Germ Theory, Parts I and II

Yesterday, we learned about this year's flu bugs and saw the worst flu ever. Today, we're taking a closer look at germs--those malevolent little microbes that make us sick.

The idea that disease is caused by invading microbes is really rather new. It wasn't until the mid-19th century that scientists learned that "germs" could multiply inside your body and make trouble. And it wasn't until far more recently that they learned just how various that trouble can be.

Germ Theory, Part I

In 1864, the French scientist Louis Pasteur--who succeeded in developing vaccines for anthrax and rabies--concluded that some really bad microbugs can live in the air. By 1882, Robert Koch, a German, had extended Pasteur's observation into a discovery of huge medical significance. Koch proved that tuberculosis, a scourge of the 19th century, was transmitted through a specific type of airborne bacteria.

Koch's discovery--that specific diseases are caused by specific pathogens--revolutionized medicine. He famously outlined four postulates for linking a dangerous microorganism to a given disease:

1. The microorganism can be found in the diseased animal.

2. The microorganism can be isolated from the diseased animal and grown in the lab.

3. The cultured microorganism will cause the disease when put in a healthy susceptible animal.

4. The same microorganism can be isolated from the newly infected animal.

With a few provisos, Koch's postulates still stand as a way to determine whether a specific microbe causes a given disease. For the first time in medical history, doctors had a scientifically valid "germ theory" they could use to investigate disease in the lab and diagnose people in the world.

And Now, Part II

But doctors aren't resting on their laurels. Today, some scientists believe that many diseases we now attribute to myriad causes--such as cancer and heart disease--may actually be caused by pathogens. It's "germ theory, part II," and research on stomach ulcers has paved the way for its broader acceptance.

For years, doctors blamed stomach ulcers on spicy diet, aspirin irritation, or stress. But in 1982, Australian doctors Barry Marshall and J. Robin Warren discovered that when ulcer patients with stomachs full of spiral bacteria (Helicobacter pylori) were given antibiotics, their stomach pains and ulcers disappeared.

At first, the clinical community ignored their research. So Marshall took extreme measures. In 1985, he swallowed a cocktail of spiral bacteria and proved that the bacteria do cause stomach ulcers. With antibiotics, up to 90 percent of stomach ulcers can be tamed. Even better, a simple breath test can detect the pathogen.

This kind of evidence has some doctors believing that diseases we attribute to genes or the environment are really caused by germs. For example, patients with coronary heart disease tend to have a lot of antibodies to the bacteria Chlamydia pneumoniae. Does that suggest heart patients may be battling an infection that triggered inflammation, plaque, and ultimately arterial blockage? Some doctors think so--and say that, one day, we'll pin heart attacks on a germ.