The best defence against pathogenic diseases is a healthy, well functioning immune system.
Antibiotics are not effective for killing viruses. Therefore it is important to maintain healthy immunity in order to defend the body from viruses.
Healthy immunity is neither over-active or under-active. An over-active immune response can cause damage to the body and subsequent health issues. And an under-active immune response can leave the body wide open to viral attack with very little defence against any harmful pathogenic intruders.
Fear can be activated in people due to the media hype that ramps into full flight when there is a viral outbreak such as the recent Coronavirus. Your best defence against diseases like this is healthy immunity. Fear itself can have a detrimental effect on the immune system and health in general. If you maintain a healthy strong constitution and good immunity, your chances of defending yourself against viral diseases increases exponentially.