11.   The Hepatitis B viral infection is one of the most serious of the three viral strains of hepatitis.

12.   The laboratory work, however, seems to run counter to what occurs when a person is simultaneously infected by both viral strains.

13.   The viral strain isolated in the boy is still deadly to chickens, though.

14.   They found the viral strain had two major proteins against which humans have little or no immunity.

15.   Tracking influenza outbreaks and changes in viral strains is a bit like tracking hurricanes.

16.   Two-thirds were given a spray containing a cocktail of three viral strains, the other third a placebo.

17.   We talked about how HIV mutates rapidly, and the same viral strain can evolve differently in different individuals with different immune systems and genetic makeups.

18.   Ebola Sudan, one of three viral strains that can infect humans, has been identified as responsible for the outbreak in the Gulu area.

19.   This particular type of chimp in Tanzania could not be the source for human AIDS, because the viral strain the researchers found is too genetically different.

20.   A new and potentially fatal viral strain carried by Australian fruit bats and linked to rabies has become a national problem, health authorities said Monday.