In contrast with run-of-the-mill seasonal flu viruses, the H1N1virus 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.
"There is a misunderstanding about this virus," says Kawaoka, a professor of pathobiological sciences at the UW-Madison School of Veterinary Medicine and a leading authority on influenza. "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, notes Kawaoka, is a quality frighteningly similar to those of other pandemic viruses, notably the 1918 virus, which killed tens of millions of people at the tail end of World War I. There are likely other similarities to the 1918 virus, says Kawaoka, as the study also showed that people born before 1918 harbor antibodies that protect against the new H1N1 virus.
And it is possible, he adds, that the virus could become even more pathogenic as the current pandemic runs its course and the virus evolves to acquire new features.