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The Dire Need For A Rapid Diagnostic Ebola Test In West Africa

The size and spread of this Ebola epidemic is simply unprecedented. The largest previous Ebola outbreak occurred in 1976 in Zaire: 318 confirmed cases and 280 deaths, but the current outbreak in West Africa has exceeded 4,400 cases with 2,300 deaths and growing. According to WHO estimates more than 20,000 more cases will occur before containment is achieved.

I, and many others, have written about the need for more resources and healthcare infrastructure. Hopefully the U.S. commitment of 1700 beds, training of 500 healthcare workers and 400,000 home treatment kits will offer much needed help and reduce the mortality rate from 50%.

But stemming the tide of this epidemic will not happen with only the commitment the President has made. Treating the sick is imperative, but as the number of cases grows exponentially, we have to take a closer look at why – we are failing at contact mapping and containment, and for three very good reasons.

First, there are cultural barriers to containment such as distrust of Western medicine, commitment to local burial practices, and a lingering disbelief that the virus exists. These barriers prevent containment procedures from being implemented and sanitary burials from being practiced.

Second, there is fear of the disease and what identification and isolation means. “Virus hunters,” public health workers skilled in contact mapping of exposures, are having a difficult time finding the sick because of the fear. People hide, change their address, and have even thrown rocks at aid workers. People do not want to be isolated and taken away from their families to wait out the incubation period and possibly die alone in makeshift clinic far from home.

Finally, we do not have a way of rapidly identifying the virus in the field. Current practice for fever in countries like West Africa is to rule out and treat the things that are more common, easily identified and more easily treated with the assumption that if the patient does not improve, a viral hemorrhagic fever is the diagnosis of exclusion. In West Africa, malaria or bacterial infections are the more likely more treatable diseases, so the practice is to rule out malaria and possibly use empiric antibiotics before assuming Ebola.

We have rapid detection tests (RDTs) for malaria that can and are being used in the field. The problem is the sensitivity and specificity are not adequate to definitively diagnose malaria. And even given this practice of diagnostic rule out, the truth remains that a negative test for malaria does not necessarily mean a positive test for Ebola and visa versa. We need diagnostics that are more definitive.

There are many types of tests for Ebola. Isolating the virus provides the most sensitive and specific diagnosis, but requires transport of biohazard material to a BSL-4 lab, of which there are few in the world. Alternatively there are reverse transcription polymerase chain reaction (RT-PCR) and quantitative PCR, which are both very sensitive and specific, but again require a lab. Newer tests include antigen and antibody identification using ELISA, and a nanoparticle microscopy system termed the Single Particle Interferometric Reflectance Imaging Sensor (SP-IRIS), which can digitally identify virons based on size. (ACS Nano. 2014 Jun 24;8(6):6047-55.)

There have been improvements in diagnostic ability in Sierra Leone that have improved care immensely, but all of these tests must be performed in a lab and that lab may not be local. It could take days to get results back. We need a test we can deploy rapidly in the field and have results in under an hour.

A very rapid test would be game-changing for Ebola. Let’s look at triage in a clinic. Everyone comes in the front door together and waits together. Most people have a fever, but they aren’t sure why. Most likely, it’s another endemic infection like malaria, typhoid or shigella. An RDT could quickly identify patients needing quarantine from those who do not. The benefit here is threefold: fast and early quarantine to separate patients at risk for infecting others making the rest of the hospital safer; replacing fear and anticipation with knowledge; and a more efficient use of quarantine resources because they are saved for people with known Ebola infections.

An RDT would also allow healthcare workers to confidently come to work knowing they are not infected. It would also prevent unnecessary quarantine of these most-needed personnel for the 21 day incubation period.

The same would hold true for exposed individuals. Given the lack of clinics and isolation units, public health workers are offering more home-based care. This requires isolation of people in their homes for up to three weeks.  A RDT would allow appropriate use of those resources.

An RTD could also be used at borders and airports for health officials to safely allow or restrict access from a country with a known outbreak, enabling the delivery of much-needed supplies, workers, and resources safely.

Finally, when this outbreak is contained, having an RDT would help more quickly identify new outbreaks in the future, facilitating early containment and guiding the use of prophylactic drugs, like Zmab, if available.

I want to impress upon you this is not conjecture. The reasons above make logical sense, but experts can also use mathematical modeling studies to show the effect of adequate containment versus rapid detection. Containment is certainly effective and has worked during all outbreaks in the past, but diagnostics either on site, off site, for all febrile patients or even just healthcare works can make a significant impact on the size of an outbreak.

An RDT—a new test or an adaptation of what we have—would not only be a massive step towards controlling this outbreak, I think it is the only step that will ultimately prevent this tragic epidemic from becoming a pandemic.


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