Recently we have become aware of a nasty new disease which appears to be spreading like wildfire. Authorities are somewhat taken aback by the sudden emergence and spread of the disease which is said to have begun in China. It is believed to originate in animals but when humans are infected they become highly contagious.

In spite of major efforts on the part of the medical community the looming epidemic shows no signs of abating and may yet engulf much of the world's population. One of the problems is the fact that people have become much more mobile resulting in the infection being spread from place to place.

In addition, there are rumors of sinister plots of biological warfare in which the disease is being spread on purpose to disable perceived enemies in battle. Sound familiar?

The year is 1350 A.D. and the disease is Plague. A form of Plague, first appears in China during the 14th century. From there it travels with deadly consequences through much of the known World. Before the epidemic runs its course, tens of millions of people will have died.

The Black Death, as the affliction comes to be known, begins as an outbreak in the Gobi desert in the 1320's and then quickly spreads to China proper where millions become infected and die. From there it follows the trade routes west to India, the Middle East, and Europe. At the height of the epidemic roughly 7,000 people die each day in Cairo, Egypt alone and by 1349 the plague has killed one-third of the population of the Muslim world.

Biological Warfare
In 1347 the Kipchaks, an army of Eurasian nomads are locked in mortal combat with the Genoese trading block. While laying siege to a Genoese trading post in the Crimea, they lob plague-infected corpses into the town by catapult in a deliberate attempt to spread the lethal infection. It is thought that this leads directly to the spread of the disease into Europe.

Plague is caused by the bacterium Yersina pestis and is most prevalent in rats. From there it is transmitted to human beings by infected fleas. In its most deadly form, the disease affects the lungs, and it is easily transmitted by droplets from coughing or sneezing.

Although the symptoms are soon common knowledge, at the time not much is known about the actual cause of the disease. Little can be done except to let the disease run its course. Before that happens, a large portion of the World's population will have succumbed. In Europe alone, more than 25 million die from the disease.

Van Leeuwenhoek and his magic glass
Before the true cause of this and many other diseases becomes known, we have to wait for a Dutch haberdasher and sometime lens maker, Antoni Van Leeuwenhoek. In 1677 using a crude lens, he discovers what he calls animalcules in pond water. Later these would be recognized as bacteria, the source of many human afflictions.

As a result of his discoveries, Van Leeuwenhoek early on concluded that the notable thinkers of his day had got it wrong. They believed in a kind of spontaneous generation in which maggots erupted from putrefied matter, weevils and fleas from wheat grains and small sea creatures from sand particles. It was obvious to him that these all originated from tiny eggs instead, as revealed by his "microscope".

Van Leuwenhoek also describes three different types of bacteria: bacilli, cocci, and spirilla. Bacilli are rod-shaped, cocci are spherical and spirilla are yes, little spirals. As important as these discoveries are, more pieces of the puzzle have yet to be found. For the next several hundred years most people continue to believe in spontaneous generation and no one it seems, makes the connection between Van Leuwenhoek's animalcules and disease.

The Microbe Hunters
For that we turn to that well-known French scientist, Louis Pasteur. Pasteur was born in Dôle, France on December 27, 1822. The son of a tanner, he grew up in the small town of Arbois. In 1847 he earned a doctorate at the École Normale in Paris.

Much of his early work related to that oh so French enterprise, wine making and more specifically why the stuff went sour. He was able to confirm that yeast produced the good effect of fermentation but that other micro-organisms such as bacteria made wine go sour, a bad thing. His solution for eliminating the bacteria was to heat the starting sugar solutions to a high temperature before adding the yeast. Can everybody say "pasteurize"?

By 1860, as he continued to experiment, he was able to establish once and for all that bacteria, like all living organisms, arise only from other similar organisms and not spontaneously. Not everyone was convinced but his ideas prevailed. He also discovered that many infectious diseases are caused by bacteria. At about the same time in 1876 Robert Koch, a German scientist and early Nobel laureate came up with an idea for studying bacteria outside a host patient. Koch, arguably one of the more important pioneers in the field of Micro-biology, was born in Klausthal-Zellerfeld, Germany, on December 11, 1843.

