Only a handful of companies are continuing to invest in Ebola virus diagnostic tests, concluded a team of researchers in an analysis that tracked the availability of Ebola-specific assays in the areas most affected by the deadly pathogen. These findings underscore the need to strengthen the market for infectious diseases assays by focusing on the most reliable and accessible tests, according to the investigators.

Even with the approval of 14 new diagnostic tests for Ebola virus and assistance from international donors, health workers and organizations can’t access these tests quickly enough. On average, laboratory or health center staff wait 2 to 8 weeks to receive the tests, Kevin K. Ariën, Lieselotte Cnops, and colleagues wrote in the journal Nature. Ariën is a professor of virology and head of the virology unit at the Institute of Tropical Medicine in Antwerp, Belgium; Cnops is a postdoctoral researcher at the institute.

Such challenges have plagued the Democratic Republic of the Congo, which is facing its worst Ebola virus disease outbreak since the mid-1970s. To find out the reasons behind this supply problem, Ariën and his team queried assay manufacturers and searched their websites. “Our analysis reveals that research and scaled-up production have been sustained for only a few of the company-provided tests that were developed and approved” during the 2014-2016 outbreak in West Africa, according to the authors.

Looking at seven polymerase chain reaction (PCR)-based tests approved either by the World Health Organization or the Food and Drug Administration, Ariën and colleagues discovered that just four were immediately available to buyers—meaning that labs could receive the tests in less than 2 weeks. Those tests were: Altona’s RealStar Ebolavirus test, Roche’s LightMix Ebola Zaire test, Cepheid’s Xpert Ebola test, and Liferiver’s Ebola Real Time RT-PCR test. “For the others, we either got no responses to our online order forms or would have needed to have waited 14 weeks,” they summarized.

The authors went on to explain the unique challenges of developing an assay for such an unpredictable disease. Unlike other diseases such as malaria, which pose an ongoing health threat, viral Ebola outbreaks are sporadic and inconsistent. It’s more difficult for manufacturers to make a profit from an Ebola-specific assay, given the costs associated with developing, stockpiling, and distributing the assay versus the number of tests actually needed to contain an outbreak over a finite period.

Once the threat dissipates, so does the incentive to continue researching assays in the field. “As fears about Ebola waned at the end of the West Africa outbreak, so did public and private funds available to manufacturers,” the investigators explained.

The antidote is twofold: prioritizing among the strongest, most useful tests and developing incentives for manufacturers. Having 14 different tests in the field isn’t necessary, according to the authors. What’s needed instead are “a handful of reliable, easy-to-use PCR-based and rapid diagnostic tests that are consistently available,” with the ability to simultaneously identify pathogens that produce symptoms similar to Ebola virus disease. Some care and thought should be taken in the deployment of these tests as well. As an example, rapid tests aren’t as accurate as PCR-based tests, but are easier to use, making them a better fit in remote areas.

Donor funding and investing in surveillance programs could help encourage companies to persevere on infectious disease diagnostics, according to the authors. “Establishing national and regional surveillance programs for viral hemorrhagic fever, for example, throughout Central and West Africa would require thousands of diagnostic tests,” they suggested.

Governments and public health organizations might also consider a route taken with vaccines, purchasing a diagnostic before it’s been licensed to ensure its supply. On a more global scale, Ariën, Cnops, and colleagues urged that the Coalition for Epidemic Preparedness Innovationsin Oslo develop a program for diagnostics similar to one created for prioritizing vaccines.

“Together, these steps will help to ensure that investments made during one outbreak are not wasted. Such efforts must be sustained so that they can help people to tackle the next crisis,” the authors concluded.