21.   Microscopic studies showed the virus attacked cancer cells but caused no infection in normal, healthy brain cells, he said.

22.   The AIDS virus attacks humans by destroying their immune systems, making them susceptible to other illnesses.

23.   The AIDS virus attacks the very parts of the immune system that are ordinarily called into action by effective vaccines.

24.   The Ebola virus rarely attacks humans, but is one of the deadliest known to scientists.

25.   The highly infectious virus attacks the nervous system, causing paralysis in a matter of hours.

26.   The nasal vaccine stimulates the immune system through the same nose tissue where the flu virus attacks.

27.   The nasal vaccine works by stimulating the immune system through the same nose tissue where the flu virus attacks.

28.   The virus attacks the central nervous system and can weaken the immune system and muscles.

29.   The virus attacks the respiratory system as well as other organs, and several of those who died had developed pneumonia.

30.   The virus attacks through the nose.