Researchers have created a portable and fast-acting test that can distinguish Ebola infections from other fever-causing infectious diseases such as Lassa fever and malaria in around 30 minutes. The study detailing their new device was published in the 12 December issue of Science Translational Medicine.
The platform — which requires only a blood sample, pre-packaged vials, and a battery-powered reader — is designed for use in settings that lack laboratory infrastructure and electricity. Although further testing is necessary to optimize the device, it could offer a simple and less expensive diagnostic tool to accelerate the detection and management of Ebola epidemics in low-resource settings.
As one of the most dangerous infectious diseases in the world, Ebola is a massive source of concern for health officials both in sub-Saharan Africa and abroad. Most large Ebola outbreaks are caused by the Zaire subspecies of the virus, which causes symptoms ranging from fever to internal bleeding and ultimately kills 50% to 90% of infected individuals, according to the World Health Organization .
The 2014 West African Ebola outbreak, which mainly affected the countries of Guinea, Liberia and Sierra Leone, was the most widespread Ebola epidemic in history. It led to massive loss of life and significantly disrupted the economy and social fabric of the region, causing over 11,000 deaths and an estimated $53 billion in economic damages .
Furthermore, the ongoing Ebola outbreak in Congo is the second-largest in history and continues to grow, highlighting the persistent danger this disease poses to public health. Although researchers have developed an effective vaccine for Ebola, there are still significant obstacles that impede the management of epidemics.
Cases of Ebola, for instance, can be difficult to detect because they initially mimic the symptoms of other fever-causing diseases like Lassa fever and malaria, according to the study authors. These diseases require very different treatments, but patients are often misdiagnosed and are directed to the wrong treatment centers.
Ebola epidemics also tend to occur in regions that lack laboratory infrastructure and trained lab personnel, limiting the applicability of conventional diagnostics. During the 2014 outbreak, health authorities relied on a test known as RT-PCR, which was accurate but could not be adequately deployed in many areas due to these obstacles, according to the study.
"One challenge in diagnosing Ebola and other infectious diseases with similar symptoms is the lack of an easy test to identify people with these conditions that can be used in the field," said John Connor, associate professor of microbiology at the Boston University School of Medicine and senior author of the new study.
"This challenge was very evident during the 2014-2016 Ebola outbreak, where a diagnosis of Ebola infection could take days because diagnostic testing could not be easily implemented at the point of need," he said.
To address the need for a faster-acting diagnostic, the researchers developed a portable test for Ebola designed for use in remote settings. The platform, which is based on a protein detection technology known as SERS, works by adding a small sample of blood to pre-packaged vials containing dried, temperature-stable chemicals. The vial is mixed for 30 minutes before being transferred to a reader that detects light signals associated with viral particles. The reader then delivers results on whether the patient is infected with Ebola, Lassa or malaria in 30 seconds.
The scientists designed the device to meet the needs of field staff in low-resource environments, according to Connor. The vials do not need to be stored and transported at cold temperatures — a typical requirement of standard diagnostic methods. Furthermore, the readers that analyze the samples are battery-powered and can be used in areas that lack electricity, he said.
After successfully testing their device in monkey models of Ebola, the team conducted field tests in Senegal and Guinea using 190 blood samples from Ebola patients that were gathered during the 2014 outbreak, 163 samples from malaria patients and 233 samples from non-infected individuals.
The test correctly detected the presence of Ebola in 90% of the Ebola samples, compared to a detection rates ranging from 65% to 92% for other rapid diagnostic tests and a rate of 95.7% associated with a standard RT-PCR diagnostic. It also showed excellent capabilities for detecting malaria, sniffing out infections in 100% of the malaria samples.
"In this first feasibility study, our method showed good performance compared to existing laboratory tests for Ebola," said Connor. "If fully developed and commercialized, it could be more portable and less expensive than existing RT-PCR assays."
The new study is well-conducted and highly relevant, according to César Muñoz-Fontela, a researcher at the Bernhard Nocht Institute for Tropical Medicine in Hamburg, Germany. Muñoz-Fontela, who is not affiliated with the new study, said it addresses two critical gaps in Ebola care: the necessity to distinguish Ebola from other suspects and the lack of a test that does not require cold storage.
"Their test would definitely be useful to speed up the triage process and to make sure that patients with other diseases such as malaria spend less time in Ebola treatment centers," he said.
Muñoz-Fontela noted that one possible drawback could be that the assay might not identify Ebola patients who have very low amounts of virus in the blood, but said that the test should be able to detect most acute cases. He also believes upcoming versions of the test could address this limitation.
Connor stressed that his research team will perform further testing to optimize the device. He added that his team's SERS technology could help scientists develop point-of-care diagnostics for other infectious diseases, and imagines a system where authorities could "mix and match" multiple tests to respond to disease outbreaks in a variety of settings.
"Millions of people are infected with the combination of Ebola, malaria and Lassa fever, and human health would be improved greatly by widespread availability of diagnostic devices," said Lee Gehrke, a professor of microbiology and immunobiology at the MIT Institute for Medical Engineering and Science who is not affiliated with the new study. "This paper has great significance towards [achieving] that goal."