21.   The virus has a couple of weaknesses that may help check its spread, Kuo says.

22.   The virus has a long incubation period, often lingering in a human body for more than a decade before making itself known in a serious illness.

23.   The virus has no impact on standard DVD players.

24.   The virus has no vaccine or drug treatment regimens.

25.   The virus also had the technical services departments at Boston-area firms scrambling.

26.   The virus has an incubation period of about a decade before progressing to AIDS.

27.   The virus has an incubation period of three to six weeks.

28.   There was no test for the AIDS virus or effective treatment, the virus had yet to be isolated and authorities had not proved it was sexually transmitted.

29.   Though no one can be sure how cidofovir would work in people with smallpox, its effectiveness against related pox viruses in animals has impressed researchers.

30.   Up to now, viruses have had great difficulty getting into your computer this way.