Bacteria, despite causing hundreds of different types of infection, essentially reproduce and spread in the same way.

A single "broad spectrum" antibiotic may be able to tackle dozens of different types.

However, viruses are split into seven different main types - all of which use widely differing methods to replicate.

Common threads

Creating a drug which can tackle each class is enough of a challenge - but making one which can handle more than one class is seen as a much greater problem.

However, researchers at the Howard Hughes Medical Institute in the US believe they have found a common process that links three of the virus types.

Studies of the replication process of the virus by the Howard Hughes Institute researchers revealed that, while each type used different genetic tricks to copy itself, one vital stage of the process involved creating a "bud" to contain genetic material from the virus.

The researchers believe that a future drug which disrupted the formation of the "bud" could hold the key to interrupting the progress of dozens of viruses.

Long wait

Researcher Paul Ahlquist said: "Recognition of these links means that principles learned from a variety of virus systems could be used to illuminate many others, allowing integration and generalisation of knowledge across a wide range of important viruses."

He did concede that much remained to be done before new treatments could be developed.

Dr Alan Cann, a virologist from the University of Leicester, agreed that many hurdles had to be overcome before new "broad spectrum" antiviral drugs could be developed.

He said: "The biggest problem for antiviral drugs is that viruses are so tied into the biochemistry of human cells.

"It's hard to find a way to harm them without being toxic to the cell itself.

"The eventual hope might be for a general-purpose antiviral drug which could perhaps be given by GPs for a wide range of viral infections.

"This is likely to take a long time to produce."

The research was published in the journal Molecular Cell.