Generate an opening sentence for a journal article about the coronavirus pandemic.
The coronavirus (COVID-19) pandemic has brought unprecedented challenges, both medical and socio-economic, to societies worldwide, and has become the defining public health crisis of our time.
Complete the following task based on the instruction and optional input provided.### Instruction:
Generate an opening sentence for a journal article about the coronavirus pandemic.

### Output:
The coronavirus (COVID-19) pandemic has brought unprecedented challenges, both medical and socio-economic, to societies worldwide, and has become the defining public health crisis of our time.