Virus proliferates best in low humidity, lower temperatures. High humidity and temps above 22C inhibit (though doesn't stop) spread. Temps above 30C significantly hinders it. Again, just passing on what I'm reading. Not an expert (except for the spelling).
Keep your levels of vitamin D at optimum. This won't stop you getting infected, but will help fighting respiratory conditions. But don't just stuff tons of pills because you can OD and poison yourself.
Vitamin C used to boost immune system.
Do NOT drink animal urine. Scientists outside India fairly certain that's a bad move.