I believe the best preventive maintenance when it comes to getting sick or contracting contagion is isolation and cleanliness. To accomplish this, every Prepper should have a huge stock of Human Waste Contamination Bags, heavy duty garbage bags, boxes of sterile latex gloves and sterile surgical masks. If there is a Bug-In situation where the power is down and there’s no running water, disposing of human waste will become a big sanitary issue quick, not prepared to deal with it can be the x-factor to sickness and disease. The isolation factor may be a bit easier to deal with in a pandemic scenario, don’t open the door, to anyone. Maybe easier said than done.