Today, we know that washing our hands is one of the most important steps we can take to avoid getting sick and spreading germs.

But how we came to know that is pretty fascinating.

Handwashing is actually a relatively new practice — even for doctors.

In fact, one of the first doctors to realize how important handwashing could be — Ignaz Semmelweis — didn’t discover this fact until 1847. And even after he did realize it, the battle to convince the rest of the medical community wasn’t easy.

The 19th century has been described by some historians as “a golden age of the physician and scientist” because for the first time, doctors were expected to have scientific training.

They were also expected to use symptom-based diagnoses to solve medical ailments. And to do this, of course, medicine relied on understanding what was happening inside the human body to get at the root of disease.

So, autopsies became all the rage.

Not only did they form a critical part of a doctor’s training, but the doctors who regularly performed them were the most respected in the medical community. An unfortunate byproduct of this, though, was the erroneous belief that the dirtier the doctor, the better the doctor.

In fact, there are accounts of doctors going directly from their last autopsy to deliver a baby or treat a patient without changing their clothes.

Enter Hungarian doctor Ignaz Semmelweis.

In 1846, Semmelweis had just started his new job at the maternity clinic at Vienna General Hospital.

At that time, women were dying at staggering rates in hospitals shortly after giving birth from “childbed fever,” a disease also called puerperal fever. It was a cruel infection, causing raging fevers, painful abscesses, an infection in the uterus and birth canal, sepsis, and then finally, death — all within about three days of the baby’s delivery. And it was the single most common cause of maternal death at the time.

Being a man of science, Semmelweis wanted to understand why so many women were dying in his clinic. So he studied two maternity wards in the hospital — one staffed by doctors and medical students, the other by midwives — and recorded the number of deaths in each ward.

His results showed that women died at a rate nearly five times higher in the ward staffed by doctors and medical students.

But it wasn’t until one of his colleagues, a pathologist, got sick and died after pricking his finger in an autopsy of someone who had died from childbed fever that Semmelweis realized that anyone, not just mothers, could get sick from puerperal fever, and the reason the midwives' ward had fewer deaths was because they didn't do autopsies.

He theorized that there must be some “cadaverous particles” or “morbid poison” that doctors were getting on their hands during autopsies. And the doctors in the ward were then transferring these particles inside the women when they delivered the baby, which then made the women sick.

Today, these “cadaverous particles” are known as bacteria, such as streptococcus pyogenes.

Semmelweis immediately ordered the medical staff to start cleaning their hands and instruments before delivering babies.

They were told to use a chlorine lime solution, not soap, until they could no longer smell the bodies they had dissected.

And it worked — chlorine is actually a great disinfectant. The rate of puerperal fever fell drastically in the doctor’s ward.

Unfortunately, the Semmelweis' colleagues did not embrace his findings — they were outraged at the suggestion that they were the cause of their patients' deaths. Semmelweis was fired from the hospital and eventually committed to an asylum. He died at the asylum two weeks later. (Several historians believe that he died, after being beaten at the asylum, from sepsis — an infection in the bloodstream caused by germs.)

It would take about 20 years before his ideas would start to be accepted by the medical community. And even then, it was "germ theory" — and the work of Louis Pasteur in the late-1860s — that really convinced anyone of the importance of hygiene and handwashing.

Over a 150 years later, though, Semmelweis is finally getting the recognition he deserves because the simple act of handwashing is one of the most important tools we have in public health.

And its benefits extend well beyond the hospital. Washing your hands reduces the chances of getting diarrheal illnesses by 31%, according to the Centers for Disease Control and Prevention (CDC). It also reduces the occurrence of respiratory illnesses — including colds — by 16 to 21%.

That’s why in the 1980s, the first nationally endorsed hand hygiene guidelines were released by the CDC, after a series of outbreaks of food-borne and health care-associated infections. And over the next few decades, a number of other guidelines have followed to stress the importance to the general public.

Today, the battle to promote this public health tool is still not over.

Diarrhea and respiratory infections remain leading causes of death in the developing world — claiming about 3.5 million children every year — because people either don't know how important handwashing is or don't have access to a reliable, clean water source. There are also still over 1.4 million cases of health care-associated infections around the world. But through education initiatives, NGOs all over the world are hoping to bring about change with this one simple habit.

Proper hand hygiene is still one of the best ways to fight these infections and diseases — and we have Dr. Semmelweis to thank.