expression
a cold can lead to all sorts of illnesses
Proverb warning that even a minor cold can develop into serious health problems if neglected.
風邪は万病の元だから、早めに休んだほうがいいよ。
A cold can lead to all sorts of illnesses, so you'd better rest early.
A traditional Japanese proverb. The exact origin is uncertain, but it reflects the folk wisdom that a cold weakens the body and can trigger more serious diseases.