The virus which is behind the incidence of common cold may actually protect against swine flu, a new study has revealed.
In the study, researchers found that that the percentage of throat swabs from French respiratory illnesses that tested positive for swine flu, fell in September, while at the same time rhinovirus, which causes colds, rose.
Jean-Sebastien Casalegno of the French national flu lab at the University of Lyon, said that in late October, rhinovirus fell - at the same time as flu rose.
He believes rhinovirus may have blocked the spread of swine flu via a process called viral interference.
"We think that when you get one infection, it turns on your antiviral defenses, and excludes the other viruses," New Scientist quoted Ab Osterhaus at the University of Rotterdam in the Netherlands, as saying.
However, process of interference is unclear, as there have been cases where there is no interference, and people catch two viruses at the same time.
In another study, Mia Brytting of the Swedish Institute for Infectious Disease Control in Solna, reported a rise in rhinovirus coupled with a decrease in swine flu.