Study: H1N1 flu more virulent than thought

MADISON, Wis., July 14 (UPI) -- A team of U.S. virologists says the H1N1 flu virus pathogen is more virulent than previously thought.

Study leader Yoshihiro Kawaoka of the University of Wisconsin-Madison says that in contrast with run-of-the-mill seasonal flu viruses, the H1N1virus, commonly referred to as swine flu, exhibits an ability to infect cells deep in the lungs, where it can cause pneumonia and, in severe cases, death. Seasonal viruses typically infect only cells in the upper respiratory system, Kawaoka says.

"There is a misunderstanding about this virus," Kawaoka said in a statement. "People think this pathogen may be similar to seasonal influenza. This study shows that is not the case. There is clear evidence the virus is different than seasonal influenza."

The ability to infect the lungs, a quality frighteningly similar to those of other pandemic viruses such as the Spanish flu in 1918, which killed tens of millions.

The study, published in the journal Nature, also shows that people born before 1918 harbor antibodies that protect against the new H1N1 virus.

Several hundred swine flu deaths and about 100,000 cases have been have been confirmed worldwide since the outbreak started in Mexico in April, the World Health Organization says. The virus is expected to return in force to the northern hemisphere during the fall and winter flu season.