The knowledge of possible potential transmission sources of clinically relevant pathogens is crucial for infectious disease prevention. Banknotes and coins have been discussed as fomite for an indirect contact transmission because they are routinely exchanged between individuals. The handling of cash in routine businesses was hypothesized as a viral transmission vector in the covid-19 era14, and the World Health Organization (WHO) and the Centers for Disease Control (CDC) have emphasized that people should be aware and using it with safety precautions, rather than banning it.
The reliability of our sample processing protocol in an artificial setting experiment could promote the validity of true positive or true negative results in the real-world samples. The recovery Cq data from the tested banknote and coin were similar, with the exception of the Cq values from the banknote being slightly lower than those found in the coin. This suggests that there were no significant inhibitors from materials in the amplification reaction, and the lower Cq value in the tested banknote may correlate with its texture characteristics of a large and flat surface, enhancing the efficacy of swab collection. However, only the S and RdRp genes were amplified. Three primary reasons account for the explanation: (1) the quantity of positive genes is contingent upon the viral quantity in the sample and the integrity of the retrieved RNA. It implies that if the sample containing SARS-CoV-2 RNA had a very low concentration and was not intact, the test would fail to detect any target genes, (2) the absence of N gene detection could be attributed to a mismatch of the primer and probe, and (3) the analytical sensitivity of the N gene using the Allplex SARS-CoV-2/FluA/FluB/RSV kit was 95.51% (88.89–98.76), which is lower than that of the S gene, which is at 98.88% (93.90–99.97) and the RdRp gene which is at 97.75% (92.12–99.73) as demonstrated by Kim et al.28. That prior investigation identified 5 positive outcomes from 90 positive samples exhibiting amplified targets absent of the N gene28. However, the results from the positive control showed the successful detection of all three target genes, demonstrating that the master mix used in this test was properly prepared and capable of detecting the N gene, RdRp gene, and S gene. The positive control serves as a synthetic material used to validate the effectiveness of the reagent kit in amplifying each target gene.
This study identified SARS-CoV-2 in 2% (2/100) of pooled samples collected from two distinct markets within the Thawi Wattana district, and rotavirus A in 2% (2/100) of samples from two different markets located in the Bang Sue and Min Buri districts. Similarly, SARS-CoV-2 positive samples were identified in the absence of the N gene. From the beginning of week 24 to the middle of week 29 in 2024 of our study periods, the Department of Disease Control (DDC) of the Ministry of Public Health (MoPH) in Thailand reported an average of 133–465 confirmed SARS-CoV-2 cases per day, while the prevalence of confirmed rotavirus cases ranged from 26.32 to 27.12%, ranking second after norovirus GII cases, which were reported at 36.44–36.84% (https://ddc.moph.go.th/). Nevertheless, the DDC reports did not provide the category data between infected cases and locations. Consequently, we were unable to elucidate the correlation between the positive findings and the case incidence in the detected area.
Furthermore, another limitation of this investigation was the comparison of the positive viral detection rate with prior studies, as the data available was extremely few for both viruses. The research conducted by Newey et al.29 found no SARS-CoV-2 RNA in any banknotes and coins collected from Utah, USA, using LAMP assay targeting ORF1ab and S genes. Conversely, the study by Akter et al.11 reported a positive detection rate of 7.29% (31/425) for Bangladesh banknotes using real-time RT-PCR. In addition, to our knowledge, we have reported for the first time the positive detection rate of currency contaminated with rotavirus. The factors associated with result variations may be influenced by the occurrence of cases at the study sites, hygienic measures, material and surface of sample types, virus strain, various physical parameters, and sensitivity of detection methods30. Our chosen study sites are excellent fresh food markets accredited by the Department of Internal Trade (DIT), Ministry of Commerce, Thailand. Stringent hygiene requirements are implemented in these markets to mitigate the risk of contamination.
Interestingly, only banknotes have tested positive detection. This may be explained by the difference in viral stability between on banknote and coin material and surfaces. Most Thai banknotes are still made from 100% cotton fiber paper, except for the 20 baht note that has been recently changed from paper to polymer to improve the quality and make it more durable31. Riddell et al.32 demonstrated that SARS-CoV-2 remains stable on paper and polymer banknotes for a minimum of 28 days at 20 °C. Kramer et al.33 have demonstrated that many gastrointestinal viruses, including rotavirus, can persist on environmental inanimate objects for approximately 2 months. On the other hand, all Thai baht coins are made of various types of metal alloys depending on each value, including nickel-clad iron, nickel-copper, and bimetallic between Cupronickel and Aluminium Bronze34. The numerous viruses can be effectively eradicated within 4 h on copper and other alloy surfaces35,36,37. The antiviral effect may be due to the release of copper ions from metal surface, which results in the killing process38. Furthermore, coins represent a lower risk than banknotes due to their significantly reduced exposed surface areas39.
