Common cold: Shown here is the structure of the protein shell, or capsid, of the human rhinovirus. Credit: J. Y. Sgro, UW-Madison

We may be one step closer to defeating that small but mighty bearer of human misery: the common cold.

Scientists have now sequenced all of the 99 known strains of cold virus. The research, published today in the journal Science, sheds light on the bug's ubiquity--different viruses can swap DNA sequences, generating new strains that can evade the immune system.

According to a statement from the University of Wisconsin:

The newly sequenced viruses also show ... why it is unlikely we will ever have an effective, all-purpose cold vaccine: The existing reservoir of viruses worldwide is huge and, according to the new study, they have a tendency to swap genetic sequences when cells are infected by more than one virus, a phenomenon that can lead to new virus strains and clinical manifestations.

"Having sequenced the complete genomes of these things, we now know you can be infected by more than one virus at a time and that they can recombine (their genes)," [lead author of the new study Ann] Palmenberg [of UW-Madison's Institute for Molecular Virology] explains. "That's why we'll never have a vaccine for the common cold. Nature is very efficient at putting different kinds of paint on the viruses."