New portable Ebola detector is 1000x more sensitive than standard tests
It starts with chills, aches and pains, feeling more tired than usual. Over the course of a week, these symptoms intensify: Red eyes, unexplained hemorrhaging and bleeding.
Ebola virus disease, though typically rare, has devastated communities in sub-Saharan Africa during outbreaks. As recently as February 2021, the Democratic Republic of Congo announced its 12th Ebola outbreak. The North Kivu province is bracing itself for another emergency situation like the outbreak that ran from 2018 to 2020; 3,470 cases were reported and 2,287 lost their lives.
The disease, first discovered in the 1970s, is caused by Zaire ebolavirus, a subset of Ebola viruses known to affect humans. It’s transmitted through direct contact with the blood, body fluids and tissues of infected people and animals. The virus is also known to persist in certain body fluids even after recovery from the illness.
Once inside the body, the virus ravages the immune system and destroys organs. Infection causes a sharp dip in the cells involved in blood clotting; as a result, infected individuals expereince severe, uncontrollable hemorrhaging. At this stage, the chance of survival is around 20 percent.
According to the experts, managing outbreaks and improving these bleak survival statistics is possible through early and effective testing. Ebola disease patients are highly contagious, so the earlier a positive diagnosis is made, the sooner the patient (and those they have had contact with) can be isolated.
Additionally, early interventions can be life-saving — treating patients with antibody-based Ebola therapeutics sooner can slash the fatality rate from 80 to just 10 percent.
However, in practice, early interventions are a major challenge. Firstly, clinically diagnosing infections is extremely difficult as the early symptoms of Ebola disease (fever, headache, feeling lethargic) mirror a multitude of other common conditions, like influenza or malaria, for instance.
Secondly, the current gold standard polymerase chain reaction (PCR) test requires specialized equipment and trained personnel to perform it — both of which are usually difficult to come by in the regions affected by outbreaks. These PCR-based tests are too expensive and take too long to yield results; by then the patient has likely transmitted the virus to others.
To address these issues, scientists have explored the possibility of using lateral flow type assays, similar to the principle that powers over-the-counter pregnancy tests. While these check the boxes of cost effectiveness and speed, the payoff is that they are considerably less sensitive. This means those in the earlier phases of infection can get a false negative readout.
“We’ve put the lateral flow assay to shame, sensitivity wise.”
Regaining control of Ebola outbreaks with the D4
Now, Duke University researchers have made a massive breakthrough. They have created a highly sensitive portable diagnostic device that detects Ebola virus infections and is 1000 times more sensitive than existing tests. Additionally, the new test delivers the results a full day earlier than the PCR assay.
This innovation, called the D4 test, taps into the best of both worlds, leveraging the advantages of both the PCR and lateral flow assays. The D4 quickly and accurately detects a protein produced by the virus early on during infection called the secreted glycoprotein, or sGP.
“Prior studies suggested that Ebola virus produces secreted glycoprotein at high levels early in infection to act as a decoy and distract the immune system while the virus replicates and binds to the host cells,” said Cassio Fontes, one of the engineers who worked on the project.
“We thought that if we could detect that, we could help facilitate earlier diagnosis, containment, and treatment during [an] Ebola outbreak.”
The D4 works using a hand-held detector called the D4Scope, which is powered by batteries and uses off-the-shelf components that can be replaced easily in the field. A drop of blood from the patient is applied to the chip (roughly half the size of a credit card), and any sGPs in the sample bind to antibodies on the device, emitting a fluorescent glow.
This has been a significant breakthrough in the field of Ebola diagnostics, says Fontes: “We’ve put the lateral flow assay to shame, sensitivity wise.”
“This is exciting because by understanding the biology of this virus, we’ve shown that there may be a target to look for where immunoassays like the D4 can outperform the PCR. It’s really breaking new ground.”