Why is the corona virus a health crisis ?

This is due to several reasons:

A newly emerging disease which is highly infectious with a mortality rate of 1-2%

This means there is a lack of treatment currently (apart from Remdesivir and d’examen has one) which prevents you from contracting the virus.

Furthermore, even if a vaccine is produced, it is not guaranteed that there will be substantial immunity against coronavirus. As in the SARS (similar coronavirus) outbreak, antibody levels diminished after 6 months.

Coronavirus has also impeded other forms of treatment as people stay away from hospitals due to fear of infection.
This includes:
Cancer screenings
Routine operations
Reduction in A&E attendance (for stroke and heart attacks)
Decrease in childhood vaccine immunisation coverage (especially in war-torn countries and developing countries) which can result in preventable deadly outbreaks.
HIV/Malaria/Dengue Fever programmes

It is also very hard to contain. Requiring large parts of countries to go into full lockdown which can have financial impact on the economy.

Lockdowns also have a toll on the already isolated elderly community and can impact people’s mental health