Protein signatures
It relies on the fact that bacteria and viruses can trigger different protein pathways once they infect the body.
A novel one, called TRAIL, was particularly high in viral infections and depleted during bacterial ones. They combined this with two other proteins - one is already used in routine practice.
Prof Jonathan Ball, a virus expert at Nottingham University, said: "The work addresses a really serious problem. Being able to identify a possible infection early on and then to be able to differentiate between a possible viral or bacterial cause, is important.
"This will allow informed clinical intervention and minimize the need for inappropriate use of antibiotics, for example with someone infected by a virus.
"It will be important to see how it performs in the long-term."