Along with British surgeon Joseph Lister, he developed the techniques for growing cultures of single organisms in a dish. This made it possible to associate specific bacteria with specific diseases. With this little breakthrough he was able to prove that a bacterium was the cause of Anthrax. He also isolated several other disease-causing bacteria, including those of tuberculosis.

Meanwhile in 1880, Pasteur discovered quite by accident that cultivating Anthrax bacteria at higher temperatures rendered them less potent. Then, when these "weakened" bacteria where introduced into healthy animals they developed an immunity to the real thing. Today we call this immunization.

Those Pesky Viruses
Also in the 19th Century the idea of viruses was first suggested initially by Jacob Henle who taught Robert Koch. Already in the 1840's, Henle suggested that there were infectious agents too small to be seen with a microscope. Because he couldn't prove it his idea did not go much of anywhere at the time.

In fact, Pasteur who in 1885 was trying to develop a rabies vaccine was not aware that rabies was caused by a virus. In spite of this he created a successful vaccine because both bacteria and viruses create similar immune responses in the body. All the same, viruses are a different type of organism.

While the study of bacteria became almost routine thanks to the Koch-Lister methods, no one had actually ever seen a virus. Methods used to isolate bacteria were completely ineffective with viruses. Without going into too much detail, viruses in addition to being a totally different agent from bacteria are also much much smaller.

This meant that you couldn't see them under the microscopes of the day. It also meant you couldn't filter them out using the available filters. This didn't prevent some experimenters from demonstrating that this unseen agent was able to transmit disease. By 1880, a German scientist Adolf Mayer was able to do just that.

This effort along with that of a colleague, a Dutch scientist Martinus Beijerinck demonstrated, that an agent that was not blocked by any filter could in fact still pass on a disease. In 1898, Beijerinck also showed that this substance was able to grow and reproduce in the cells of the host tissue suggesting it was an actual organism.

It wasn't until 1935 that a virus was actually identified and by 1939 a virus could be seen for the first time using the newly developed electron microscope. And so we have come a long way since the Plague swept through most of the known World... or have we.

Viruses versus Bacteria
As we have seen, disease can be caused by either bacteria or viruses. What's the difference. There are in fact many, too many to list here. Also most bacteria and viruses while not all necessarily beneficial, do not cause disease. With those that do, the differences become significant.

A major difference relates to size. A second important difference has to do with how successfully they reproduce or multiply outside a host. This leads directly to a third difference, our success in killing either organism inside the body. Because bacteria can be readily cultured in the laboratory, finding agents to kill them off is a relatively simple task.

Simply put, all one has to do with bacteria is to expose them to any of a multitude of toxic agents and watch the results. If it can be shown that the effective agent is also relatively harmless to the host, meaning you and me, you've got yourself an anti-biotic. It may not be quite that simple but you get the idea.

Finding an anti-viral agent is much harder and a lot of that has to do with successfully growing a virus outside the host. It is not an easy task and as a result most of the success in treating viral disorders relates to prevention or immunization. Pasteur discovered early on that a weakened or even dead version of a bacteria or virus can prevent disease.

Introducing these weakened or dead organisms or agents into a potential host like you or me, can confer an immunity to a number of diseases normally caused by the agent. We are familiar with many of these such as Smallpox, Measles, Mumps, Rubella, Influenza, Croup and of course the Common Cold. Of these only the Common Cold has defied our efforts at a vaccine.

There are also a number of diseases that can be caused by either a bacterium or a virus. These include Pneumonia and Meningitis. In addition to vaccination, most bacterial infections can also be helped by the judicial application of an antibiotic. These include the grand-daddy of them all Penicillin as well as many of the newer agents that have proven effective against bacterial infections.

However, other than vaccination, there is little to be done about viral infections. In most cases we must rely on the body's own immune system to successfully overcome these intrusions. Vaccines can help us in this struggle but often our immune system is left to fend for itself.

