Published online Oct 27, 2020. doi: 10.4254/wjh.v12.i10.775
Peer-review started: April 27, 2020
First decision: August 9, 2020
Revised: August 18, 2020
Accepted: September 14, 2020
Article in press: September 14, 2020
Published online: October 27, 2020
The recent rise in the incidence of hepatitis B virus (HBV) infections in a densely populated city of eastern India prompted the search. Paper currency is widely used as a mode of transaction for various goods and services irrespective of socio-economic status among the population. Therefore, the chances of microbial contamination specifically in the currencies of lower denominations are higher. The common practice of enumerating currency notes using saliva in Indian subcontinent may be a potential source of horizontal transmission of HBV, especially if there are cuts/bruises on the oral mucous membrane or skin.
The increasing number of cases of HBV infections in eastern India served as the impetus to investigate possible presence of this virus in low denomination paper notes in a densely populated city of India such as Kolkata.
To investigate whether paper currency can serve as a plausible mode of horizontal transmission of HBV infection in areas of high population density.
HBV was detected by performing polymerase chain reactions (PCRs) on nucleic acids extracted from ultracentrifuged washings from paper currencies, followed by nucleotide sequencing for the confirmation of the presence of the virus. Hepatitis B virus surface antigen-enzyme-linked immunosorbent assay (HBsAg-ELISA) was carried on HBV DNA-positive samples to check for the detectability of HBV surface antigen. Atomic force microscopy (AFM) was used for visual confirmation of HBV particles in ultracentrifuged/immunoprecipitated samples from currency paper washings.
Out of all the currency notes screened (n = 70), 7.14% of the samples were found to be contaminated with potentially intact/viable HBV of genotype D2. Atomic force microscopy provided visual confirmation of HBV particles in ultracentrifuged/immunoprecipitated samples from currency paper washings. However, HBV isolates from the currency notes failed to be detected by hepatitis B surface antigen ELISA. Molecular analysis and enzyme immunoassays suggested that the circulating HBV are “occult” in nature (i.e. ELISA-negative but DNA-positive).
Applying saliva on fingers for counting bank notes is a common practice in the Indian subcontinent and many other countries of the world. Paper notes may be a source of “horizontal” transmission of HBV as well as other environmentally stable infectious viruses like severe acute respiratory syndrome coronavirus 2, especially if there are cuts/bruises on the oral mucous membrane or skin. However, it was practically not possible to demonstrate experimentally such transmission. Detection of potentially intact/viable and “occult” HBV on currency notes and in considerable numbers poses potential risk of silent transmission of this virus in densely populated cities like Kolkata.
Heavily used paper currency may play a potential role in transmission of infectious viruses like HBV. The present study puts forward a model of horizontal HBV transmission from infected saliva to finger to paper currencies and then from contaminated bank notes to finger to saliva of susceptible humans, especially in places where people have the habit of using saliva for counting bank notes.