Viruses similar to the strain that causes Covid-19 can survive on clothing and transmit to other surfaces for up to 72 hours, scientists at De Montfort University Leicester (DMU) have warned.
In a study looking at how coronavirus behaves on three fabrics commonly used in the healthcare industry, researchers found that traces can remain infectious for up to three days.
Led by microbiologist Dr Katie Laird, virologist Dr Maitreyi Shivkumar and postdoctoral researcher Dr Lucy Owen, the research involved adding droplets of a model coronavirus called HCoV-OC43 – which has a very similar structure and survival pattern to that of SARS-CoV-2, which causes Covid-19 – to polyester, polycotton and 100% cotton.
The scientists then monitored the stability of the virus on each material for 72 hours.
The results showed that polyester poses the highest risk for transmission of the virus, with infectious virus still present after three days that could transfer to other surfaces. On 100% cotton, the virus lasted for 24 hours, while on polycotton, the virus only survived for six hours.
“When the pandemic first started, there was very little understanding of how long coronavirus could survive on textiles,” said Dr Katie Laird, Head of the Infectious Disease Research Group at DMU.
“Our findings show that three of the most commonly used textiles in healthcare pose a risk for transmission of the virus. If nurses and healthcare workers take their uniforms home, they could be leaving traces of the virus on other surfaces.”
Last year, in response to the pandemic, Public Health England (PHE) published guidance stating that industrial laundering should be used for healthcare worker uniforms but where it is not possible, staff should take uniforms home to be laundered.
Meanwhile, the NHS uniform and workwear guidelines state it is safe to wash healthcare workers’ uniforms at home, provided the temperature is set to at least 60°C.
Dr Laird raised concerns that the evidence that supported the above statements was mainly based on two outdated literature reviews published in 2007.
In response, she advised the government that all healthcare uniforms should be laundered in hospitals to commercial standards or by an industrial laundry.
She has since co-published an updated, fully comprehensive literature review which evaluates the risk of textiles in the transmission of disease, highlighting the need to for infection control procedures when handling contaminated healthcare textiles.
“After the literature review, the next stage of our work was to evaluate the infection control risk of washing healthcare uniforms contaminated with coronavirus,” she continued. “Once we had determined the survival rate of coronavirus on each of the textiles, we turned our attention to identifying the most reliable wash method for removing the virus.”
Using 100% cotton, the most commonly used healthcare textile, the scientists conducted a number of tests using different water temperatures and wash methods, including domestic washing machines, industrial washing machines, on-premise hospital washing machines, and an ozone (a highly reactive gas) wash system.
The results showed that the agitation and dilution effect of the water in all of the washing machines tested was enough to remove the virus.
However, when the team soiled the textiles with an artificial saliva containing the virus (to mimic the risk of spread from an infected person’s mouth), they found that domestic washing machines did not fully remove the virus and some traces survived.
It was only when they added a detergent and increased the water temperature that the virus was completely eliminated. Investigating the tolerance of the virus to heat alone, findings showed that coronavirus was stable in water up to 60°C, but was inactivated at 67°C.
Next, the team looked at the risk of cross contamination, placing clean items of clothing in the same wash as those with traces of the virus. They found all wash systems removed the virus and there was no risk of the other items being contaminated.
Dr Laird explained: “While we can see from the research that washing these materials at a high temperature, even in a domestic washing machine, does remove the virus, it does not eliminate the risk of the contaminated clothing leaving traces of coronavirus on other surfaces in the home or car before they are washed.
“We now know that the virus can survive for up to 72 hours on some textiles and that it can transfer to other surfaces too.
“This research has reinforced my recommendation that all healthcare uniforms should be washed on site at hospitals or at an industrial laundry. These wash methods are regulated and nurses and healthcare workers do not have to worry about potentially taking the virus home.”
With the support of the UK Textiles Trade Association, Dr Laird, Dr Shivkumar and Dr Owen have since shared their findings with industry experts across the UK, USA and Europe.
“The response has been very positive,” said Dr Laird. “Textile and laundry associations around the world are now implementing our key messages in their guidance for healthcare laundering, to prevent further transmission of coronavirus.”
David Stevens, CEO of Textiles Services Association UK, the trade association for the textile care services industry, said: “Going into a pandemic situation, we had the basic understanding that textiles were not among the top transmission media for coronaviruses.
“However, we really had a lack of information about the stability of these viruses in different fabric types and in different wash programmes. This resulted in several misinformation floating around and excessive recommendations for washing.
“We have considered in detail the methodologies and research practices used by Dr Laird and her team and find this research to be reliable, repeatable and reproducible. The conclusion of this work completed by DMU reinforces the vital role of contamination controls – whether it is domestic or industrial settings.”
To further the research, the team is also working on a project in collaboration with DMU’s Psychology team and University Hospitals of Leicester NHS Trust, surveying nurses and healthcare workers about their knowledge and attitudes towards washing their uniforms during the Covid-19 pandemic.