Do you know how many times you coughed today? Or sneezed.. And the days you don’t feel well or have a sore throat. It’s almost like an involuntary thing we just have to do to keep ourselves functioning well. Remarkably, a cough or sneeze is the very first behavior that ever evolved in multi-cellular animals
Yes, sponges can cough and sneeze.

Last night, right after my dinner, I coughed. And coughed again. To a point that it was uncomfortable. And I pondered, why did mom always tell me to cover my cough and sneezes with my hand. Now, if you are an adult reading this – you will readily jump to the conclusion that cough and sneeze can carry germs, and you could give your germs to other people. Alright, I read that too as a child – but can you prove it. And can you prove it right now.
I am thinking a lot about sanitation and hygiene as a global health problem these days. So it would be valuable to actually look (and be able to show readily to a person who does not cover up a cough or a sneeze) – what they are spraying everyone else. So let’s make this abstract idea of one person passing his/her germs to others – visible. Let’s begin.
Experiment/method:

I took a simple clean glass slide. Now, since I wanted to capture particles coming out in my cough on a clean surface, I decided to clean this glass slide further by washing it in my kitchen sink with soap. I really cleaned it well and dryer it with a towel.
An idea of control in science includes when you do the experiment in the null condition. Think of it as the before and after picture. So let’s take the before picture – I mounted my empty glass slide in my foldscope and at 140x magnification, I captured a simple blank image (look carefully – it’s almost blank with very tiny dust).
Now was the big moment, and I just sat with the glass slide in my hand and waited and waited and waited for a natural cough. It was important for me to have a natural cough captured; since I know I could also force a cough. It’s as if my body was very well aware that it was being made a guinea pig and it would not cooperate. I was getting impatient, but soon after I coughed – and I positioned the glass slide right in the path of this explosion.
Why do I call it an explosion. It sounds like one.. It actually looks like one. (Cite). It only takes around a 200 to 500 milli second (so half a second) but it releases probably thousands of tiny little things. Since Foldscope is excellent at deciphering tiny little things – I was quick to put the slide in my foldscope and watch the saga unfold.
What I saw was really amazing.

I saw all kids of debris, microscopic salivary droplets (as small as 10 microns), tiny bacteria and particles and crystals of strange shape and form and finally – my own epithelial cells (the wonderful cells that line up almost all organs of our body). What? I was coughing my own cells out. So off course this is a path for disease transmission – since I am just spraying around all my tiny little bits.
I was incredibly excited to see the intact cells. Although almost a tiny little rocket launch – the cells seemed to have survived the journey. Viability is crucial for some diseases. In a split second; a cell that was happily attached or swimming in saliva lands on another substrate, on a foreign body.

My biggest surprise was these tiny little needle like crystals. I don’t know what they are; but they are beautiful. Please comment below if you have a theory about the same. Lots of other little bits and pieces, dead shreds.

Finally, as the saliva droplets start to evaporate; I see crystal formation. They are quiet incredible too.

Now, I sincerely hope you will repeat this experiment and share what else are you coughing out. And as always, remember what your mother used to tell you; always cover up your cough or sneeze. You don’t want to be the one transferring your germs to other..
Cheers

Manu
Other fun cough and sneeze puzzles:
1) Fluid dynamics of coughing and sneezing:

http://lbourouiba.mit.edu/publications