Asymptomatic or mildly symptomatic individuals can act as a possible source of currency contamination by handling cash with contaminated hands that poses a risk of viral transmission. The virions may infect another individual by being transferred via a finger from contact with contaminated currency to a face mucous membrane or through ingestion39. Conversely, the cause of money contamination may arise not from interaction with infected individuals, whether vendors or buyers, but from food that is contaminated within the processing chain that is not entirely eradicated. We presented the linked findings between the identified virus and the type of shop. The SARS-CoV-2 RNA samples have yielded positive results at the fish shop, whereas the rotavirus A RNA samples have tested positive at the pork and poultry shop. Prior reports have documented the detection of SARS-CoV-2 on frozen aquatic food species and their products, including packaging materials and storage environments40. Additionally, the rotavirus was previously identified in pork and chicken meat cuts available in retail markets41,42,43. Virus contamination from contaminated foods to cash may occur through hand contact between them in the absence of proper hygienic precautions. The detection of viable virus is crucial for demonstrating potential ability for viral transmission and infectivity. Unfortunately, our study faces a limitation with viral culture because it must be conducted in a Biosafety Level 3 (BSL3) facility, which is not generally available at our institute, and it requires expert technicians for the virus culture. Nonetheless, all positive Cq values obtained in this study were above 35 cycles. It is possible that this is a viral remnant rather than infectious particles, which are at a reduced risk of causing viral transmission and infection. Schijven et al.39 demonstrated a minimal risk of banknotes serving as fomites for SARS-CoV-2 in cash transactions under real-world circumstances. Additionally, the successful infection requires high viral loads, like those found in saliva and cough specimens of infected patient at levels of > 1010 copies/ml or > 106 PFU/ml44,45.
The isolated SARS-CoV-2 in the present investigation was classified as JN.1 sub-variants of the Omicron variant based on the genetic analysis and phylogenetic tree construction. We have also analyzed nucleotide and amino acid sequence identities of our virus strain SARS-CoV-2/Environment/THA/Banknote-P55/2024 against multiple known SARS-CoV-2 variants by using Sequence Identity Matrix application in BioEdit program. The result demonstrated that our identified virus was closely related to SARS-CoV-2 variant of Omicron GRA (JN.1) by showing 100.0% nucleotide identity, and showed the 100% amino acid identity to all SARS-CoV-2 variants. In January 2024, Thailand experienced a significant increase in the number of hospitalizations and fatalities as a result of the JN.1 sub-variant of the Omicron covid-19 variant46. The WHO has recently designated a novel strain, JN.1, as a variant of interest (VOI), emphasizing its potential importance in the ongoing virus control effort. Despite the fact that existing antibodies offer some protection, variant JN.1 is characterized by unique mutations and rapid transmission. Nevertheless, current vaccines demonstrate substantial potential47. Furthermore, scientists are expressing worries regarding the potential for the JN.1 variant of SARS-CoV-2 to specifically target the intestinal tracts of individuals in addition to the respiratory tract48.
Rotavirus A is the most prevalent species and primarily infects humans, particularly young infants, resulting in acute gastroenteritis49. Based on the phylogenetic tree data, we identified rotavirus A genotype G8 from our positive sample. The circulating strains of rotavirus in Thailand have been changed over time, more than twelve years period from 2008 to 2020, and the G8 genotype was one of predominant strains found in pediatric patients with diarrhea, especially from 2018 to 2020. Therefore, the G8 genotype became the most prevalent genotype49. Jiang et al.50 indicated that children infected with G9 and G8 genotypes exhibited more severe symptoms, whereas the occurrence of fever and electrolyte imbalance did not significantly vary among the other genotypes. Moreover, the rotavirus A genotype G8 has been identified in swine globally, although it is not the predominant strain49. Due to the prolonged persistence of rotavirus on environmental surfaces33, there will be an increased risk of viral transmission and infection.
In conclusion, although banknotes and coins can act as carriers for virus transmission, the danger of causing illness appears to be minimal due to the low contamination rate. Nevertheless, it is imperative to practice caution when handling cash and coins. Advancements in cashless and contactless transactions through online banking and digital wallets should be actively sought wherever possible.
