Researchers at Leeds and York have cracked the encrypted code used by a major group of viruses including the common cold and polio to spread the infection within the body.

By jamming the code hidden in the viral RNA sequence using designer molecules, it is possible to make it unreadable and halt the virus in its track.

The code basically initiates the virus assembly and functioning.

Viruses which are a hundred times smaller than human cells multiply by hijacking the cell's replication mechanism once inside. The cell starts to make many copies of the virus which then burst out of the cell, destroying it and proceeding to infect other cells.

By interfering with the RNA code, the very process of virus assembly is halted.

Professor Peter Stockley, Professor of Biological Chemistry in the University of Leeds' Faculty of Biological Sciences, who led the study, said: "Now, for this whole class of viruses, we have found the 'Enigma machine'--the coding system that was hiding these signals from us. We have shown that not only can we read these messages but we can jam them and stop the virus' deployment."

Single-stranded RNA viruses are the simplest type of virus and believed to be one of the earliest to evolve. However, like the rhinovirus that causes common cold, they account for more infections than all other infectious pathogens put together.

Emergent infections such as chikungunya and tick-borne encephalitis are from the same ancient family.

Hepatitis C and HIV

Other single-stranded RNA viruses include the hepatitis C virus, HIV and the winter vomiting bug norovirus.

In 2012, researchers at the University of Leeds first observed a single-molecule level of how the core of a single-stranded RNA virus packs itself into its outer shell in milliseconds.

University of York mathematicians working with the Leeds group then devised mathematical algorithms to crack the code governing the process and built computer-based models of the coding system.

In the latest study, the two used single-molecule fluorescence spectroscopy to watch the codes being used by the satellite tobacco necrosis virus, a single stranded RNA plant virus.

The study paper was published in the Proceedings of the National Academy of Sciences (PNAS).

Dr Roman Tuma, Reader in Biophysics at the University of Leeds, said: "We have understood for decades that the RNA carries the genetic messages that create viral proteins, but we didn't know that, hidden within the stream of letters we use to denote the genetic information, is a second code governing virus assembly. It is like finding a secret message within an ordinary news report and then being able to crack the whole coding system behind it."

Professor Reidun Twarock, of the University of York's Department of Mathematics, said: "We found multiple dispersed patterns working together in an incredibly intricate mechanism and we were eventually able to unpick those messages. We have now proved that those computer models work in real viral messages."

Most viruses get their genetic material from RNA, and most of the coded genetic information is for just a handful of proteins, as compared to about 20,000 in humans.

Most of the viral genome lies hidden under layers of fat or lipid. What are exposed are a few surface proteins, and about 10% of those proteins are used by the virus to enter and infect a cell.

The immune system works by recognising the proteins on the surface of the virus. But many viruses mutate and cause these proteins to keep changing, making it difficult to target the virus using vaccines or drugs.

The single-molecule detection capabilities and computational models used in the latest study are expected to help in novel drug discovery.