Coughs, Sneezes and Diseases

A Little History Of Science: Coughs, Sneezes and Diseases

If we have a runny nose, a cough or a stomach upset, we often say we have caught a bug or a virus, by which we mean some kind of germ. The notion of ‘catching’ something is so natural to us that it is hard to realise how amazing it was when someone came up with a theory that diseases can be caused by germs. Centuries before, doctors had explained that the ills people suffered were due to internal changes in the humours. Even more recently, doctors knew they could blame a bad constitution (we might say ‘bad genes’), or too much indulgence in food or drink, or bad habits such as staying up all night. No one had thought that a living organism from the outside could cause a disease. It was a new idea, and it led to a major re-think about what disease itself actually means.

Doctors in earlier times had certainly talked about the ‘seeds’ of disease. The word ‘virus’ was often used too, but it then meant simply ‘poison’. People dying from poison, accidental or deliberate, was nothing new. What was new with this theory of germs was that the external source was a tiny, living creature – a micro-organism. It brought with it a language of warfare: the body had ‘defences’ against this germ, and could ‘fight’ infection. Germ theory was a great turning point in medicine.

We met its most important champion, Louis Pasteur, in the last chapter. He came to germs gradually. He had been busy investigating the role of micro-organisms in many everyday events: the brewing of beer, the fermentation of wine, the baking of bread. The ‘pasteurisation’ of milk and other dairy products came to rely on discoveries he made: look in your refrigerator and you will see his name used. Pasteurised milk has been heated to just the right temperature, which kills the ‘germs’ in it. It will last longer and be safer to drink.

It was still a big step to show that bacteria, yeast, fungi and other micro-organisms could cause human and animal diseases. It was one thing to see these micro-organisms through a microscope, another thing to show that they and nothing else caused a particular disease. What we now call infectious diseases have always been killers. The bubonic plague, or Black Death, caused high fevers and very painful swellings on the body, known as buboes. It repeatedly swept through British towns and cities for more than 300 years from the 1340s onward. It was spread by fleas that lived on black rats, but moved on to humans when the rats died of plague, too. Smallpox, typhus, scarlet fever, with their skin rashes and high fevers, also took their grim toll. Parents might have eight or more babies and lose most of them to disease while they were still children.

When doctors studied these diseases, they explained them in one of two ways. Some thought these diseases of whole communities were contagious. That means they were spread from person to person by contact: when a healthy person touched a sick person or a sick person’s clothes or sheets. Smallpox, with its horrible spots, seemed to be a contagious disease, especially since people who had not had the disease often came down with it if they nursed a friend or relative.

The spread of other diseases was much less easy to explain by contagion. Doctors had a theory that these diseases were caused by ‘miasmas’. A miasma is a foul or unhealthy smell or vapour.

Miasmatic diseases happened, they said, because of unhealthy disturbances in the atmosphere: the stench of rotting vegetation and sewage, the bad odours of the sickroom. During the 1800s, cholera was the most feared epidemic disease. It was common in India but in the 1820s it began to spread around the rest of the world. It took six years to travel from India to Britain, where it caused panic because it was a new and very frightening experience.

Cholera caused dramatic diarrhoea and vomiting, leaving the poor victim shrivelled and in agony, dying an undignified death. It often killed in a day. Today, international travel helps disease spread very quickly. In those days it made a slower progress. As European doctors and officials watched cholera spread slowly over Asia and Eastern Europe, they could not decide whether it was spreading from person to person (by contagion), or whether this was a miasmatic epidemic.

Many people were worried that the disease was spreading through something everyone shared: the air they breathed. Depending on which theory they believed, officials could do different things to try to stop disease spreading. If contagion was the cause, then it was best to isolate and quarantine the sufferers.

For miasma, cleaning up and improving air quality were important. It was cholera that triggered the most intense debate when it first struck Britain in late 1831. In the panic, medical opinion was divided, but the quarantine measures did not seem to do much good. When the disease came again in 1848 and 1854, a London doctor, John Snow (1813–58), brilliantly worked out what was happening. By talking to local residents, and carefully mapping out each individual case in the neighbourhood, he became sure that the cholera was being spread by water from a public pump in Soho, central London. He believed it was contaminated with the faeces and vomit of cholera victims, and took a sample to examine by microscope. Although he could not identify any specific cause, his work emphasised that clean water was needed for public health.

Snow’s research had shown how cholera was spread, not what caused it. For that, the laboratory was crucial, and especially the laboratory of Louis Pasteur. As he continued his research on micro-organisms, the French government asked him to investigate a silkworm disease that was destroying the French silk industry.

