It is deadly and indiscriminate. And it is killing children across northern Uganda and South Sudan.
But I'm not talking about Joseph Kony's Lord's Resistance Army which, despite its sudden brush with global infamy, has not been seriously active inside Uganda for some six years.
I'm referring instead to a mysterious disease that I first encountered in the region in 2003. It is called Nodding Syndrome, and I was shocked to discover this week that nearly a decade since it was first detected, almost no progress has been made in identifying, treating or containing the disease.
Nodding Syndrome targets children exclusively, causing its victims to spasm uncontrollably and eventually to waste away and die. Many thousands of children are believed to be affected.
Scott Dowell - an American doctor I was in contact with in Asia where he was involved in the global battle against bird flu - is now helping the Ugandan authorities to fight Nodding Syndrome.
"It's frustrating not knowing the cause. I was hopeful for a quick answer when we first started studying the disease in 2009," he told me, on the phone from the Centers for Disease Control and Prevention (CDC) in Atlanta, USA.
Instead, like several other neurological disorders, Nodding Syndrome remains a complete mystery. "It could take a while to crack this," he admitted.
Initially, the CDC suspected it might be a psychogenic episode - something like mass hysteria. But brain scans quickly confirmed that they were dealing with a disease that causes measurable brain atrophy.
Has the outside world been slow to investigate? It is fair to assume that if a disease were killing children in Europe with such brutal efficiency, more attention would have been paid to it by now.
The World Health Organization, Unicef and the Ugandan Health Ministry are closely involved, but a Ugandan official in the north of the country, William Oyet, expressed concern to me that "the number of cases is increasing".
Dr Dowell says he cannot speak for what happened before 2009, but insists that Nodding Syndrome is now "high on the short list of about half a dozen" mystery diseases that the CDC is targeting.
"We'd really like to get to the bottom of this… because it's got a big impact on public health. It's hugely important to the children and families affected.
"It's also interesting from a scientific point of view - the fact that we can't figure it out. And thirdly, we are kind of hooked. We've worked with the population over a couple of years and so we're really committed to these communities," he said.
The CDC has confirmed 194 cases, but has heard credible reports of "many thousands" more affected children.
Unlike bird flu, Nodding Syndrome shows no indication of being transmitted from person to person, so "we don't have the sense that it is likely to be a threat to the rest of the world in the way bird flu is", said Dr Dowell.
"We have the funding we need to do our investigations. We are pursuing a number of leads and haven't run out of leads," he said.
But when it comes to helping communities affected by the disease, Dr Dowell is less optimistic. "The affected villages… are now facing a future with large populations of disabled kids, with all the cost implications for families and communities. That part is clearly not funded."