Students should be aware of serious diseases, such as yellow fever, HIV, AIDS and the Ebola virus that affect the world today, said Thomas Yuill in a Global Awareness Lecture Wednesday, Feb. 7, 2007.

Yuill, emeritus director and professor of the Gaylord Nelson Institute for Environmental Studies, said in a lecture "Emerging Diseases in the Tropics" that there are three main things that students should remember. The first is that disease-causing organisms are part of the ecosystem. The second point is that humans are part of the ecosystem, and the third is that ecosystems change rapidly.

Human activity drives changes in the ecosystem, which is causing many of the diseases today, Yuill said.

"We are causing one of the greatest mass extinctions in the history of the planet," Yuill said. "These things have consequences."

There are six types of causal situations that explain the impact of diseases on the world today, Yuill said. The first is catastrophic diseases that have faded into the background but still have an impact on the world today. Yellow fever, which is transmitted by a mosquito and is a problem in the tropics and Africa, is one example of this.

"This mosquito is all over the tropics," Yuill said. "It's a very efficient vector for yellow fever. There's a potential for rapid spread."

The second type of situation is new diseases that have been alive all along. These diseases include Ebola hemorrhagic fever, which has been an epidemic in the Democratic Republic of Congo.

"It's one of the more ghastly diseases today," Yuill said.

Cultural practices in the Congo, such as washing the body of the dead, even if it is covered in virus-infested blood, helped spread the Ebola disease, Yuill said. He also said it is difficult to change cultural practices, especially in rural areas where people do not understand that germs can cause diseases.

The third situation is ecosystem management. This is when humans create unexpected consequences when they change the environment. One example of this is Rift Valley Fever, which is a problem in West Africa that was created when humans attempted to control the flow of water. The areas receiving increased water also received more mosquitoes that brought the Rift Valley Fever.

The fourth situation is old diseases that move to new areas. One example of this today is Dengue Fever, which has spread from Southeastern Asia.

"It used to not be in the western hemisphere," Yuill said. "Now there's Dengue, Dengue all over the place."

The fifth situation is boring old diseases that become hot topics. The bubonic plague killed 25 percent of the world population in the 1300s, but it is still a problem in some parts of the world, Yuill said.

The final situation is that truly new diseases do appear. HIV and AIDS are diseases that have appeared that have huge economic costs.

There are certain things that we can do to solve these problems. Assessing the problem is first, Yuill said. Intervention that is both epidemiologically sound and affordable is also necessary. An integrated system that includes a follow-up to assess if the problem has been solved is also crucial, Yuill said.

"Come back in 30 years and we'll see what the new diseases are," Yuill said.



Copyright Brigham Young University 7 Feb 2007