A ninth-century bc relief shows Assyrian King Shalmaneser III shaking the hand of a Babylonian ruler to seal an alliance (https://www.history.com/news/what-is-the-origin-of-the-handshake). A handshake remains an integral part of our culture: 78% of patients want their physician to shake their hand, and this occurs in 83% of such encounters.Reference Semmelweis ¹

Disease transmission on hands in healthcare settings has been scientifically established since the mid-nineteenth century.Reference Makoul, Zick and Green ² Possibly the first report of influenza transmission from the hands of infected individuals was in 1919, when Lynch and Cumming wrote, “There is no question but that the average individual’s hands are highly contaminated under ordinary circumstances with his own mouth organisms, and if he be a carrier, a convalescent, or a mild unrecognized case of any of the acute infectious diseases, his hands will certainly be contaminated with the disease virus.”Reference Lynch and Cumming ³ Today, hand hygiene is the cornerstone of infection prevention programs. ⁴ However, in community and hospital settings alike, maintaining high compliance is challenging.

Gastrointestinal viruses, such as norovirus, heavily contaminate the hands of infected individuals,Reference Liu, Escudero and Jaykus ⁵ which can serve as a source of transmission.Reference Park, Williamson and DeBess ⁶ Respiratory syncytial viruses (RSVs) have variable survival on hands. The concentration of human parainfluenza rapidly falls within 10 minutes on skin, surviving for ∼1 hour.Reference Ansari, Springthorpe, Sattar, Rivard and Rahman ⁷ Under the same experimental conditions, ∼40% of an RSV inoculum survives on skin after 1 hour; 16% survives after 3 hours. Under different experimental conditions, RSVs survive 1 hour on skin.Reference Hall, Douglas and Geiman ⁸ Recent studies found that influenza viability rapidly declines on human skin. In the study by Thomas et al,Reference Thomas, Boquete-Suter, Koch, Pittet and Kaiser ⁹ influenza was detectable on a minority of individual’s hands after 30 minutes. Grayson et alReference Grayson, Melvani and Druce ¹⁰ found a rapid decline in viability, but influenza was viable on hands at 1 hour in nearly half of study participants. However, an older study found that an inoculum of influenza transferred from inoculated stainless steel to hands dropped 3-fold in 24 hours but was detectable at that time.Reference Bean, Moore, Sterner, Peterson and Gerding ¹¹ Rhinovirus survives better on hands than other viruses: 50%–100% of an initial inoculum is detectable on hands after 3 hours.Reference Reed ¹²

Fresh secretions of RSV on hands can be transferred by touching another person’s hands, after which the virus becomes undetectable on the recipient’s hands in 10 minutes.Reference Hall, Douglas and Geiman ⁸ Attempted transfer of parainfluenza and rhinovirus after drying, and then 5 seconds of hand-to-hand contact with pressure approximating a handshake, resulted in no transfer and <1% transfer of the virus, respectively.Reference Ansari, Springthorpe, Sattar, Rivard and Rahman ⁷ Rubbing dried rhinovirus-inoculated hands on another person’s hands for 15 seconds transferred the virus 78% of the time, with a mean of 17% of the initial inoculum detected on the recipient’s hands. Viral transfer occurred 83% of the time from moist rhinovirus-inoculated hands to a recipient’s hands, with a mean of 34% of the inoculum detected.Reference Reed ¹² Stroking moist inoculated hands with a recipient’s hands for 10 seconds transferred rhinovirus 71% of the time.Reference Gwaltney, Moskalski and Hendley ¹³ Although none of these experiments specifically involved handshakes, they suggest the potential transmission of respiratory viruses, particularly if the handshake occurred before the virus dried on the donor’s hands, before touching other objects (eg, wiping one’s nose and soon thereafter shaking someone’s hands), especially with rhinovirus.

Could an alternative greeting mitigate the risk of viral transfer? One study found a 4-fold reduction in bacterial transfer with a fist bump compared to handshake.Reference Ghareeb, Bourlai, Dutton and McClellan ¹⁴ Another study found bacterial transfer was reduced by 50% with a “high five” hand slap compared to a handshake and by 80%–90% with a fist bump. A strong handshake led to greater bacterial transfer.Reference Mela and Whitworth ¹⁵ However, no such studies have been published assessing viral transfer by handshake.

One group of investigators suggests banning handshakes from clinical settings,Reference Sklansky, Nadkarni and Ramirez-Avila ¹⁶ and they carried out this intervention in a neonatal ICU, which led to a measurable behavioral change.Reference Parga, Valadez, Chang, Sarin-Gulian, Holdbrooks and Sklansky ¹⁷ Replacing handshakes with fist bumps does not appear in a CDC publication of pandemic influenza community mitigation strategies,Reference Qualls, Levitt and Kanade ¹⁸ and such a strategy is not a solution for poor hand hygiene practices.Reference Fred ¹⁹ However, we struggle to gain and maintain high compliance with hand hygiene, care for ever more vulnerable patients with myriad comorbidities, particularly during winter, and we continue to be concerned about transmission of respiratory viruses and norovirus, along with the usual cadre of bacterial and fungal pathogens in healthcare settings. Thus, we should more seriously consider adopting this cultural change after a millennia of handshakes.