If medical researchers fail to cook up a cure for the common
cold in our lifetime, it won't be for lack of trying. The cold
may be a relatively trivial annoyance, but it's not even close
to a trivial problem. Despite its name, for instance, the common
cold is caused by not one common virus but five different viral
families, encompassing a couple of hundred unique viral strains
among them. These strains are sufficiently different from one
another that even after catching one, we can later be infected
and rendered miserable by all the others. This explains why
toddlers seem to be in a continuous state of sniffles--being
tabulae rasae for every strain that comes along--while adults
become ever more immune with each ensuing cold and often go
years before encountering a strain they've never had. The
regrettable implication is that researchers will have to come up
with a cure for every family and strain, or at least most of
them. Otherwise any treatment is likely to fail too frequently
to fire the public's enthusia