1. Why do people who are immunized sometimes still get the flu? 2. What do the letter A,H, and N stand for in the name A(H5N1)? 3. Why are epidemiologists particularly concerned about bird influenza viruses?
Extracted text: Flu viruses infect birds, pigs, horses, and humans. These viruses normally mutate, producing slightly different strains every year-a process called antigenic drift. About once a decade, however, different strains of influenzaviruses infect a single cell, and within it they exchange major pieces of RNA, producing a new, quite different strain of virus-a process called antigenic shift. The virus attacking Jessica was such a newly emerged influenzavirus, a strain that contained RNA from influenzaviruses of humans, birds, and swine in a novel combination. The virus, commonly called swine flu virus, is officially A(H5N1).
Extracted text: School is supposed to be a time of exploration, learning, and fun, but Jessica was too sick to enjoy it right now. Her 104°F fever had lasted two very unpleasant days, but at last it had gone. For another two days she ached all over and was dizzy; her head felt as if it could explode at any moment; and the nausea, frequent vomiting, and extreme tiredness were unrelenting. For over a week, her tired red eyes stared listlessly as she struggled to cope with a constantly running nose, severe sore throat, and a dry hacking cough. Would this onslaught never end? A newly emerging strain of influenza type A had a victim in its grasp.