Steven:

The only underlying condition that one needs in order to contract
sinusitis is to contract a cilia-killing respiratory virus.
The pathogens in the normal flora of the nose can then latch on and
establish permanent biofilms which we are still ignoreing.

You have been seduced by the success of the vaccinations that we
recieve as children into an idea that people do NOT get infectious
diseases unless there is some "underlying condition". Diptheria and
pretussus are quite sufficent in and of themselves to cause
strangleing disease, TB, cholera and e c H157, typhoid, only have to
be there they do not require an "underlying condition".
 There are other bacteria which are visably present but resist
growing in a monoculture and so remain to be characterized. The work
has not done. The work is not done until it has been done!  I see a
film of what looks like and reacts like e-coli at the interface in my
samples and in the published micrographs that I have seen of other
sinusitis tissue samples.

My long term hope is for a anti-sinusitis vaccination but that will
not be developed as long as viruses and bacteria are not recognised as
the cause of the disease.