The word "virus" was generally referred to as a poison associated with disease and death at the time of:

Explanation

The correct answer is Louis Pasteur and Robert Koch. During the late 19th century, the term 'virus' was primarily used to describe infectious agents and was often associated with the concept of poison, particularly in relation to diseases. Pasteur's work on vaccines and Koch's postulates laid the foundation for understanding pathogenic organisms, including viruses. The other options are incorrect because while they include notable scientists, they do not accurately reflect the historical context of the term 'virus' as a poison associated with disease. Charles Chamberland, for example, focused on filtration methods rather than the terminology, and Ivanowsky's work, although significant in virology, did not establish the term in the same context.