victims had been using water from the same water pump on Broad Street.

Figuring that the pump was the source of the outbreak, he suggested to the authorities that they seal off the pump, saying the water could be poisoned.

Eventually though reluctantly, the authorities agreed and shut down the pump.

The results were immediate as the number of victims plunged.

He soon started to build his case by continuing his investigations.

A woman who had died of cholera outside the Soho District was found to have drank the water from the pump, supposedly because the taste was to her liking.

And within the Soho District was a workhouse which was barely affected by the outbreak.

Looking into this, Dr Snow learnt that the workhouse had its own well, which meant that its occupants had not been drinking water from the pump.

A damning piece of evidence was found when Dr Snow discovered that the soiled diapers of a baby, who would later fall victim to the outbreak, had been dumped into a cesspool next to the pump.

Dr Snow presented his evidence to the authorities, who rejected it as it was hard to stomach the idea that they had been drinking human waste.

And it didn’t help that the medical community was still largely holding onto the outdated and inaccurate miasma theory.

While Dr Snow died of a stroke just four years later, his ideas would not die with him.

He was vindicated in 1884 when German scientist, Dr Robert Koch, found the bacteria that causes cholera and proved the link between germs and diseases.

At the same time, French scientist Louis Pasteur was developing the first vaccines to counter diseases that had run rampant for so long.

Today, Dr Snow is considered the father of epidemiology as his work would further progress in medical science and herald breakthroughs in medicine and public health.

With the lessons learnt through the work of dedicated scientists, humanity has yet another weapon in its age-old war against disease.