To moor a boat is to:

think of it like attaching something to your boat to secure it to something that won't move so it stays put.

"Mooring refers to lassoing, tethering, tying, or otherwise securing your boat to a fixed object, such as a mooring buoy, rather than dropping an anchor to secure your vessel anywhere you fancy. You can moor your boat to a mooring buoy, dock, quay, wharf, jetty, or pier"

if you're copy and pasting use this:

Mooring is attaching your boat to a fixed object by means of lassoing, tethering, tying or another method. Typically you attach your boat to a mooring buoy, dock, quay, wharf, jetty, or pier.

Explanation:

a)   it explains that many people died because medicines and medical practices were not effective.