The FAO (Food and Agriculture Organization) and the WHO (World Health Organization).
This is known as congestive heart failure
There are instances
that when we are exposed to virus or bacteria, the antigen A in our body try to
fight but still we get sick, take some medication and we are then healed. Then,
another exposure to a new virus or bacteria, the antigen B reacts weakly for
our immune system do not recognized the foreign pathogen that invade the body
resulting to slight sore throat after visiting your sister at school.