Preview the following introduction. Provide in your own words a topic sentence and conclusion statement based on what you read in “1918: On the Trail of Influenza”. While the world was caught up in fighting enemies they could see, an enemy far too small for them to keep an eye on was spiraling out of control. Most pathogens, like the influenza virus, are so small they must be viewed with a microscope. How could something so small have such a big effect?