Unit 10 · The Germ Revolution

In the 1700s, smallpox killed many people in every part of the world. Those who lived often had deep scars. In the English countryside, people noticed something strange. Milkmaids who had caught cowpox, a mild disease from cows, seemed not to catch smallpox.

Edward Jenner was a country doctor who took this story seriously. In 1796 he took material from a cowpox sore on the hand of a milkmaid named Sarah Nelmes. He put it into small cuts on the arm of a boy named James Phipps. Later he exposed the boy to smallpox. The boy did not get sick. Tests like this on a child would not be allowed today.

His method came to be called vaccination, from the Latin word vacca, meaning cow. A vaccine trains the body to fight a disease before a real attack comes. Over the next two centuries, vaccination spread worldwide. In 1980 the World Health Organization declared smallpox gone from the earth.

In the 1840s, the Vienna General Hospital in Austria had two clinics where babies were born. In one, doctors and medical students helped mothers. In the other, midwives did. Many more mothers died of a fever after birth in the doctors’ clinic. Families knew it and begged not to go there.

Dr. Ignaz Semmelweis wanted to know why. He noticed that doctors often came straight from studying the bodies of people who had died. Then a fellow doctor cut his finger during such a study and died of an illness like the mothers’ fever. Semmelweis guessed that the doctors’ hands carried something deadly.

In 1847 he made doctors wash their hands in a chlorine solution before seeing mothers. Deaths in his clinic fell sharply. Yet many doctors refused to believe him, and he could not explain what the harmful matter was. Today hand hygiene is one of the most important ways to stop infection in any hospital.

Before the 1840s, surgery was a terrible ordeal. Patients were awake. Strong helpers held them down. Surgeons worked as fast as they could, sometimes in a minute or two, because the pain was so great. Many people chose to suffer with an illness rather than face the knife.

On October 16, 1846, at Massachusetts General Hospital in Boston, a dentist named William Morton gave a patient ether vapor to breathe. The patient fell into a deep sleep. The surgeon removed a growth from his neck. When the patient woke, he said he had felt no real pain. The room where it happened is now called the Ether Dome.

This was a public demonstration of anesthesia, a way to block pain during treatment. News spread quickly to Europe. Soon chloroform was used too. Anesthesia let surgeons work slowly and carefully. Today a doctor called an anesthesiologist watches the patient’s breathing and heart the whole time.

In 1854 most people believed cholera spread through miasma, a bad smell rising from filth. John Snow thought cholera spread through dirty water. When cholera hit Soho, London, he had a chance to test his idea.

Snow marked each death on a street map. The marks crowded around the Broad Street pump. He also looked for cases that did not fit. A woman who lived far away had died, but she had the water brought from Broad Street because she liked its taste. Brewery workers nearby drank beer and mostly stayed well. These odd cases made his case stronger, not weaker.

Snow also compared two water companies in another part of London. Homes served by a company that drew water from a dirtier part of the River Thames had far more cholera deaths. The water, not the smell, was the link. Years later, other scientists found the cholera germ itself.

Snow never saw the cholera germ through a microscope. He found the cause by counting cases and looking for patterns in people, places and time. This kind of work is called epidemiology. An epidemic is an outbreak of disease that spreads to many people in an area at once.

Epidemiologists ask simple questions. Who got sick? Where did they live, work and eat? When did they get sick? What did the sick people share that the healthy people did not? The answers can point to a cause, like a pump, a food or a kind of contact.

Today disease detectives still work this way. In the United States, the Centers for Disease Control and Prevention trains people to track outbreaks, such as food poisoning from one restaurant. Like Snow, they draw maps, compare groups and share what they find so leaders can act.

In France in the 1850s and 1860s, wine and beer makers had a problem. Their drinks often went sour. They asked the chemist Louis Pasteur for help. Under a microscope he saw tiny living things, called microbes, growing in the spoiled drinks.

Pasteur found that heating the liquid gently, without boiling it, killed many of the harmful microbes. This is pasteurization, named after him. Later it was used for milk. Pasteurized milk has prevented a great deal of illness, especially in children.

Many people then believed that life could appear on its own from rotting matter. Pasteur tested this with flasks that had long curved necks. Dust and microbes from the air got stuck in the curve. The broth inside stayed clear. When he broke the neck, microbes got in and the broth spoiled. Microbes came from other microbes. This helped build germ theory: the idea that germs cause many diseases.

Rabies is a disease spread by the bite of an infected animal, such as a dog, bat or raccoon. Once signs of rabies appear, it is almost always deadly. In the 1800s, people feared mad dogs for good reason.

Pasteur’s team made a weakened form of the rabies germ from the spinal cords of infected rabbits, dried for different lengths of time. In July 1885, a mother brought her nine-year-old son, Joseph Meister, to Paris. A rabid dog had bitten him many times. The team gave him a series of shots over about ten days. He never developed rabies.

