To study how viruses spread through the air when we throw up, researchers have built a vomiting machine, complete with a clay face and a mouth that spews fake barf. According to their findings, published in PLOS ONE this week, upchucking makes virus particles airborne.
Around the world, human noroviruses are the leading cause of acute gastroenteritis, or the stomach flu. These infections can occur when we consume contaminated food or water, though they spread more often through close contact between people. Exactly how it’s transmitted hasn’t really been tested. “Epidemiological studies have suggested that norovirus can be ‘aerosolized’ through vomiting, meaning that small particles containing norovirus can become airborne when someone throws up,” North Carolina State University’s Grace Tung-Thompson says in a statement. These viruses make us throw up, but does throwing up help to spread them?
To see if that’s the case, she and colleagues developed a vomiting device that allowed them to control the volume, viscosity (or thickness), and pressure of simulated “vomitus.” It consists of a simple mouth, esophagus, and stomach made of tubing, valves, and a pressure chamber attached to a hand pump; a clay face weighs down the end of the tube to provide the correct vomiting angle. The whole thing is contained within a see-through and sealed Plexiglas box with a sampling port. And rather than using real barf filled with noroviruses, the team used fake vomit – artificial saliva or vanilla instant pudding, depending on the stage of digestion – and then contaminated it with a common stand-in virus. Called the MS2 bacteriophage, this pathogen infects E. coli and is harmless to us.
Photo of a Simulated Vomiting Episode. Projectile vomiting of colored simulated vomitus matrix. G. Tung-Thompson et al./PLOS ONE.
Vomiting, they confirmed, aerosolizes the virus, though the amount that’s aerosolized was relatively low. “At most, only 0.02% of the total virus in the vomit was aerosolized,” NC State’s Lee-Ann Jaykus explains in another statement. “But that can still amount to thousands of virus particles – more than enough to infect other people.” After all, vomit from infected people contains millions of particles, and it only takes about 20 to sicken a susceptible person.
“When one person vomits, the aerosolized virus particles can get into another person’s mouth and, if swallowed, can lead to infection,” Jaykus adds. “But those airborne particles could also land on nearby surfaces like tables and door handles, causing environmental contamination. And norovirus can hang around for weeks, so anyone that touches that table and then puts their hand to their mouth could be at risk for infection.”
Next, the team wants to see how long virus particles can remain airborne and how far they can travel in the air.