Study: 1918 flu survivors seem immune to swine flu

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.