(AP) Put (Type A) H1N1 flu in a room with other strains of influenza, and it does not mix into a new superbug but rather takes over, researchers reported Tuesday.

University of Maryland researchers deliberately co-infected ferrets to examine one of the worst fears about the new H1N1 flu. But fortunately, the flu did not mutate. The researchers carefully swabbed the ferrets' nasal cavities and found no evidence of gene-swapping.

The animals which caught both kinds of flu, however, had worse symptoms. Also, they easily spread the H1N1 flu to their uninfected ferret neighbors but did not spread regular winter flu strains nearly as easily.

In other words, it is no surprise that (Type A) H1N1 flu has become the world's dominant strain of influenza. It is not under evolutionary pressure right now to mix and mutate while it has a clear biological advantage over other kinds of flu, concluded the Maryland team led by virologist Daniel Perez.

The Maryland study, financed by the National Institutes of Health, reinforces worry about how easily H1N1 flu might sweep through a country.

"The results suggest that 2009 H1N1 influenza may out-compete seasonal flu virus strains and may be more communicable as well," said Anthony Fauci, director of NIH's National Institute of Allergy and Infectious Diseases. "These new data, while preliminary, underscore the need for vaccinating against both seasonal influenza and the 2009 H1N1 influenza this fall and winter."

Seasonal human flu vaccine is available around the United States already, and human H1N1 flu vaccine is expected to arrive in mid-October.

The United States has watched closely how (Tyoe A) H1N1 flu rapidly dominated the Southern Hemisphere's winter, as authorities here prepare for a resurgence in the coming months. In Australia alone, eight of every 10 people who tested positive for influenza had the new pandemic strain. While it seems no more deadly than seasonal flu, it claims different victims: Seasonal flu kills mostly people over 65. The new H1N1 flu spreads most easily in children and young adults, and so far has killed mostly people in their 20s, 30s and 40s.

Source: Associated Press