Scientists racing against time to contain an outbreak of a mysterious flu-like illness in a remote part of the Democratic Republic of the Congo have more to contend with than identifying its cause, as they grapple with a logistics crisis that has slowed the flow of crucial supplies.

Just reaching the epicenter of the outbreak of “Disease X” can take about 48 hours by road from the capital, Kinshasa. It’s also the rainy season there, slowing the progress of experts as well as testing kits and other medical supplies to the area in the forested country’s southwestern Kwango province.

There are also no laboratories in the province that can adequately test and diagnose the samples, therefore they need to be transported by road to Kinshasa, World Health Organization spokeswoman Margaret Harris said by phone. The agency along with Congo’s National Public Health Institute and Africa Centres for Disease Control and Prevention have dispatched crews to the region. 

“You need to really be sure of your cold chain, you really need to be sure of your transport medium, you need to be sure that you’ve sampled in the best way,” Harris said. “If it does turn out to be an unexpected pathogen, you want to have taken enough samples to understand what you’re really looking at.”

More than 400 cases of the unidentified illness have been reported since late October, with the national authorities alerted to the outbreak on December 1. Most cases are among children younger than five and emerged at a time of increased influenza circulation. Dozens have died.

For now, acute pneumonia, influenza, COVID-19, measles and malaria are considered as potential causal factors, the United Nations health agency said. At this stage, it’s also possible more than one disease is contributing to cases and deaths.

Congo, which is as big as the U.S. states of Alaska and Texas combined, is home to 10% of the world’s tropical forests, and it’s where Ebola was identified in the 1970s. Increased interaction between humans and animals has led to the spread of other diseases to people from infected rodents and bats in the region. 

War and climate crises have weakened health systems and infrastructure, adding to the strain of malaria, mpox and hemorrhagic viruses such as Ebola — and left tens of millions of Congolese on the brink of starvation. All those with the most severe “Disease X” symptoms are reported to be seriously malnourished.

The difficulties mean that many people don’t come to a facility — the number of deaths related to this illness is likely to be an undercount. They also highlight the need to strengthen surveillance and laboratory capabilities in the region, Jean Kaseya, director of Africa CDC, said in a statement. 

Even so, the mosaic of challenges have contributed to scientists in the region becoming well versed in tackling infectious diseases with limited resources.

“There are people there who are really, really good at sampling and transporting and testing under the most difficult circumstances,” Harris said.