Epidemic.
Every large deep lake is geographical.
Chickenpox affected history by killing off a large number of people. This occurred before a vaccine was invented to prevent the disease from occurring in humans.
PandemicPandemicA PandemicA pandemic is an outbreak of disease occurring worldwide or over a large geographic area.Pandemic
Peninsula
climate
Large cities
A biome
Local Area Network
People with Canavan disease typically have disproportionately large heads
That would be osteoporosis where the bones become more porous and brittle, and break much more easily. Exercise and proper diet can play a large role in helping to prevent this disease.
NCP
A large-headed turtle occurring in most seas.