Pasteur dutifully moved with his family to the south of France, where silk was being produced. He put his wife and children to work with him on trying to identify the cause of the problem. It turned out to be a micro-organism that was infecting the silkworm larvae. By showing how it could be avoided, Pasteur saved the French silk industry. This put Pasteur on the disease trail. He wanted to demonstrate his belief that micro-organisms cause many of the diseases from which human beings and animals suffer. He began with anthrax, a disease of farm animals that was sometimes passed to humans.

Until recently, this disease was largely forgotten, although it’s one that terrorists now threaten us with. It causes nasty sores of the skin and, if it spreads to the bloodstream, it can kill. It is caused by a large bacterium, so it is relatively easy to detect. Anthrax was to become the first human disease Pasteur was able to prevent by making a vaccine.

Back in 1796, Edward Jenner (1749–1823), an English country doctor, had found a way to prevent smallpox by deliberately injecting a boy with cowpox, a similar but much milder disease. Cowpox was a disease of cows that milkmaids sometimes got, and it had been observed that these girls seemed to be protected from the more dangerous smallpox. Jenner called his new procedure vaccination (from the Latin word for cow, vacca), and vaccination programmes were started in many countries. They helped make this serious disease much less common.

Pasteur wanted to do something similar for anthrax, but there was no closely related disease around. Instead, he learned how to make the anthrax bacterium weaker, by changing its living conditions, such as the temperature, altering the food it could use, or exposing it to the air. Bacteria need the right conditions to flourish, just as we do. Pasteur succeeded in making his anthrax bacteria much less able to cause disease, and he called these weakened bacteria a vaccine, in honour of Jenner. Then he invited newspaper reporters to witness an experiment. Having injected some sheep and cattle with his vaccine, he gave the anthrax bacteria to that group, and to another. The experiment was an outstanding success: the animals he had vaccinated were unaffected when given the bacteria, whereas the unprotected animals died of the disease.

Pasteur had made the world conscious of the power of medical science. After anthrax came rabies. Rabies is a horrible disease, generally caused by a bite from an infected animal. It is often fatal, and its victims – including many young children – foam at the mouth and can’t even drink water. The remarkable thing about Pasteur and rabies is that he could not even see what he was dealing with. The virus that causes rabies is so small that the microscopes available to Pasteur and his contemporaries could not bring it into focus.

However, Pasteur knew from the victims’ symptoms that whatever was causing rabies was attacking the brain and spinal cord, at the centre of the nervous system. So he used the spinal cord of rabbits to ‘culture’ (grow) the virus artificially. He could make it more, or less, harmful, according to the conditions under which he cultured it. He used his weaker virus to make a vaccine. His first human case was a dramatic success and made Pasteur a worldwide name.

Joseph Meister was a young boy who had been bitten by a rabid dog. His desperate parents brought him to Pasteur, who agreed to try to save his life by a series of injections. Pasteur was a chemist, so a doctor actually had to give the injections, but the vaccination was a triumph. Young Meister survived, and worked for Pasteur for the rest of his life. Other people bitten by rabid animals hurried to Paris to receive this new miracle cure. The successful treatment created an international sensation, and people donated money to start a Pasteur Institute, where Pasteur worked until he died. The Institute is still going strong, more than a century later.

Pasteur was always unusual, both in his outstanding successes and in the ways he grew and studied his micro-organisms. Other scientists found his methods clumsy and difficult. Many of the laboratory tools that scientists still use to study bacteria were developed by Pasteur’s German rival, Robert Koch (1843–1910). Unlike Pasteur, Koch was a doctor, who began his work while treating patients. He, too, worked on anthrax, that bacterium that was easy to see. He worked out how anthrax moves from animals to humans and discovered that it has a complicated life-cycle.

Sometimes the anthrax bacteria go into a kind of hibernation, known as the ‘spore phase’. These spores are very hard to kill and they too can infect humans and animals so that they develop the disease in more than one way. Even though bacteria consist of only one cell, it turns out they are very complicated organisms. Koch pioneered the use of photography to make a visible record of bacteria that cause disease. He grew his bacteria on a solid kind of jelly called agar-agar: this allowed individual ‘colonies’ (groups of bacteria) to be identified and studied. It was much less messy than Pasteur’s flasks and soups. One of Koch’s assistants, named Petri, invented the little dish used to hold the agar and grow the bacteria.

Koch also appreciated the use of coloured stains to help identify different bacteria. These developments changed the face of bacteriology, and helped the international group of doctors and scientists begin to make sense of these tiny organisms.

