Right now, the second-largest Ebola outbreak in history is raging in the Democratic Republic of Congo. As of earlier this month, more than 420 cases and 240 deaths had been reported. Rapid response teams from the World Health Organization and other public health groups have been working tirelessly to contain the spread of the virus since the first patients were diagnosed in the politically unstable province of North Kivu in late summer. Yet despite the most rigorous on-the-ground intervention by care providers that is possible, given the social climate, and deployment of several experimental vaccines – authorized for human administration prior to medical regulatory agency approval under a compassionate use protocol – the incidence of Ebola has more than doubled since September.
One factor contributing to the challenge of outbreak suppression is the lack of rapid and accurate diagnostic tests. Currently, providers must draw blood from suspected patients and send the samples to a laboratory for analysis. This process takes several days, and during that time window people who are infected can continue to move through the community when they should be quarantined.
But in a potentially game-changing breakthrough, an international research team has developed a portable, battery-operated device that can detect the presence of Ebola virus particles in a small blood sample in less than 30 minutes.
Evaluations of the device, conducted in monkeys as well as in human field trials in Guinea and Senegal, showed that it correctly identified 90 percent of positive Ebola cases and only provided a 2.1 percent rate of false negatives.
Excitingly, the test also gives concurrent results for malaria and Lassa fever – two potentially fatal febrile diseases with initial symptoms similar to Ebola.
When determining the device’s diagnostic accuracy, the team used 190 samples collected from the 2014 West African Ebola outbreak, 163 malaria-positive samples, and 233 healthy controls. For malaria, the positive detection and false negative rates were 100 percent and 0.4 percent, respectively. A description of the device and full results of the human and animal studies has been published in Science Translational Medicine.
“Many infectious diseases present with common clinical symptoms, such as fever, which complicates diagnosis at the point of need,” the team wrote. “[We] developed an assay using surface-enhanced Raman scattering (SERS) nanotags to distinguish Ebola virus infections from Lassa and malaria. Although further testing is required, this assay could be useful during febrile disease outbreaks.”
The SERS approach involves directing beams of light through the blood sample and characterizing how the photons are scattered by contact with structures within the fluid. Viral particles, normal cells, and the unicellular malaria parasite all bounce light in unique ways, so a computer within the device can compare the scattering signature of each sample to pre-programmed reference signatures.
Once the swift scattering analysis and comparison is completed, the device issues a layperson-friendly results readout. And because it is compact and battery-operated, the machine can be used in rural communities and those without electricity, areas that are often the hardest hit by epidemics.
The development team hope to improve upon their technology with continued research, but note that the platform could be a boon to disease-fighting efforts in its current form.