He solved a large number of problems.

Understanding numbers is important for solving math problems.

He was bedridden with illness for several days.

I can't solve this problem because there are too many numbers.

Hand washing and wearing masks are important for the prevention of severe acute respiratory syndrome.

He is an expert in virology.

My computer got infected with a computer virus.

The Ebola virus is a very infectious virus.

The poliovirus is a virus that primarily enters the body through the mouth and destroys the nervous system.

Norovirus can be prevented by hand washing and disinfection.