The discussion centers around identifying the top 10 emerging diseases in the U.S. and worldwide. A participant seeks definitive lists but struggles to find clear sources. The conversation touches on the classification of diseases, particularly AIDS, which is debated as an emerging disease. Some argue that AIDS does not fit the definition of an emerging disease since it has been known for decades and has not significantly declined in prevalence. Others reference recent textbooks that categorize AIDS alongside other diseases like SARS and hepatitis C as emerging due to their rising impact on health. The historical context of AIDS is discussed, noting its identification in the early 1980s and connections to earlier cases. Additionally, other diseases such as chronic active hepatitis C and non-alcoholic steatohepatitis (NASH) are mentioned as emerging concerns linked to current health trends, particularly obesity. The thread highlights the complexity of defining emerging diseases and the need for updated resources to track these health issues.