Previously I wrote about preventing infections when travelling using Kefir.
This is not the only big hitting defense you have. Try algae. In fact, Chorella to be exact.
The lipid profile is exactly what the immune system needs. If you combine this with other things the immune system needs at that point where you think you're going down with something, take a lot and this usually prevents it or cuts down the fever by a day or 2.
Marine sourced oils are usually what is missing in most people's diets these days. I expect this is due to our marine ape source. That is, early humans came from the sea, lived by the coast and in fact we are descended from fish and have more in common with whales than say, a cow.
This could change you're life.
Algae is the most compact bundle of nutrients I know. Very relevant for the traveller with weight limits. Spirulina is good 2. The 2 overlap in what they provide a bit but Chorella packs a little for for the wieght. This is the only thing I'll take now regularly. It's also nice fresh but of course, not really possible when travelling.