Emerging Diseases: A Cause for Panic or a Time for Science?

man stands with arms crossed and smiles

Peter Hudson

"You know the scenario," said Peter Hudson. "There you are, minding your own business, when suddenly somebody comes up behind you and 'Aaa-choo!'... Somebody spreads you with viruses."

Viruses and other infectious diseases were the focus of last Wednesday's Research Unplugged event. Hudson, the director of the Huck Institutes of Life Sciences at Penn State, drew a large audience to the lobby of the Penn State Downtown Theatre for a fascinating—and at times, even wryly humorous—discussion of emerging diseases around the globe.

Hudson opened the discussion by hearkening back to 1969, when then-U.S. Surgeon General Bill Stewart issued the statement, "It's time to close the book on infectious diseases."

Stewart was wrong, Hudson said. Although we have wiped out some diseases, like smallpox and polio, we have a long way to go. "It looks as though, with vaccines and antibiotics, we can squash these diseases," he noted. "Yet there are about 1,405 infectious agents that affect humans, and there are only vaccines against 23 diseases." What's more, he explained, "there are six diseases which cause 90 percent of deaths attributed to infections. Those are respiratory diseases, HIV, diarrheal diseases, tuberculosis, malaria, and measles."

"We have the world's leading group on measles here at Penn State," Hudson noted. "They are working on how to apply vaccines in Nigeria where it's a major cause of death in children."

"Historically we know that diseases have been immensely important," Hudson stated, reminding the audience of the destructive power of pandemic infections. "The bubonic plague alone reduced European population by 25 percent. It took Italy more than 400 years to recover from that one epidemic."

"In 1918, 20 million people died from influenza," Hudson continued. "More people died of flu that year than died in the first World War."

One key to a virus's ability to spread quickly in a population might be found by studying "super-spreaders," said Hudson. A super-spreader is the rare individual who is highly-infectious yet asymptomatic, and whose behavior exposes large numbers of people to the virus they carry.

For example, Gaetan Dugas, a French Canadian flight attendant, is thought to be among the first few people to introduce HIV infection into North America. What made Dugas significant, explained Hudson, is that he was asymptomatic for a long time, may not have understood the infectious nature of his disease, had many sexual partners, and traveled widely due to his profession. Dugas "was linked to 40 of the original patients that died from AIDS," before his own AIDS-related death in 1984.

Noted Hudson, America's most famous example of a super-spreader may be Mary Mallon, notorious as "Typhoid Mary" in turn-of-the-century New York. Mary Mallon is said to have initiated 28 outbreaks of typhus. "She was a cook, and she did not have very clean toilet habits, and probably didn't wash her hands," Hudson said. "Everywhere she went, people started getting ill, so she would sneak away to somewhere else." Mallon may have infected 1,400 people in Ithaca, N.Y. alone.

More study is needed to understand why super-spreaders don't get sick themselves, Hudson commented, adding that having a lot of mucus and an innate immune response helps keep away many viruses and diseases.

Hudson enumerated several issues of current concern regarding emerging diseases. "Our big scare is biosecurity. When will H5N1 ('bird flu') come?" he asked. "We don't know because we have no data; we haven't followed this before. We can only make educated guesses." He also touched on practical challenges related to production of the vaccine and ethical questions regarding who to vaccinate if supply is limited.

"We have a real problem trying to predict when the next disease will come," Hudson continued. For example, he noted, SARS was one virus whose emergence was completely unexpected. Hudson said it is believed that the SARS virus originally came from bats, which infected palm civets, cat-sized mammals common in Southeast Asia. The palm civets were then sold in markets in China, where people ate the tainted meat, he explained.

There are also disease and conservation issues. "The much bigger problem at the moment is where the gorillas are really being hammered by Ebola," he explained. "Gorillas could well be wiped out." Other issues, he continued, are antibiotic resistance and the influence of climate change.

Hudson concluded by telling the audience that researchers at Penn State are bringing together different disciplines in a novel effort to learn about infectious diseases. "We are trying to reach back into the physical sciences, particularly statistics, physics, math and computation," he explained. "The approaches that they take are immensely important to be able to make predictions in the future. If we can do that, we can start to reach forward into many of these issues."

Peter Hudson, Ph.D., is Willamna professor of biology in the Eberly College of Science and director of the Huck Institutes of Life Sciences. He can be reached at pjh18@psu.edu.

Last Updated October 22, 2007