Bird flu study shows human cell barrier

MADISON, Wis., March 22 (UPI) -- A University of Wisconsin-led international study reveals an anatomical cell difference that makes it difficult for a virus to jump from human to human.

Although more than 100 people have died from the H5N1 avian influenza virus, the fact the virus doesn't spread easily from its pioneering human hosts to other humans has been a biomedical puzzle.

The UW-Madison finding, reported in the journal Nature, is important because it demonstrates a requisite characteristic for the virus to equip itself to easily infect humans.

The report issued by a research group led by virologist Yoshihiro Kawaoka describes experiments that show only cells deep within the respiratory system have the surface molecule or receptor that permits the avian flu virus to enter a cell.

"Our findings provide a rational explanation for why H5N1 viruses rarely infect and spread from human to human, although they can replicate efficiently in the lungs," the authors of the study write in the Nature report.

The study was conducted in collaboration with Kyoko Shinya and Shinya Yamada of the University of Tokyo; Masahito Ebina and Masao Ono of Tohoku University; and Noriyuki Kasai of the Institute for Animal Experimentation in Japan.