# 2373
The NEJM (New England Journal of Medicine) has a feature where they display some unique medical image every week. These images vary widely, but they are almost always fascinating . . . assuming it isn't lunch time.
This week the NEJM presents a series of photographs and short video showing the expulsion of air during a single 1/2 second cough.
If you've ever wonder how it is that colds, flu's, and pneumonia's are so easily transmitted, then these images should do the trick. If you were standing next to this guy, you would be breathing in what he is coughing out.
When a healthy volunteer coughs, he expels a turbulent jet of air with density changes that distort a projected schlieren light beam (Panel A). A velocity map early in the cough (Panel B) was obtained from image analysis. Sequential schlieren images during the cough (Panel C and video) were recorded at 3000 frames per second. A maximum airspeed of 8 m per second (18 mph) was observed, averaged during the half-second cough. Several phases of cough airflow are revealed in the figure.
The cough plume may project infectious aerosols into the surrounding air. There is an increasing interest in visualizing such expelled airflows without the use of intrusive methods because of concern regarding the transmission of various airborne pathogens, such as viruses that cause influenza and the severe acute respiratory syndrome (SARS).
Julian W. Tang, F.R.C.Path.
Gary S. Settles, Ph.D.
Pennsylvania State University
University Park, PA 16802
It would have been interesting to see a comparison between an uncovered cough, as shown above, and a cough into one's sleeves or hands.
Imagine being in a crowded bus, subway, or airplane with someone coughing like this.
Notice too, that when the subject coughs, that the spray of particulates begins to drift towards the ground. Larger, heavier droplets are the first to descend. This is one in the ways that inanimate object, or fomites, become contaminated by infected patients.
A person's cough can deposit virus laden droplets on desks, keyboards, telephones . . . practically any surface you can imagine. And those viruses may remain viable, and capable of infecting others, for hours.
The good news here is that the bulk of these droplets appear to drift downward relatively quickly after expulsion, giving credence to idea that maintaining a 6 foot separation between people during a pandemic could help reduce infections.
Of course, the key word here is `reduce'. A far cry from `eliminate'.
The take home message here should be : If you are sick . . . PLEASE STAY HOME.
Now, I've got to go out for awhile. Where did I put those N95 masks?
