The puzzle of the evolutionary dynamics of influenza
(University "Federico II", Naples)
Influenza exhibits two apparently contradictory features:
on the one hand, any given individual can get infected
with the disease over and over again, since the
virus mutates fast enough to escape acquired immunity;
on the other hand, on any given epidemic season, the
viral strain is sufficiently well-defined, so that an effective
vaccine can be identified. It represents a
problem in evolutionary dynamics in which the molecular
level and the epidemiological level are tightly bound.
Several mechanisms have been proposed to explain
this behavior, but a satisfactory answer is still
lacking. I shall review the recent debate on the subject and
point out the most promising directions of research.