Often when discussing the issue of the possibility of the transmission of infectious diseases through Holy Communion, anecdotal evidence at best is presented, though usually it is more about speculations and personal beliefs. However, since the late 19th century there have been numerous scientific studies that actually give us hard scientific evidence. Most of these studies have been done in Anglican, Methodist and Lutheran churches with their debate of many decades regarding the use of the common communion cup. Using the common cup is similar to using a common spoon by Orthodox Christians. However, with the Orthodox practice, it can be added that after each communicant receives communion the priest dips the spoon in warmed wine before communicating the Holy Gifts again, which can serve as a disinfectant; this important factor is not determined in the conclusions of the studies below. Also, for those Orthodox Christians who argue for the miraculous properties of the Holy Gifts, the studies below should eliminate this factor and examines it by its physical properties alone. It is only on this basis that conclusions can be drawn. As far as I know, no such study has been done with the Orthodox practice, which should be considered.
1. The Journal of Infectious Diseases. William Burrows and Elizabeth S. Hemmens. 1943 Nov-Dec;73(3): 180-190. Survival of Bacteria on the Silver Communion Cup.
"Evidence is presented which indicates that bacteria swabbed on the polished surface of the silver chalice die off rapidly. Experiments on the transmission of test organisms from one person to another by common use of the chalice showed that approximately 0.001% of the organisms are transferred even under the most favorable conditions; when conditions approximated those of actual use, no transmission could be detected. Only small numbers of bacteria from the normal mouth could be recovered from the chalice immediately after its use by 4 persons. It is concluded that in practice the silver communion cup is not an important vector of infectious disease."
2. The Journal of Hygiene. Betty C. Hobbs, Jill A. Knowlden and Anne White. 1967 Mar;65(1):37-48. Experiments on the Communion Cup.
"The results of our work are in general agreement with those of previous workers, and show that the organisms deposited on the rim of the communion cup are not destroyed within a short time - 5 sec. as an average - elapsing between the partaking of the sacrament by each successive communicant. It must therefore be admitted that the common communion cup may serve as a means of transmitting infection. Reasons are given, however, for believing that the risk of transmission is very small, and probably much smaller than that of contracting infection by other methods in any gathering of people. Such risk as there is could be greatly diminished by use of a purificator for wiping the cup between each communicant, and could be abolished completely by substituting individual cups or by the practice of intinction."
3. Journal of Infection. Gill ON. 1988 Jan;16(1):3-23. The Hazard of Infection From the Shared Communion Cup.
"No episode of disease attributable to the shared communion cup has ever been reported. Currently available data do not provide any support for suggesting that the practice of sharing a common communion cup should be abandoned because it might spread infection."
4. Journal of Environmental Health. Anne LaGrange Loving. 1995 Jul-Aug;58(1):24-28. A Controlled Study on Intinction: A safer alternative method for receiving Holy Communion.
"This study investigated the risks involved with intinction, an alternative to sipping from the common cup in which the parishioner dips the bread into the wine and consumes both elements conjointly. These findings were compared to those of previous investigators who tested the hazards of sipping from a common communion cup. It seems that intinction does not eliminate all risk of infection, but it does reduce it over that of sipping from a common communion cup. The cleanliness of the minister's hands appears to be a significant factor."
5. Journal of Environmental Health. Anne LaGrange Loving and Lisa F. Wolf. 1997 Jul-Aug;60(1):6-10. The Effects of Receiving Holy Communion on Health.
"This detailed survey of 681 individuals compares illness rates among the following groups: those who receive communion; those who go to church but do not receive communion; and individuals who do not attend Christian services. In addition to supplying demographics information, participants answered detailed questions regarding respiratory, intestinal, skin, systemic, and other illnesses; physician consultations; and medications. Respondents also reported church attendance and participation in Holy Communion every week for 10 weeks. No significant difference in health was found among these groups, indicating that receiving Holy Communion as often as daily does not increase one's risk of infection."
6. American Journal of Infection Control. 1998 Oct;26(5). Risk of Infectious Disease Transmission from a Common Communion Cup.
"Within the CDC, the consensus of the National Center for Infectious Diseases and the National Center for Human Immunodeficiency Virus, Sexually Transmitted Diseases, and Tuberculosis is that a theoretic risk of transmitting infectious diseases by using a common communion cup exists, but that the risk is so small that it is undetectable. The CDC has not been called on to investigate any episodes or outbreaks of infectious diseases that have been allegedly linked to the use of a common communion cup.... In summary, the risk for infectious disease transmission by a common communion cup is very low, and appropriate safeguards-that is, wiping the interior and exterior rim between communicants, use of care to rotate the cloth during use, and use of a clean cloth for each service-would further diminish this risk. In addition, churches may wish to consider advising their congregations that sharing the communion cup is discouraged if a person has an active respiratory infection (ie, cold or flu) or moist or open sores on their lips (eg, herpes)."