When could an epidemic stop and die out?

What does herd immunity mean?

Which of the following would provide evidence that a parasite and its host have co-evolved?

Which of the following is an accurate statement of relationships?

Which of the following cell types can kill cells that present antigens via MHC on their cell surface?

When did HIV-1 group M likely first emerge in humans in central Africa?

Which of the following are components of the virulence-transmission tradeoff hypothesis? Select all that apply.

Which of the following is an appropriate explanation for the large diversity of lymphocyte receptors?

For which of the following receptor proteins do the corresponding genes undergo somatic recombination?

In terms of genome organization, what type of viruses are retroviruses?