ISO 18184: 2019. Determination of antiviral activity of textile products.

Test accredited in our laboratory by ENAC (Spanish National Accreditation Entity) The test is accredited in our laboratory for its performance with the viruses stated by the standard, the three viruses indicated by the EN 14476 standard for general viricidal activity (Poliovirus type 1, Adenovirus type 5 and Murine Norovirus), the virus indicated by the EN 14476 standard for the activity against enveloped viruses (Vaccinia Virus MVA, strain Ankara), and against human Coronavirus strain 229E).

The global improvement in the standard of living makes consumers look for health protective products. The increase in people´s interest in protection against epidemic diseases, which protect them in crowded places with other people, such as occurs in public transport, hospitals, nursing homes, etc., along with advances in textile product processing technology, they have allowed the development of products with protective effects for health and hygiene. The textile product with antiviral properties is the result of the development of textile technology and biotechnology. Being relatively new products, the test methods developed to evaluate their properties were developed by the manufacturers themselves, so there was no unified test method, making it difficult for consumers and manufacturers to evaluate. Antiviral textile products are textiles capable of reducing the number of infectious virus particles that it comes in contact with the surface of the textile.

This has led to the need to establish an international standard to satisfy the need raised by consumers and manufacturers that could be applied to woven fabrics, fibers, yarns, braids, etc. The ISO 18184: 2019 standard specifies test methods for determining the antiviral activity of textile products against specific viruses. Due to the individual characteristics of each of the viruses, in terms of how they are affected by products incorporated into textile products, the results of a test virus cannot be extrapolated to other viruses.

The standard lists three viruses as an example, Influenza A H3N2 virus (A/Hong Kong/8/68/H3N2), Influenza A H1N1 virus (A/PR/8/34/H1N1) and Feline Calicivirus, the first two of them of considerable susceptibility, and the third of greater resistance, but it is indicated that other viruses can be used at the request of manufacturers. In IVAMI, the viruses chosen by the clients will be used, which in turn must be selected based on the antiviral activity expected by the manufacturer, taking into account that the most resistant viruses are those without envelopes (Poliovirus, Adenovirus, Norovirus), whereas enveloped viruses are more susceptible. As an example, we indicate that the EN 14476 standard, to consider a product as general virucidal, must show activity against Poliovirus, Adenovirus and Norovirus; that if the product shows activity only against Adenovirus and Norovirus, it is considered as virucidal with limited activity (with activity against Adenovirus, Norovirus, Rotavirus and enveloped viruses); and that if the product shows activity against Vaccinia virus, it is considered active only against enveloped viruses.

The standard gives two alternative methods to quantify the number of infectious viruses, which are the plaque formation method and the TCID50 method (Infectious Units for cell culture 50%). The standard leaves up to the laboratory to decide whether to use one or the other. At IVAMI, due to experience with tests carried out according to other internationally accepted standards (EN, ASTM, ISO), the quantification of viable viruses is used using the TCID50 procedure.

In the test, tissue pieces are used, both control (without incorporated antiviral) and the product under assay with incorporated antiviral, which are sterilized in an autoclave, or otherwise by the procedure indicated by the manufacturer, which are inoculated at various points with the chosen virus suspension/s with a known TCID50 number (>107) and are maintained for a contact time of 2 hours (or up to a maximum of 24 hours) with the tissue pieces. After the contact period, the deposited viruses are eluted and the quantity of virus present is quantified. The guideline allows to calculate the antiviral efficacy value of the product of assay (Mv) and, according with, classify the product in two categories of products with a good antiviral effect (Mv between 2 and 3) or excellent antiviral effect (Mv ≥ 3). For this purpose, control of textiles without antiviral incorporated must be compared. For this reason, all the appropriate controls must be available in the test, to confirm that the tissue does not contain elements that prevent the quantification of the virus in the inoculated cell cultures, by releasing substances that decrease the susceptibility of the cell cultures to infection by the virus. On the other hand, controls should be included to know the number of viruses deposited immediately after placing them on the tissues, and controls on both the tissue without antiviral, or with antiviral without inoculating with the virus suspension/s.