Study: 1918 flu survivors seem immune to H1N1

WASHINGTON – The way swine flu multiplies in the respiratory system is more severe than ordinary winter flu, a new study in animals finds.

Tests in monkeys, mice and ferrets show that the swine flu thrives in greater numbers all over the respiratory system, including the lungs, and causes lesions, instead of staying in the nose and throat like seasonal flu.

In addition, blood tests show that many people who were born before the 1918 flu pandemic seem to have immunity to the current swine flu, but not to the seasonal flu that hits every year.

The research by a top University of Wisconsin flu researcher was released Monday and will be published in the journal Nature.

“I’m very concerned because clearly the (swine flu) virus is different from seasonal influenza,” said study lead author Yoshihiro Kawaoka. “It’s a lot more severe.”
But it is still not as severe as the 1918 influenza, he said.

With only a few months since swine flu was first identified, doctors are still trying to get a handle on this flu strain and how it is different from the yearly seasonal flu.

On Monday, officials at the Centers for Disease Control and Prevention said swine flu is acting differently than seasonal flu and they aren’t comparing its virulence to the run-of-the-mill influenza, which kills about 36,000 Americans per year.

Unlike seasonal flu, the new swine flu is continuing into the summer, and has caused severe illness mostly in younger people instead of the elderly, the Centers for Disease Control and Prevention said.

But Kawaoka did not find that. He checked blood samples from a wide number of age groups. With two exceptions, he found only people who were born before the 1918 pandemic to have immunity.