Rabies moves slowly from a bite toward the brain. That gives a vaccine time to work after the bite. This is still true today. If a person is bitten by an animal that might have rabies, doctors give shots right away. Anyone bitten by an animal should tell a trusted adult and see a doctor.

Robert Koch was a German country doctor who turned his home into a lab. He learned to grow bacteria in pure form and to stain them with dyes so they showed up clearly under a microscope. Bacteria are one-celled living things; most are harmless, but some cause disease.

In 1882 Koch announced that he had found the bacterium that causes tuberculosis, a lung disease that was then one of the leading causes of death in Europe. He announced it on March 24. That date is now World Tuberculosis Day. In 1883 and 1884, working in Egypt and India, his team identified the cholera bacterium, backing up what Snow’s maps had shown.

Koch also set out steps to prove a germ causes a disease. Find the germ in every sick person. Grow it pure. Give it to a healthy animal and see the same disease. Find the same germ again. These steps, called Koch’s postulates, turned germ theory into careful science.

Anesthesia made surgery painless, but many patients still died afterward. Their wounds filled with pus and infection. Surgeons wore old coats stiff with blood and did not wash their tools between patients. In Glasgow, Scotland, a surgeon named Joseph Lister read Pasteur’s work on microbes and had an idea.

If microbes spoiled broth, perhaps microbes also infected wounds. Lister began using carbolic acid, a chemical already used to treat sewage, to clean wounds, dressings and tools. He tried it on broken bones where the bone had pierced the skin, a kind of injury that often turned deadly.

In 1867 he reported that his patients healed far better. He called his method antiseptic surgery. An antiseptic is a chemical that kills germs on skin or wounds. Later surgeons went further with aseptic surgery: keeping germs out from the start with sterile gowns, gloves and tools.

For centuries, many doctors believed disease came from bad air or from an imbalance of body fluids. These ideas were not silly. Filthy places really did have more disease. But the true cause was usually germs living in the filth, water or food.

The change came piece by piece. Jenner showed that protection could be trained. Semmelweis showed that hands carried danger. Snow showed that water spread cholera. Pasteur showed that microbes came from other microbes. Koch proved which germ caused which disease. Lister showed that killing germs saved lives. No single person did it alone.

Germ theory changed everyday life. Cities built clean water systems and sewers. Hospitals began to scrub and sterilize. Families learned to wash hands, cook food well and keep milk cold. Much of what feels like common sense today began with these tests. Science changed its mind because the evidence was strong.

In November 1895, the German physicist Wilhelm Röntgen was testing electric current in a glass tube in a darkened room. He noticed that a screen across the room began to glow. Some unknown ray was passing through the air, and even through paper and wood. He called it the X-ray, because X stands for something unknown.

Röntgen found that the rays passed through skin and muscle but were blocked by bone. He made an image of his wife’s hand that showed her bones and her ring. Within months, doctors around the world were using X-rays to find broken bones and swallowed objects.

Early users did not know that strong doses of X-rays could harm the body. Some workers were hurt. Today radiology uses much smaller doses, and staff wear shields. Röntgen won the first Nobel Prize in Physics in 1901. X-rays opened the door to later imaging such as CT scans.

Before the 1920s, a child with type 1 diabetes usually lived only a short time. In diabetes, the body cannot control the sugar in the blood. In type 1, the pancreas, an organ near the stomach, stops making enough of a hormone called insulin. Without insulin, the body cannot use sugar for energy.

In 1921, at the University of Toronto in Canada, Frederick Banting and his student helper Charles Best took insulin from the pancreas of dogs. Chemist James Collip helped purify it, in a lab led by John Macleod. In January 1922, a fourteen-year-old boy named Leonard Thompson received insulin and grew stronger.

Insulin does not cure diabetes. It is a treatment a person needs every day. But it turned a deadly illness into one people can live with for a long, full life. Today many people with diabetes check their blood sugar and take insulin with help from their doctor and care team.

Before antibiotics, a small cut, a sore throat or an ear infection could turn deadly if bacteria spread. Doctors had few ways to stop an infection once it began. Pneumonia, a lung infection, killed many adults and children.

In 1928, Alexander Fleming found a clear ring around a mold in a dish of bacteria. The mold was a kind of Penicillium. Its juice stopped many bacteria from growing. Fleming called the substance penicillin. It was the first antibiotic of its kind: a medicine that kills bacteria or stops them from growing.

Antibiotics work on bacteria. They do not work on viruses, such as the viruses that cause colds and flu. That is why a doctor may not give antibiotics for a cold. Taking the right medicine for the right germ, as a doctor directs, matters.

