Researchers discover highly infectious vehicle for virus transmission among humans

August 8, 2018, NIH/National Heart, Lung and Blood Institute
Illustration of membrane-bound vesicles containing clusters of viruses, including rotavirus and norovirus, within the gut. Rotaviruses are shown in the large vesicles, while noroviruses are shown in the smaller vesicles. Credit: NIH

Researchers have found that a group of viruses that cause severe stomach illness—including the one famous for widespread outbreaks on cruise ships— get transmitted to humans through membrane-cloaked "virus clusters" that exacerbate the spread and severity of disease. Previously, it was believed that these viruses only spread through individual virus particles. The discovery of these clusters, the scientists say, marks a turning point in the understanding of how these viruses spread and why they are so infectious. This preliminary work could lead to the development of more effective antiviral agents than existing treatments that mainly target individual particles.

The researchers studied norovirus and rotavirus—hard-to-treat viruses that are the most common cause of stomach illness, or gastroenteritis, and that afflicts millions of people each year. The viruses cause symptoms ranging from diarrhea to abdominal pain and can sometimes result in death, particularly among young children and the elderly. Their highly contagious nature has led to serious outbreaks in crowded spaces throughout many communities; most notably in cruise ships, daycare centers, classrooms, and nursing homes. Fortunately, vaccines against rotavirus are now available and are routinely given to babies in the United States.

"This is a really exciting finding in the field of virology because it reveals a mode of spread that has not been observed among humans and animals," said study leader Nihal Altan-Bonnet, Ph.D., senior investigator and head of the Laboratory of Host-Pathogen Dynamics at the National Heart, Lung, and Blood Institute (NHLBI). "We hope that it will provide new clues to fighting a wide range of diseases involving many types of viruses, including those that cause gastrointestinal illnesses, heart inflammation, certain respiratory illnesses, and even the common cold."

The study was supported in part by the Intramural Research programs of the NHLBI and the National Institute of Allergy and Infectious Diseases (NIAID), both part of the National Institutes of Health. It is featured as the cover story of Cell Host & Microbe and is scheduled for online publication on August 8.

Illustration showing fecal-oral transmission of membrane-bound vesicles containing clusters of rotavirus and norovirus. Vesicles produced in the gut of infected individual are shed into stool before being spread to other individuals, where they can cause severe gastrointestinal illnesses. Credit: NIH

Until a few years ago, most scientists believed that viruses, particularly those responsible for stomach illnesses, could only behave as independent infectious agents. However, in 2015 Altan-Bonnet and her colleagues showed that polioviruses could transmit themselves in packets, or membrane-bound vesicles containing multiple virus particles. The scientists compared this new model of viral transmission to a Trojan horse: A group of membrane-bound viruses arrives at a host cell and deposits viruses in the cell while dodging detection by the immune system. The scientists did not know whether this system applied to animals and humans, or how effective these packets were in infecting host cells.

To find out, they focused on rotaviruses and noroviruses, which mainly get spread by accidentally ingesting tiny particles of an infected person's stool—through, for example, contaminated food or liquids. The researchers obtained fecal samples of humans and animals (pigs and mice) and found that the viruses are shed in the stool as virus clusters inside membrane-bound packets. In addition, they found that these virus-containing vesicles were significantly more infectious than the free, unbound viruses within the samples.

The researchers determined that the high level of infectiousness was likely due to the vesicles delivering many viruses at once to the target tissues; protecting their viral cargo from being destroyed by prolonged exposure to enzymes; and possibly by making their viral cargo invisible to the antibodies that are in the stool or gut of the host. More studies are needed, but the extreme potency of the virus packets, they said, has a clear consequence: it not only enhances the virus' ability to spread more aggressively; it also increases the severity of the disease it causes.

"Our findings indicate that vesicle-cloaked viruses are highly virulent units of fecal-oral transmission and highlight a need for antivirals targeting vesicles and virus clustering," Altan-Bonnet noted. Handwashing with soap and water helps prevent the spread of .

Explore further: Scientists create 3-D structure of 1918 influenza virus-like particles

Related Stories

Scientists create 3-D structure of 1918 influenza virus-like particles

July 11, 2018
Virus-like particles (VLPs) are protein-based structures that mimic viruses and bind to antibodies. Because VLPs are not infectious, they show considerable promise as vaccine platforms for many viral diseases, including influenza. ...

Ebola virus exploits host enzyme for efficient entry to target cells

February 7, 2018
Researchers have identified a key process that enables the deadly Ebola virus to infect host cells, providing a novel target for developing antiviral drugs. The Ebola virus incorporates a cellular enzyme into its virus particles, ...

Recommended for you

PET scans to optimize tuberculosis meningitis treatments and personalize care, study finds

December 6, 2018
Although relatively rare in the United States, and accounting for fewer than 5 percent of tuberculosis cases worldwide, TB of the brain—or tuberculosis meningitis (TBM)—is often deadly, always hard to treat, and a particular ...

Silicosis is on the rise, but is there a therapeutic target?

December 6, 2018
Researchers from the CNRS, the University of Orléans, and the company Artimmune, in collaboration with Turkish clinicians from Atatürk University, have identified a key mechanism of lung inflammation induced by silica exposure, ...

Infectivity of different HIV-1 strains may depend on which cell receptors they target

December 6, 2018
Distinct HIV-1 strains may differ in the nature of the CCR5 molecules to which they bind, affecting which cells they can infect and their ability to enter cells, according to a study published December 6 in the open-access ...

Protecting cell powerhouse paves way to better treatment of acute kidney injury

December 6, 2018
For the first time, scientists have described the body's natural mechanism for temporarily protecting the powerhouses of kidney cells when injury or disease means they aren't getting enough blood or oxygen.

New study uncovers why Rift Valley fever is catastrophic to developing fetuses

December 5, 2018
Like Zika, infection with Rift Valley fever virus can go unnoticed during pregnancy, all the while doing irreparable—often lethal—harm to the fetus. The results of a new study, led by researchers at the University of ...

Study highlights potential role of bioaerosol sampling to address airborne biological threats

December 5, 2018
As a leading global city with a high population density, Singapore is vulnerable to the introduction of biological threats. Initiating an early emergency response to such threats calls for the rapid identification of the ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.