I learned to receive Communion on the tongue, which was the custom for past generations. Aids is transferred through bodily fluids (mucous membranes). The priest cannot deny anybody to receive Communion on the tongue, but it must be unpleasant for the priest, the recipient and the person next in line. Is it not a question of hygiene if the priest inadvertently touches the tongue or lips of a person receiving in this way and then carries on to the next person?
From what I can gather, there seems to be no medical evidence that HIV, the virus that causes Aids, can spread from an infected person to an uninfected person by simple saliva. There would have to be infected blood in the saliva before that could happen. The risk is therefore low.
Yet people today are very alert to the need for cleanliness and hygiene in their contacts with other people and things. We are urged to wash our hands regularly because of the viruses and germs in the environment. So, you are right. It can be a question of hygiene.
An interesting case arose in 2001 when the Archbishop of Hobart, Tasmania, asked his priests to stop offering the chalice for communion and urged the people to receive the host in the hand. This was because Tasmania was plagued by the deadly Meningococcal disease at the time, and precautions were needed because of saliva clinging to the chalice and to the priest’s fingers. The archbishop could not stop people from receiving Communion on the tongue, which remains the norm of the Latin Rite. Apparently, Communion in the hand became immediately more popular.
The Southern African bishops have allowed Communion in the hand for many years and, as far as one can estimate, most of us receive this way, possibly because of our fear of transmitting infections. Yet Communion on the tongue is far from fading out. Only last year in Rome, a synod of bishops on the Eucharist was concerned that Catholics were ill instructed on the need for reverence when taking the host in their hands. There was a strong lobby to stop this custom.
With care and dexterity, a minister of the Eucharist can avoid touching the lips or tongue of the communicant, but there are always the rare moist exceptions, which may not be significant. Perhaps our bishops and clergy may consider re-examining the need for hygiene AND reverence in the reception of Communion.