Everywhere in hospitals or even out of hospitals, can be
breeding grounds and spreading grounds for viruses and bacteria and
what-not. 
In the ICU, a lot of patients are on ventilators, they are weakened
and in an immuno-compromised state because of their serious
illnesses, which put them there in the first place.
Being on the ventilator puts one at risk for Ventilator-Acquired
Pneumonia because there are many points of possible infection for
the patients.
All said, there are germs and superbugs that originate from
hospitals but do not go out into the community because the very ill
are more susceptible.
And THAT is why we prohibit children from under 12 to enter the
wards and visit the patients!
And yet, when I walk up to parents and try to explain that the
hospital is not a good and safe area to bring their babies and
toddlers in, they complain to my ward sister that I was 'rude',
that I 'tried to prevent them from visiting the sick relatives',
etc etc etc. And mind you, I have colleagues as witnesses to attest
that I was NOT rude when I approached them! 
