The study provides the first evidence that vomiting could aerosolize the norovirus.
North Carolina State University researchers state that their study, published in PLOS ONE, will have implications for better understanding how the human form of the virus is transmitted and for improving infection control measures.
"Epidemiological studies have suggested that norovirus can be 'aerosolized' through vomiting, meaning that small particles containing norovirus can become airborne when someone throws up," says Grace Tung-Thompson
Norovirus, the most common cause of acute gastroenteritis in the US, has typically been understood to be transmitted through contact with infected people, touching contaminated surfaces or consuming contaminated food or water.
"According to outbreak reports, it appears that people can become infected with [norovirus] if they are directly or indirectly exposed to vomiting events," Tung-Thompson adds. "If aerosolized particles land on a countertop, you could also touch the counter with your hand, then touch your hand to your mouth, leading to infection."
Researchers did not know, however, precisely how the virus becomes aerosolized. To investigate, researchers from Prof. Lee-Ann Jaykus' laboratory developed a novel machine to explore the process of vomiting.
Their vomiting machine consists of a scaled-down replica of the human mouth, esophagus and stomach. Users of the machine can control the volume, viscosity and pressure of the simulated vomiting, allowing them to emulate a range of natural vomiting behaviors and stages of digestion.
The video below demonstrates how the vomiting machine works:
A bacteriophage called MS2 that is harmless to humans was used as a stand-in for norovirus - as is often the case in research. By contaminating the artificial vomit with this virus, the researchers aimed to find out if the virus became aerosolized after vomiting and how much of it became airborne.
Vomiting aerosolizes 'enough of the virus to cause infection'
The researchers found that 0.02% of the total virus in the vomit became aerosolized - an amount that would be enough to cause infection.
- Norovirus is the most common cause of disease outbreaks from contaminated food in the US
- The virus causes 19-21 million illnesses in the US each year
- Norovirus can still be detected in dried vomit up to 6 weeks after someone has thrown up.
"In terms of overall percentage, not a lot of the virus is aerosolized," explains co-author Francis de los Reyes III, a professor of civil, construction and environmental engineering. "But in absolute terms, it is a lot compared to the amount of virus needed to cause infection."
"This machine may seem odd, but it's helping us understand a disease that affects millions of people," reports Prof. Jaykus. "This is work that can help us prevent or contain the spread of norovirus - and there's nothing odd about that."
Prof. de los Reyes told Medical News Today that "the focus of future research is on transmission pathway details." These include the potential impact of airflow in a room and how far airborne particles can travel.
For now, though, the vomiting machine has served its purpose. Prof. de los Reyes told MNT that although it could be used to look at the bioaerosolization of bacteria during vomiting, there are no plans to do this at present.
Previously, MNT reported on a study that raises the question of whether humans can catch norovirus from dogs. The authors found that some dogs can have an immune response to human norovirus, suggesting that they have been infected by the virus.