Why has the germ theory changed over time?

The germ theory has evolved due to advances in technology and scientific understanding, particularly in microbiology and genetics. Initially, it established that microorganisms cause many diseases, but ongoing research has revealed the complexities of host-pathogen interactions, including the role of the immune system and microbiomes. Additionally, the identification of viruses and prions expanded the scope of germ theory beyond bacteria. These developments have led to a more nuanced understanding of disease etiology and the factors influencing health.