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May Term Class: Plagues

Historical Plagues and Emerging Diseases


Taught by Associate Professor of Biology Lawrence Anderson

Plagues --- They've changed the course of history; stopping conquerors, decimating entire populations, causing economic collapse of empires, and serving as an early form of biological warfare used by the British when they gave smallpox-tainted blankets to Native Americans. It's around the ancient plagues, some of which still exist today, that Professor Lawrence Anderson designed the May term course "Historical Plagues."

Anderson points out that overcrowding often gave plagues a dramatic edge. Walled-up cities facilitated easy transmission from person to person, as did other close-quartered environments such as ships. In the 19th century during the Irish potato famine, when the starving loaded onto overcrowded ships to come to the New World, Rickettsia prowazekii (typhus), which is transmitted by lice, found plenty of hosts. Thousands died on board or at North American sites of disembarkation.

Today, we worry about catching a virus or bacterial infection on planes. It wasn't so different with the bubonic plague, which was clearly linked to the old trade routes. "Those routes that had developed over the previous centuries were pivotal in giving those infestations a pathway," said Anderson.

The bubonic plague (Yersinia pestis), which in the 14th century decimated populations throughout Europe and Asia, is still around today. "It's a difficult pathogen to eliminate because it is carried by animals and can be transmitted to humans by fleas. There are still a few cases every year in the western United States and other parts of the world. These cases are often misdiagnosed, though we know a lot about the bacteria molecularly. With the correct diagnosis, the bubonic plague can now be treated with an antibiotic," said Anderson.

In explaining the role of antibiotics, Anderson stated that the bacterial ribosome, site of protein synthesis, differs from the human ribosome. "Many of the antibiotics we use today bind to the bacterial ribosome and inhibit protein synthesis, while not affecting human ribosomes. Another example is that bacteria have cell walls around them and these walls are not in humans. Agents such as penicillin inhibit the synthesis of cell wall materials without harming human cells," he said, thus rendering the bacteria harmless.

But as Anderson points out, viruses present a more difficult problem because they use the host cell for replication. Therefore, anything toxic for the virus would also be toxic for the host cell. So you need something virus specific that will inhibit the virus without damaging the host cell. "If you have a good vaccine, then ultimately the virus has no host and disappears," said Anderson.

Anderson explained that during the American Revolution, when the smallpox virus was present in the colonies, the British were already naturally immune or, if not, would take a bit of puscular material, scratch it on the skin, and in most cases produce immunity. The Americans were mostly non-immune and therefore suffered greatly from smallpox--until George Washington ordered vaccinations for the Americans. This one step may have saved the American Revolution.

According to Anderson, the history of the great plagues can teach us a lot. Today, researchers may go to gravesites to recover nucleic acids of the pathogens from those who died, such as the 1918 Spanish flu (influenza), to learn more about these pathogens and why they were so virulent. Other clues sometimes lie in historical literature.

In his history of the Peloponnesian War, Thucydides described the Great Plague of Athens and its symptoms. "This account of the plague gives us some clues," said Anderson, "but we can't match it perfectly to any known agent in the current age. The cause of this outbreak is still an enigma."

Many of the emerging diseases today, such as HIV or SARS, are viruses, and Anderson teaches a separate May term course focusing on that topic. Designed for science majors, the course examines the biochemistry of the microbes.

May term classes are month-long courses, unique to Westminster. These classes challenge the faculty to find innovative ways to teach.