複選題12. Which of the following status may reflect what we know about how the flu virus moves between species? (A) An animal such as a pig is infected with more than one virus, genetic recombination occurs, the new virus mutates, the virus is passed to a new species such as a bird, and the virus mutates again and can now be transmitted to humans. (B) The flu virus in a pig is mutated and replicated in alternate arrangements so that humans who eat the pig products can be infected. (C) An influenza virus gains new sequences of DNA from another virus, such as a herpesvirus; this enables it to be transmitted to a human host. (D) A farmer is infected by human flu and chicken flu viruses at the same time and the recombinant virus could become highly contagious and virulent for human. (E) There is no avian flu virus can directly infect human.