Much work is being done with anti-viral agents which has been met with some limited success. However the results are far from consistent. Also in recent years, not all bacterial infections can be successfully treated with antibiotics.

Introducing the Super Bugs
One of the worrying aspects of disease in the 21st century is the emergence of "super bugs". Although there have been alarm bells ringing for nearly forty years, only now is this problem receiving some attention. Super bugs are "ordinary" bacteria that have become much more virulent and resistant to most antibiotics. The cause is simple enough.

Whenever any group of living organisms is being eradicated there are inevitably a few who escape. In the case of bacteria this is probably because a few in the group have more resistance to the anti-bacterial agent than the rest of their peers. These survivors are dangerous because they survived.

As these few superior specimens reproduce they are likely to pass on their resistance to their offspring. When this group is next attacked there is once again a similar weeding-out process that will lead to the survival of the fittest. Not only do we now have a slightly larger group, but their ruggedness has been even more finely honed.

So why has this happened? There are several causes. First of all in the past antibiotics were too often inappropriately prescribed for purely viral infections. Not only would they be ineffective but as a unintended side effect the few bacteria that happened to be in the host at the time would be effectively screened for survivors.

Also, in spite of the constant warnings to all users of prescription drugs to completely finish any prescription, many people disregard this advice and stop taking the drug as soon as they feel better. This practice results in the screening for the fittest bacteria to survive. They will return to fight another day.

In addition there have over the years been many instances in some jurisdictions where antibiotics are not closely monitored, of some people medicating themselves as a preventive measure. This practice was and possibly is especially prevalent among prostitutes and others in high risk situations. This once again results in the survival of tougher, smarter and much more dangerous bacteria.

In a very questionable application of antibiotics, there is a very prevalent practice among farmers to liberally dose their livestock with these drugs. No doubt some of this is to prevent or cure infections but the main reason is to improve the growth and output of their stock. An ill-conceived method of increasing production to be sure.

There is an additional side issue of the addition of hormones to livestock for the same reason. Beside the obvious risk of creating ever stronger bacteria there is the additional effect down the food chain of subjecting unwitting consumers to significant amounts of all these agents.

The Current Situation
As we cower before a significant new threat to our well-being, the rather sudden outbreak of what appears to be a whole new disease, what are we to think. It would probably make sense to gain a bit of insight into the whole issue of the Severe Acute Respiratory Syndrome, or SARS.

There is little doubt that this "new" disease probably originated in livestock, likely a species of pig routinely raised on farms in China. In other words it appears to have jumped the "species barrier" from animal to man. Although this phenomenon is far from common, it is by no means unique.

Diseases that routinely infect both animals and man are called Zoonoses or Zoonotic Diseases. Some of the better-known ones include Rabies, Hantavirus infections, Lyme disease, Viral Hemorrhagic fevers such as Crimean-Congo, Ebola, Lassa and Marburg viruses, and so the list goes on.

Many of these are viral infections which means we don't really have a cure. Our ultimate defense is an effective vaccine and our attempts to create one are not always successful. Our only other hope is a vigilant and well fortified immune system.

The Prognosis
The best evidence suggests that S.A.R.S. is caused by a virus. The agent is most likely a new (mutated?) coronavirus so called because of its crown-like appearance in electron microscope imagery.

Until now, coronaviruses were believed to produce only minor illnesses in people, like colds, diarrhea and other intestinal disorders. In animals however, coronaviruses can cause severe and often fatal illnesses. This certainly points to a species barrier jump.

What is puzzling is the fact that having infected humans it is able to thrive and spread so effortlessly. Droplets expelled into the air by coughing and sneezing is generally blamed but the speed with which the infection spread in at least one Hong Kong housing complex has researchers searching for other answers.

The most urgent and do-able next step is to devise a screening tool to confirm the presence of the disease in a patient. Without this you can't identify who is infected and who isn't. Many people are being unecessarily quarantined because of this. It also adds to the hype and anxiety. Once we have a screening tool the next step would be a vaccine. Time will tell how successful we will be.

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