Question: "We Orthodox Christians Commune with the same spoon. What about the transmission of germs and diseases? I think germs were discovered in the 17th century. Before that, illnesses were attributed to demons."
The big question here is what do we really believe about the Eucharist. If we really believe that it is the body and blood of Christ, we shouldn't worry about it.
There is an illustrative instance in the life of St. John of Shanghai:
"Vladyka's constant attention to self-mortification had its root in the fear of God, which he possessed in the tradition of the ancient Church and of Holy Russia. The following incident, told by O. Skopichenko and confirmed by many from Shanghai, well illustrates his daring, unshakable faith in Christ. "Mrs. Menshikova was bitten by a mad dog. The injections against rabies she either refused to take or took carelessly… And then she came down with this terrible disease. Bishop John found out about it and came to the dying woman. He gave her Holy Communion, but just then she began having one of the fits of this disease; she began to foam at the mouth, and at the same time she spit out the Holy Gifts which she had just received. The Holy Sacrament cannot be thrown out. So, Vladyka picked up and put in his mouth the Holy Gifts vomited by the sick woman. Those who were with him exclaimed: `Vladyka, what are you doing! Rabies is terribly contagious!' But Vladyka peacefully answered: `Nothing will happen; these are the Holy Gifts.' And indeed nothing did happen."
Even if you take the nature of the Eucharist out of the equation, scientists who have examined the question say that the risk of getting an infection from a gold or silver chalice with wine in it is very low... and they are examining those churches that have the laity drink directly from the chalice, whereas we use a spoon. Also, if illnesses could be passed on through the Eucharist, the clergy should be perpetually ill, because after everyone else has communed, they consume the rest of the gifts, but there has been no history of such things. If you are a believer, you shouldn't be concerned. If you are not a believer, you shouldn't take communion at all, because then, according to St. Paul, you may in fact become ill as a result of your unworthily partaking of the Eucharist (1 Corinthians 11:29-31).
As for the claim that in the ancient world, they thought demons were the cause of all illnesses, this is simply not the case, as is evident from the Gospels, which always distinguishes between those who were ill and those who were demonized. If you take Matthew 8:1-16 for example, you have a leper cleansed (1-4), and there is no mention of demons. Then you have the healing of the centurion's servant (5-13), and again there is no mention of demons. Then you have the healing St. Peter's mother-in-law (14-15), who was sick with a fever, and so clearly had some sort of an infection, and yet again there is no mention of demons. In verse 16 it says that they brought to Christ many who were demonized, and he cast out the spirits with a word. In Matthew 4:24, just before the sermon on the mount, we are told "and they brought to Him all sick people who were afflicted with various diseases and torments, and those who were demon-possessed, epileptics, and paralytics; and He healed them." The demonized are only one category among all the others that are listed. So there is simply no basis for the statement that people in the ancient world thought that illnesses were all causes by demons.
