3 COVID-19 ‘ ’ . 1970 · , . (CDC) 51 5 , . 30 DC, 460 . ( ·) (WHO) 1980 '' . , . 1950 . , . 19 . , , , . . . 6~13, 21 , , , , , . 2~4 , , . WHO 3~6% . . , 85% . , . . 19 , . (, Epidemic) , … [+118 chars]