Basic Study
Copyright ©The Author(s) 2020. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Hepatol. Oct 27, 2020; 12(10): 775-791
Published online Oct 27, 2020. doi: 10.4254/wjh.v12.i10.775
Hepatitis B virus detected in paper currencies in a densely populated city of India: A plausible source of horizontal transmission?
Palashpriya Das, Ruchi Supekar, Ritika Chatterjee, Subrata Roy, Anisa Ghosh, Subhajit Biswas
Palashpriya Das, Ruchi Supekar, Ritika Chatterjee, Subrata Roy, Anisa Ghosh, Infectious Diseases and Immunology Division, Council of Scientific and Industrial Research-Indian Institute of Chemical Biology, Kolkata PIN-700032, West Bengal, India
Subhajit Biswas, Infectious Diseases & Immunology Division, Indian Institute of Chemical Biology (Council of Scientific and Industrial Research), Kolkata 700032, West Bengal, India
Author contributions: Biswas S and Das P conceptualized, designed and executed the present work and wrote the manuscript; Supekar R contributed substantially to the virology experiments and in writing of the manuscript; Chatterjee R, Roy S and Ghosh A took part in collecting the samples for this study and also conducted experiments; Das P and Supekar R contributed equally and are joint first authors; all authors have read and approved the final manuscript.
Supported by Institutional Grant by Council of Scientific and Industrial Research-Indian Institute of Chemical Biology, Kolkata, No. MLP-118
Institutional review board statement: The study was reviewed and approved by the Council of Scientific and Industrial Research-Indian Institute of Chemical Biology Institutional Ethical Committee on Human Subjects and Council of Scientific and Industrial Research-Indian Institute of Chemical Biology Biological Safety Committee. This work involved no use of human subjects or human clinical materials.
Conflict-of-interest statement: The authors declare that they have no conflict of interest.
Data sharing statement: No additional data are available.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Subhajit Biswas, DVSc, PhD, Associate Professor, Senior Researcher, Infectious Diseases & Immunology Division, Indian Institute of Chemical Biology (Council of Scientific and Industrial Research), 4 Raja S.C. Mullick Road, Jadavpur, Kolkata 700032, West Bengal, India. subhajit.biswas@iicb.res.in
Received: April 27, 2020
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
Processing time: 179 Days and 16.2 Hours
ARTICLE HIGHLIGHTS
Research background

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.

Research motivation

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.

Research objectives

To investigate whether paper currency can serve as a plausible mode of horizontal transmission of HBV infection in areas of high population density.

Research methods

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.

Research results

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).

Research conclusions

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.

Research perspectives

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.