'Mysterious' illness kills 79, sickens 376 in Congo. Here's what we know
Health officials are continuing to investigate a deadly, undiagnosed disease that has been spreading in one region of the Democratic Republic of Congo (DRC).
Nearly 400 cases have been recorded and dozens of people have died since the "mysterious infection" was reported in late October, according to the Africa Centres for Disease Control and Prevention (Africa CDC), the public health agency of the African Union.
The World Health Organization (WHO) said it is aware of the reports and is working with officials in the DRC to investigate the source of the illness.
"WHO is working with the national authorities to follow-up on reports of an unidentified disease and to understand the situation," the global health agency said in a statement to ABC News. "We have dispatched a team to the area to collect samples for laboratory investigations."
What we know about the outbreak
The disease first appeared in a remote area in the province of Kwango, in the southwestern part of the DRC on the border with Angola, according to Africa CDC.
The first case was documented on Oct. 24. Patients have been experiencing flu-like symptoms including fever, headache, coughing and difficulty breathing as well as anemia, Africa CDC said during a press briefing on Thursday.
As of Dec. 5, 376 cases and 79 deaths from the disease have been recorded, according to Africa CDC, although local health officials have told Reuters that 143 people have died from the mysterious illness.
"The striking thing about it is not only the number of people who are infected, but the proportion of people who are dying," Dr. Peter Chin-Hong, professor of medicine and infectious disease specialist at the University of California, San Francisco, told ABC News. "So far, 79 out of 376, that's like 21%, which is really striking. Of course, it is likely overestimated, because probably just the sick people are being recognized."
Most cases, or 51.8%, have occurred in children under 5 years old. This age group also has the largest number of deaths, with 17 so far, data from Africa CDC shows.
When asked to comment, Africa CDC directed ABC News to the media briefing on Thursday. "The team on the ground is working to ascertain the data. Once [we] get more information, [we] will share," an Africa CDC spokeswoman told ABC News in a statement.
Dr. William Schaffner, professor of preventive medicine at Vanderbilt University Medical Center in Nashville, told ABC News that the fact the global health agencies are aware of a disease outbreak in a remote region is a sign that global surveillance is working.
"It's really great that we that we got notice of this so that we can respond and, as we say, surveillance is the foundation for public health," Schaffner said. "You can think of surveillance as though it were a distant early warning system – a radar, if you will. You know, initially the radar is just a blip on a screen. Well, then you have to send a team out to figure out what that blip on the screen means."
What we don't know about the outbreak
Schaffner said it's "odd" to see that one of the disease's reported symptoms is anemia, a condition in which the body has a lower-than-normal number of oxygen-carrying red blood cells. He added that it's unclear if the anemia is related to the illness or is present because some patients may have anemia as a pre-existing condition. Anemia due to malnutrition or nutritional deficiencies could be another explanation, he said.
It's also unclear how many patients have experienced mild illness versus serious illness, and if there are any patients who exhibit no symptoms, according to Chin-Hong.
"What we don't know is how many people are asymptomatic or have mild symptoms? What the tempo is? Is it something that people were kind of sick for a while and then they got progressively more ill because of that?" Chin-Hong said. Tempo in this context refers to how quickly a disease progresses in an infected person.
"In most of these kinds of outbreaks like COVID or other respiratory viruses, it's usually acute, like in the order of two to three days, and that tempo makes us speculate about what kind of infection it might be," he continued. "If it's more chronic, then it could be something like a fungus or some other [unknown] disease."
Laboratory test results on five samples taken from patients "confirming the characteristics" of the disease are expected Friday or Saturday, Africa CDC Director General Dr. Jean Kaseya said during Thursday's press briefing.
Schaffner said investigations of undiagnosed illnesses can sometimes reveal that the illness is one already known to health officials, but limited testing makes it difficult to come to that conclusion.
Africa CDC said in a post on X on Friday that it took five to six weeks after the first case was reported for local authorities to alert the national government, highlighting "gaps in Africa's disease detection systems: limited surveillance, testing delays & weak lab infrastructure."
"There are many parts of the world that are still very remote and, if there are outbreaks of provocative, new infectious diseases of any kind, it may, as in this instance, take time – much more time than we would expect but it still takes time – when these areas are so remote for that information to travel up the public health chain, and a response then is initiated," Schaffner said.
Chin-Hong added that the DRC's ongoing outbreak of mpox, as well as continued conflict in the country, may have made it difficult for information to reach the national or global health agencies smoothly and quickly.
Both Schaffner and Chin-Hong said it's important for the U.S. to play a role in investigating the origins of the illness, both to support the DRC in testing and to be prepared in the event the illness spreads to the U.S.
"It's not like we're saying, 'The sky is falling', but I think it is important for us to pay attention to every one of these signals, because the world is global, and it doesn't take very long for an infection in one part of the world to go to another part of the world," Chin-Hong said.
