That's right, what you're looking at is some nasty bastard coughing, and the resulting air turbulence. Sick!
Schlieren photography involves shining collimated light past a knife edge onto a target, and variations in the refractive index of moving air create "shadows" of a sort in the image captured on film, and it's most often used to solve aeronautical air-flow problems, or weapons in action.
Okay, I don't understand what that means. But scientists plan to use the data gathered from these photos to study the spread of diseases like SARS, AIDS, the herp, the clap, the snap, the shocker, the Spocker, the body rocker, gingivitis, crabs, and hangnails. Just kidding, not SARS.