Scientists have discovered how the virus that causes most cases of diarrhoea invades cells.
Children in the developing world are particularly vulnerable
The Boston Children's Medical School team say the finding could help develop an vaccine to combat the rotavirus.
The virus, the most common cause of severe, dehydrating diarrhoea, kills around 440,000 children a year, mainly in developing countries.
Writing in Nature, the researchers say understanding more about the virus will help them fight it successfully.
The researchers say their work shows how vaccine development can be made "smarter" by looking at the physical make-up of viruses and finding the minimum parts needed to prime the immune system, without having to use a whole virus to make a vaccine.
Almost all children are infected with the rotavirus as toddlers. It can cause gastroenteritis that is sometimes severe enough to require hospital care.
Breaking into cells
Scientists have been working to develop a vaccine which will be effective against the virus for some time.
Two vaccine have been licensed. One was used in the US, but was withdrawn after it was linked to a condition which causes bowel obstruction. The second has only been licensed for use in China.
The researchers in this study examined the geometric structure and behaviour of one of the rotavirus's surface proteins, called VP4, which plays a key role in binding on to the surface of a target cell, and breaking through its membrane.
The key finding for vaccine development is that the "head" and "body" portions of the VP4 protein contain many of the targets that the immune system recognises when it attacks the virus and protects against infection, they say.
"The work is a clear example of the way in which structural studies can contribute to new good ideas about strategies for vaccines," said Dr Stephen Harrison, head of the Children's Medical Hospital Laboratory of Molecular Medicine.