For about ten years, penicillin stayed a curiosity. It was hard to make and hard to purify. Around 1939, a team at Oxford University in England, led by Howard Florey and Ernst Chain, with Norman Heatley, began to purify it and test it. In mice, it stopped deadly infections. Early patients improved.

World War II made the need urgent, because wounded soldiers often died of infection. Florey and Heatley flew to the United States in 1941 for help. At a government lab in Peoria, Illinois, scientists grew the mold in large tanks. A mold found on a cantaloupe from a Peoria market turned out to make much more penicillin.

Drug companies scaled up mass production. By the D-Day landings in 1944, large supplies were ready for Allied troops. After the war, penicillin became common for everyone. Fleming, Florey and Chain shared the Nobel Prize in 1945.

Bacteria reproduce very fast. When an antibiotic is used, most of the bacteria die. But a few may have a small change that lets them survive. Those survivors multiply. Over time, a whole population of bacteria can become hard to kill. This is antibiotic resistance.

Fleming warned about this in his Nobel lecture in 1945. He saw that using too little penicillin could help bacteria learn to resist it. Today, some infections, such as certain staph infections called MRSA, do not respond to common antibiotics. Doctors must use stronger or different medicines.

Everyone can help. Use antibiotics only when a doctor prescribes them. Take them exactly as directed. Never share them or use old leftovers. Do not expect antibiotics for a cold. Good handwashing and vaccines also help, because fewer infections mean fewer antibiotics are needed.

In the early 1950s, summer brought fear to American families. Polio, a disease caused by a virus, could weaken muscles, sometimes for life. Some people needed a machine called an iron lung to breathe. Pools and movie theaters sometimes closed. The worst year in the United States was 1952.

Jonas Salk, a scientist at the University of Pittsburgh, made a vaccine from polio virus that had been killed. In 1954, more than a million children took part in a huge test, called a field trial. On April 12, 1955, researchers announced that the vaccine was safe and worked well.

Vaccination began right away. Salk did not patent the vaccine. Later, Albert Sabin made a vaccine taken by mouth. Cases in the United States dropped quickly. Today polio has been eliminated from most of the world, and vaccination continues.

Every living cell carries instructions for how to grow and work. Those instructions are stored in DNA. By the 1950s, scientists knew DNA was important, but not what it looked like.

In London, Rosalind Franklin used X-rays to take very sharp pictures of DNA. One image, called Photo 51, showed an X-shaped pattern. Maurice Wilkins, who worked in the same lab, showed it to James Watson. In Cambridge, Watson and Francis Crick used it and other data to build a model. In 1953 they published it: a double helix, like a twisted ladder.

The shape explained how DNA copies itself. The two sides unzip, and each side builds a new partner. Watson, Crick and Wilkins received the Nobel Prize in 1962. Franklin had died in 1958, and the prize is not given after death. Many historians now stress that her work was key.

Germ theory showed that dirty water spreads disease. Cities acted on that knowledge. They built sewers to carry waste away and treated drinking water to kill germs. Adding chlorine to drinking water began in the United States in the early 1900s. Cases of typhoid, another disease spread by dirty water, fell sharply.

Chicago faced a special problem. The city took its drinking water from Lake Michigan, and its sewage flowed into the Chicago River and then into the lake. In 1900 the city opened the Sanitary and Ship Canal, which reversed the river’s flow so sewage moved away from the lake.

This kind of work is public health: protecting the health of whole communities, not just treating one patient at a time. Clean water, safe waste removal and sanitation may be the biggest life-savers of the 1900s. Many places in the world are still building these systems today.

In the early 1900s, some food sold in the United States was spoiled or mislabeled. Some medicines made false promises and did not list what was in them. In 1906 the writer Upton Sinclair published a novel, The Jungle, set in Chicago’s meatpacking plants. It described filthy conditions, and readers were shocked.

That same year, Congress passed the Pure Food and Drug Act and the Meat Inspection Act. For the first time, the national government checked meat and required truthful labels on food and medicine. This work grew into today’s Food and Drug Administration, or FDA.

Food safety also means habits at home. Pasteurized milk, refrigerators, washing hands and cooking meat all the way through help keep germs out. When people read a label, check a date or keep leftovers cold, they are using ideas that grew out of germ theory.

Life expectancy is the average number of years a newborn baby is expected to live. In the United States in 1900, it was about 47 years. By 2000, it was about 77. That is a rise of about thirty years in one century.

This does not mean most adults in 1900 died at 47. Many lived into their 60s and 70s. The average was low because so many babies and young children died of infections, such as diarrhea from dirty water or milk, measles and pneumonia. When fewer children die, the average rises a lot.

What caused the rise? Clean water, sewers and safe food came first. Then vaccines and antibiotics. Better nutrition, housing and medical care also helped. Scientists still discuss how much each one added, but most agree that public health played a very large part.