Health officials in the Democratic Republic of Congo began worrying about possible Ebola cases in mid-April. Deaths in the northeastern part of the country that seemed like they may have been caused by the deadly virus prompted officials to take samples. They then sent them to the lab in Bunia.
"The first samples were tested on April 30th," says Jean-Jaques Muyembe, general director of INRB, DRC's national biomedical research center. The lab ran the samples on GeneXpert, a machine that automates the process of detecting specific bits of viral DNA. The results came back negative for Ebola. So did more samples a couple of weeks later.
Eventually, officials sent samples hundreds of miles away to Kinshasa for more specialized testing.
Those turned up positive for Ebola.
The problem was that GeneXpert, the machine that forms the backbone of DRC's Ebola surveillance, couldn't detect the rare species that was circulating, says Muyembe. So it was mid-May before officials rang the alarm bell and declared an outbreak of Ebola Bundibugyo.
That month-long delay allowed the outbreak to grow into one of the largest Ebola outbreaks ever. Suspected cases ballooned, to over 1,100, as labs struggled to keep up with incoming samples.
"The initial response has been pretty significantly hampered by the lack of appropriate diagnostics on the ground," says Caia Dominicus, senior technical adviser for the independent non-profit International Pandemic Preparedness Secretariat. If officials can't test in a timely manner, they can't get patients to isolate and prevent the virus from spreading, she says.
The response has caught up since then, at least somewhat.
"Diagnostic capacity has improved significantly from where we were three and a half weeks ago," says Abdirahman Mahamud, who directs health emergency alert and response operations at the World Health Organization. The backlog of cases has mostly disappeared, but he warns current testing capacity is not enough to keep up with an outbreak that the U.S. Centers for Disease Control and Prevention projects could reach 20,000 cases by August.
"We are very much aware we are still behind the curve," says Mahamud. "If transmission continues, both geographically, or the case load increases, we will require additional surge."
A difficult diagnostics situation
One big reason testing capacity has improved to date is a machine called RADI-One.
It's a device that can detect Bundibugyo in patient samples, and requires less training and equipment than typical lab-based testing. That ease of use allows it to be deployed in smaller clinics that are closer to the outbreak, including Mongbwalu, the mining town that's been heavily affected.
Currently, seven labs — and one mobile lab — are able to process tests across northeastern DRC. Larger labs, like the one in Bunia, can currently process over 100 samples per day, according to a laboratory technician. The technician requested that NPR not use their name because due to fears of losing the job for speaking to the media without authorization.
"Right now, we really don't have a backlog and the samples that arrive are analyzed right away and the turnaround time is basically one to twelve hours," says the technician.
Yap Boum, a senior official at Africa CDC, said on a press call Wednesday that Africa CDC is working with WHO and DRC health officials to have 50 RADI-One testing machines by the end of June.
But more will likely be needed, says Dominicus, and "there just aren't that many machines available." WHO is in talks with the small South Korean manufacturer, KH Medical, to get more, but that'll take time. There are other tests that could be deployed, but "they're not the traditional systems that have been used, so there's a necessity to train staff."
Lab-based testing has another inherent limitation — the space between the patient and the lab.
"Sample transport is a major bottleneck. It can take days, some areas are almost completely inaccessible," says Dominicus. Add in ongoing conflict, population displacement and community mistrust make for "a much more difficult diagnostics situation," she says.
The faster the test, the faster the response
One tool that could improve that situation is rapid tests, akin to the kind that became widely used during COVID. A pinprick of blood placed on a thin strip of paper could give results in minutes, as opposed to hours or days.
"The faster you detect someone's positive, the faster you can actually isolate them and stop them from spreading it onwards," says Abraar Karan, an infectious disease physician at Stanford University.
Rapid tests are less sensitive than lab-based tests, meaning they're more likely to miss positive cases. But they could still play a key role in better understanding the true scope of the outbreak and reining it in.
"We need to have a rapid test for the community," says Muyembe. In addition to testing the living, Muyembe says rapid tests could screen the dead, too. Burials in DRC often involve community members touching the deceased, which can spread the virus. Testing bodies beforehand could guide whether burial practices need safety precautions.
Despite that need, there are no rapid tests approved for Bundibugyo. There are several designed for more common species of Ebola which may work, according to lab-based research, though it's unclear how well they'd work in the field.
Developing a new Bundibugyo-specific test could take a couple of months, says Robert Garry, a microbiologist at Tulane University. "I think they could be scaled up fairly quickly. It's not a complicated technology."
Ranu Dhillon, a global health physician who advised Guinea on the 2014 Ebola outbreak thinks it's worth it, as developing therapeutics or vaccines would take even longer.
"Validating [existing tests] or having some sense of its performance characteristics could be done relatively quickly," he says. Patient samples coming into labs for traditional testing could be simultaneously evaluated on these rapid tests, he says, to see how they compare.
Scaling up both lab-based and rapid tests will take significant investment. Often diagnostics are overlooked, compared with vaccines or therapeutics, says Dominicus, of IPPS. "It's underfunded, but they give us the information we need to make key decisions," she says. "Without them we're flying blind."
Bundibugyo is rare, but not unheard of. If appropriate diagnostics had been in place before this outbreak, Dominicus says it may not have gotten so bad. "That delay in diagnostic ability set the response back."
Copyright 2026 NPR