Tom D. Y. Chin, MD. MPH

I am Professor Emeritus of Preventive Medicine and of Medicine at the University of Kansas Medical Center. My entire career has focused on infectious disease epidemiology. Respiratory virus infections have been one of my research interests for many years.

 My first professional exposure to influenza was in July1957 when I was asked by Dr. Alex Langmuir of CDC to investigate an outbreak of influenza at Grinnell, Iowa, where a religious conference was being held. Cases of influenza suddenly appeared shortly after arrival of the participants by train from California. This outbreak was the source from which influenza spread to various parts of the United States by the participants returning to their homes. A number of outbreaks occurring in different parts of the United States were traced to the infected participants. During that winter my CDC colleagues and I investigated an epidemic of Asian flu in Southwest High School in Kansas City, Missouri. The investigation yielded some very important data on how the virus had affected the students and their families. When Hong Kong influenza hit the Kansas City Metropolitan Area again during the winter of 1968, we decided to do a study in the same high school. These studies had provided us an opportunity to compare the epidemiological characteristics of the two pandemics of influenza occurring 11 years apart. 

Among the viral respiratory infections, I consider influenza most intriguing. It has caused major pandemics from time to time, probably as early as 1510, and between pandemics, the virus tends to mutate every 2-3 years to cause epidemics. The pandemic of 1918 was most devastating, killing over 20 million people. 

In this presentation, I intend to give a rather broad overview of influenza, emphasizing the epidemiological features. Why is pandemic influenza so unpredictable? What causes emergence of new influenza viruses? Is influenza a zoonosis? . 

It appears that aquatic birds are the primary reservoir hosts of influenza viruses in nature, and pigs appear to be intermediate hosts. Presumably, new human influenza viruses emerge as a result of mixing the gene fragments of two influenza viruses in pigs. Exactly how these newly emerged viruses become human pathogens and cause widespread epidemics is still a mystery. Much remains to be learned. I hope this presentation will kindle your imagination as much as it has on me.