I don't think elderberries have to be an Israeli variety to be effective. I have read other studies that suggest that elderberries are effective against most viruses. I ran out and picked wild elderberries and made jars of jam for when we get sick (and it is wonderful just for it's taste). Next year, I want to make elderberry wine for the same reason.
Elderberries grow wild all over the country, and ripen here (California)in August through early October.
I've had luck with elderberry preventing a cold if I take it right at the first symptom, but if I'm already sick it doesn't do a thing.