Disease X: What to know about an unknown threat emerging in Africa

StudyFinds first examined the potential threat of “Disease X” in January of 2024. It was the name for a possible future pandemic. It was an idea. No actual disease existed. Now, Disease X has a form and a face, causing illness and death.

Officials from the Democratic Republic of the Congo (DRC) have reported an outbreak of a previously unknown illness. Since late October, it has sickened 376 people. Seventy-nine have died, a mortality rate of 21%. For reference, influenza had a mortality rate of just 1.8 per 100,000 people in the U.S. in 2022. They are calling this outbreak “Disease X.”

The symptoms are those of a typical respiratory infection, like influenza – fever/chills, cough, trouble breathing, stuffy or runny nose, headache, and fatigue. Disease X patients may also be anemic.

It isn’t known if this particular Disease X is the next global disaster or a self-contained occurrence. Intense work is underway to determine its features, and some key points remain to be determined.

Here are 5 factors doctors look at when new diseases arrive:

Severity

Early in the outbreak of a new disease, usually only severe cases are detectable — they trigger officials to investigate. Therefore, early reports tend to detect the worst end of the disease’s spectrum.

Prevalence

Prevalence is the number of cases present at a given time. It is probable that the true number of cases is far higher. Cases with no or mild symptoms don’t get a physician’s attention. That means reports typically underestimate the number of cases and overestimate the severity of typical cases of the new disease.

Cause

A new mysterious illness is often assumed to be a microbe such as a virus, bacteria, or parasite. What’s unclear, however, is if the infection (if it is an infection) is from a non-human source (contaminated water or food, animals) or if it is spread by human-to-human contact.

For example, in 2021, 66 children in Gambia died after receiving toxic cough syrup. All the children had similar respiratory symptoms, but it was two toxic, glycol-type chemicals in the cough syrup that killed them. A new disease can’t be assumed to be a spreading microbe. A plethora of possible origins must be investigated.

Spread

The mechanism and ease of spread must be determined. COVID-19 spreads between people by way of air droplets. A person at the peak level of virus shedding, in a small, crowded room, could infect a dozen people in minutes.

Epidemiology

This is the study and analysis of the distribution and patterns of disease conditions in a defined population, including risk assessment and preventive measures. If 79 older people in Los Angeles die from a new disease in a month, that’s a 2% increase in mortality in older people. If 79 teenagers die, it’s a 100% increase in mortality among teenagers. Demographics – the characteristics of a population and groups within it – are vital elements for understanding illness behavior.

When discussing Disease X: Watch the language!

Jeremy Faust, MD, an emergency medicine physician and public health expert based in Boston, issued a strong caution to watch the language used when delivering news both among scientists and to the public:

“Since October 24, 2024, a disease of still unknown origin has been raging in Kwango province,” officials in the DRC write in an official press release.

“I wondered what was meant by raging, because to me, that word implies ‘spreading like wildfire.’ But the press release was initially written in French and translated to English. So, I found the original version and discovered that the French word used there was sévit. To me, that verb implied severity of illness, rather than speed of spread, but my French is admittedly mediocre. However, I’ve since confirmed with native French speakers that my impression was right. The word should have been translated differently—something closer to: ‘has been severely affecting people in Kwango province,’” Dr. Faust says in a media release.

“I also happened to notice that the entire English version was created using Google Translate. I know because I pasted the French text into the app and got a nearly verbatim readout back. Look, the DRC has a lot of expertise in dealing with outbreaks and I respect their abilities on the medicine and epidemiology. But with the world hanging on every word, perhaps officials could do better than Google Translate. Maybe the WHO could help them out here.”

A final word

What I hope you take from this information is an appreciation for the complexity and difficulty of determining the origin of a disease, understanding its characteristics, and predicting its behavior. I liken it to trying to find a needle in a haystack in an active volcano. That would be easier; at least you know what you’re looking for!

Most of the time, when scientists don’t have answers for the public, it’s because they don’t have the answers. It isn’t a lack of transparency or deception. When the latest news contradicts previous news, it’s usually because doctors have achieved a greater understanding.

Don’t be swayed by dramatic language. You can follow the numbers and the principles of discovery. We are used to demanding instant, complete, and accurate information. In many cases, it just doesn’t work that way, and our expectations can be unrealistic.

What can you do? Live a healthy lifestyle. As I’ve said before, achieve and maintain a healthy weight. Eat a healthy diet. Exercise. Cultivate gratitude. Don’t smoke. Limit alcohol. Have fun. Give of your time, resources, and heart.