11.   After several days the researchers looked for signs that the immune cells had been infected.

12.   But the virus infected only cells that were dividing.

13.   But when cells are infected or otherwise killed, they leak, spilling their insides all over the place.

14.   By blocking its action, the drugs can stop HIV from infecting other cells.

15.   By inhibiting the action of neuraminidase, the drug halts reproduction and stops the virus from infecting other cells in the respiratory tract, they said.

16.   His recent work at Harvard has focused on advancing understanding of how viruses infect human cells and how those cells respond.

17.   If a lentivirus is needed because of its ability to infect nondividing cells, then animal viruses could be used instead of HIV.

18.   If two different type A viruses infect the same cell at once, they can shuffle their gene segments like cards in a deck.

19.   In their study, Andrews and McMichael found viruses that had minor mutations that did not affect their ability to infect cells and proliferate.

20.   In their study, Phillips and McMichael found viruses that had minor mutations that did not affect their ability to infect cells and proliferate.