A cheap and accurate saliva test for Covid-19 which gives a result in just one hour has been devised by scientisrs.
The simple device, which costs as little as £1.50, is as accurate as current methods and can identify the different coronavirus variants and strains, scientists say.
The test can be 3D printed and could revolutionise coronavirus treatment and monitoring.
Dr Xiao Tan of Massachusetts General Hospital in the US, a lead scientist involved in the device's creation, said: "Our goal was to create an entirely self contained diagnostic that requires no other equipment."
"Essentially the patient spits into this device, and then you push down a plunger and you get an answer an hour later."
The device uses a gene editing tool called Sherlock that generates a fluorescent signal.
Senior author Professor James Collins, of Massachusetts Institute of Technology (MIT), said: "We demonstrated our platform can be programmed to detect new variants that emerge, and that we could repurpose it quite quickly.
"In this study, we targeted the UK, South African and Brazilian variants, but you could readily adapt the diagnostic platform to address the Delta variant and other ones that are emerging."
It is quicker and less invasive than PCR tests which require nasal swabs and take longer.
In June, the Delta variant caused infections to spike in the UK once more, delaying lockdown relaxations.
The portable device, called miSHERLOCK, allows users to test themselves at home - with no extra instrumentation needed.
Results can be read and verified by an accompanying smartphone app inside 60 minutes.
In tests of saliva samples from 27 Covid patients and 21 healthy peers miSHERLOCK was 96 and 95 percent correct, respectively.
It was also effective across a range of viral concentrations in healthy human saliva that had been spiked with the Alpha, Beta and Gamma variants.
Dr Helena de Puig, also from MIT and involved in creating the test, said: "miSHERLOCK eliminates the need to transport patient samples to a centralised testing location and greatly simplifies the sample preparation steps, giving patients and doctors a faster, more accurate picture of individual and community health, which is critical during an evolving pandemic."
It was designed to have up to four modules that each look for specific bits of DNA, called RNA, in Covid strains.
A new program for Delta should be straightforward - or any others that could make Covid more infectious. It was not widespread at the time of the study.
Co first author Dr Rose Lee, a paediatrician at Boston Children's Hospital, said: "Simple things that used to be ubiquitous in the hospital, like nasopharyngeal swabs, were suddenly hard to get, so routine sample processing procedures were disrupted, which is a big problem in a pandemic setting.
"Our team's motivation for this project was to eliminate these bottlenecks and provide accurate diagnostics for Covid-19 with less reliance on global supply chains, and could also accurately detect the variants that were starting to emerge."
The tool will also be useful in remote health care centres without easy access to PCR testing or genetic sequencing of Covid variants.
Dr de Puig added: "The ability to detect and track these variants is essential to effective public health."