Koch was a ‘microbe hunter’. (‘Microbe’ is just short for micro- organism.) He identified the germs that caused two of the most important diseases of the nineteenth century. In 1882, he announced his discovery of the tubercle bacillus, the bacterium that causes tuberculosis. Tuberculosis killed more people than any other disease in the nineteenth century, but doctors thought it was either inherited, or the result of an unhealthy lifestyle. Koch’s research showed that tuberculosis is an infectious disease, spread from a sick individual to another person. It differed from other epidemic diseases such as influenza, measles, typhus and cholera, because it is a slow disease – slow to spread and infect, and slow to kill.
Tuberculosis usually destroys the lungs over a number of years.

Koch’s second great find was the bacterium that causes cholera, that other most feared disease. When it appeared in 1883 in Egypt, the French and the Germans sent scientists to see if they could uncover its cause. It was a kind of competition. One of the French team caught the disease and died. (Pasteur had wanted to go but was too frail.) Koch and his German colleagues thought they might have found the right germ, but they could not be sure. So Koch went on to India, where cholera was then always present. In identifying the cholera bacillus, he showed that Snow had been right – it was something in the water after all. He found the bacillus both in the diarrhoea of its victims, and in the wells from which they drew their water. Understanding the cause of infectious diseases paved the way for better control and, eventually, for vaccines, which have saved countless millions of lives over the past century.

From the late 1870s, many disease-causing germs were correctly identified (and many were announced that were later shown not to be dangerous at all). It was an exciting period, and a lot of doctors thought it heralded a new dawn for medicine and hygiene. It showed the importance of clean water, milk and everything else we eat and drink. From then on, doctors have advised us to wash our hands after using the toilet, and to cover our mouth when we cough. Identifying germs meant that scientists could make vaccines and, later, drugs. And it made modern surgery possible.

As early as the 1860s, the English surgeon Joseph Lister (1827– 1912) had been inspired by Pasteur’s germs. He introduced what he called antiseptic surgery. You probably have some antiseptic cream in your first aid kit. Lister’s new method involved carbolic acid, also known as phenol, which was used to disinfect sewage. He would use carbolic acid to wash his surgical instruments and the bandages he would put over the body where it had been cut. He later invented a device to spray carbolic acid over the patient’s body and the surgeon’s hands during the operation. When Lister compared his patients with those of surgeons not using his ‘Listerian’ methods, or with his own pre-Listerian patients, he found that many more had survived their operation. They had not died from infections that started at the site of the operation and spread in the blood. In his experiments to disprove spontaneous generation, Pasteur had shown that ‘germs’ were carried through the air on particles of dust.

Lister was killing these germs with his carbolic acid routine. Just as he had improved on Pasteur’s laboratory tools, so Robert Koch would advance Lister’s antiseptic surgery. Lister had aimed to kill any disease-causing germs in the wound. Koch’s aseptic surgery would prevent them getting into the wound in the first place. Koch invented the autoclave, a device that used very hot steam to sterilise surgical instruments. Aseptic surgery allowed surgeons to safely enter the body cavities (the chest, abdomen and brain) for the first time. It gradually brought about our modern operating theatre, with its surgical gowns and masks, rubber gloves and sterile equipment.

Along with modern hygiene, surgery could not have advanced without anaesthesia. It had been introduced into medicine in the 1840s, in America. Anaesthesia was a triumph for chemistry in the service of medicine, since the compounds that were shown to put people to sleep – ether and chloroform – were chemicals made in the laboratory. (Humphry Davy’s nitrous oxide was another early anaesthetic.) The removal of agonising pain, and sometimes death, from surgery and childbirth seemed nothing short of miraculous.

One of its British pioneers was John Snow, of cholera fame. Snow’s anaesthetic career peaked when he gave anaesthesia to Queen Victoria, during the birth of her last two children. The Queen, who had had seven babies already without anaesthesia, thought it was a jolly good thing. Understanding germs helped make advanced surgery possible.

It also offered doctors ways to understand the infectious diseases which had caused so much pain and death throughout human history. There was now a scientific basis for Edward Jenner’s discovery of vaccination to protect against specific diseases. These injections are worth it, even if they hurt at the time, for they offer hope that if everyone is vaccinated, many infectious diseases can be conquered. We know a lot more about germs than at the time of Pasteur and Koch. And we are more aware, as Chapter 36 will tell, how adaptable and slippery they are, these bacteria, viruses and parasites. They have been able to adapt to the medicines and treatments that doctors aim at them, and to become resistant – a lesson in Darwinian evolution. They survive because they adapt, a lesson that Darwin first taught.