New U.S. research suggests there is no need to worry that the swine flu virus could mutate to become more deadly or to spread more easily than it already does. H1N1 is already well adapted to humans and is crowding out other strains, the research has found.
There had been worries that H1N1 would "reassort" by swapping genes with seasonal flu strains to become a more dangerous superbug. There have also been worries the virus was not yet completely adapted to humans and that additional changes could lead to a more dangerous strain.
But virologists reporting in the online journal PLOS Currents say H1N1 appears to outperform other flu viruses. Instead of mixing with other flu viruses, swine flu seems to crowd the other strains out.
Virologist Daniel Perez and his team of researchers at the University of Maryland came to their conclusions by studying how the virus operates in ferrets. (Ferrets were chosen because they have been shown to be an accurate model for human flu infection.)
They inoculated the weasels with H1N1 plus one strain of seasonal flu: either another H1N1 strain or an H3N2 virus in a laboratory setting. Only the swine flu virus was transmitted from co-infected ferrets to uninfected ferrets; there was no evidence that either seasonal flu viruses were transmitted.
That lends further evidence that H1N1 will probably predominate in the coming flu season, the researchers conclude.
The researchers also studied tissue from the ferrets' nasal cavities and found no evidence that the H1N1 virus had combined with the two seasonal flu viruses to form new, so-called reassortant viruses.
The findings suggest there may not be biological pressure for the new virus to re-combine with other circulating viruses, the researchers say.
"The H1N1 pandemic virus has a clear biological advantage over the two main seasonal flu strains and all the makings of a virus fully adapted to humans," Perez said in a statement announcing the findings.
Dr. Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases (NIAID) says the research provides doctors with more clues about what to expect this flu season.
"This elegant study, conducted in a useful animal model of human influenza, provides important information about how the 2009 H1N1 influenza virus interacts with other flu virus strains," Fauci said in the statement.
The researchers also noted that some of the co-infected ferrets developed intestinal illness in addition to respiratory systems.
As well, those ferrets co-infected with the H3N2 strain seemed to develop more severe illness.
The researchers say more research is needed to see whether being infected by two strains at once might explain some of the deaths linked to swine flu.
