The new H1N1 swine flu virus has infected at least 1 million Americans, according to the latest estimates from the CDC. Thankfully, most cases are mild. But reports on patients in Mexico confirm that this new virus behaves more like a pandemic string than a typical flu virus. Doctors studying Mexican patients found that 87% of death were in younger people between the ages of 5 and 59. In contrast, just 17% of typical flu death are in this age group
Researchers conclude that if supplies of pandemic vaccine turn out to be limited, then priority should be given to younger generations. A separate analysis notes that this new virus is a relative of an old foe, the 1980 flu that killed millions worldwide. The genes of the 1980 virus have been mixing with other flu strings ever since, triggering periodic pandemics. But there are signs that the pandemics are lessening in severity through the years, possibly because the genes have learned that they can not survive if the virus kills its hosts.

词汇:

Mild: a mild illness or health problem is not serious 温和的，轻微的，不严重的

a mild form of the disease 病势不重

pandemic: (adj.) (疾病)流行性的；传染于(全国、全洲、全世界)的
(n.) 流行病，大流行病

the Aids pandemic in Asia 亚洲流行的艾滋病

foe: 敌人,仇敌

This is the most serious challenge from his political foe.
这是来自他政敌的最严重的挑战。

Host: (寄生动植物的)寄主，宿主