Coronavirus is believed to live on surfaces eg mouthpiece/sax/case for up to 48 to 72 hours and able to infect and add to the viral load of an already infected person. It is advisable to daily clean these surfaces and wash swabs to prevent adding to any infection.
Symptoms are virus load dependent: the more virus you are infected with potentially the more severe the symptoms.
People over 60 (mortality rate 15% vs 2% for younger people) and those with diabetes, heart/respiratory issues, high blood pressure, smokers are at greater risk.
The virus does its damage primarily at night in the lungs. Before going to bed UK health authorities have recommended washing face and hands with soap/disinfectant including 1cm into nostrils.
Source: Guardian newspaper reporting on UK advice.