科学美国人60秒:Vomit Machine Models Cruise-Ship Virus Spread

There's no question that catching norovirus, famous for turning some luxury cruises into horrors at sea, is a terrible ordeal. "I oftentimes say, you generally don't die but you feel like you want to die." Lee-Ann Jaykus, a food microbiologist at North Carolina State University. "Many people experience norovirus as what's called 'projectile vomiting,' which is literally, across the room."

Epidemiological studies have suggested that such spirited spewing can aerosolize the virus, putting others at risk. But Jaykus says that mode of transmission has never been verified. "You know, in an ideal world you'd have somebody who had norovirus vomit, and then you probably would collect the aerosols that came out of that vomiting event." Sadly, or maybe thankfully, our world is not ideal. So instead, "we decided to build a simulated vomiting device." Yep, you heard right: "a simulated vomiting device." 

The device mimics the upper GI tract: an artificial stomach with a pressure pump, and a ball valve 'sphincter muscle,' leading up to the esophagus and throat. Vomit spews from a human-looking mask into a plexiglass box, where air can be sampled for aerosols. As for the vomit? "People don't like to give researchers their vomit to analyze." So they mixed up one saliva-like vomit solution, and another, custardy one using vanilla pudding. Then they doped both with a harmless virus, similar to norovirus in shape and structure.

The researchers shot both vomits through the device, and took air samples. And indeed, in every test, they detected airborne viruses, albeit in small numbers: ?usually ?less than one hundredth of one percent of the bugs present in the original samples. But that's still significant, Jaykus says, because previous studies suggest ?that? ?millions of virus?es can ?be released in a single bout of vomiting. Which means "You come up with numbers like 50 to well over 10,000 virus particles getting into the air." That's a lot, she says, considering that ?just 20 particles could be enough to make some people sick. The study appears in the journal PLOS ONE. [Grace Tung-Thompson et al, Aerosolization of a Human Norovirus Surrogate, Bacteriophage MS2, during Simulated Vomiting]

As for avoiding the aerosols—how about the ol' holding-your-breath trick when you’re in the vicinity of vomit? "It's probably not very effective." Better, she says, assuming the victim's being cared for, is to get as far away as you can. As if you needed to be told.

—Christopher Intagliata

[The above text is a transcript of this podcast.]