Unidentified illnesses in northwestern Congo have killed more than 50 people over the past five weeks, nearly half of them within hours after they felt sick.

The outbreaks in two distant villages in Congo's Equateur province began on Jan. 21 and include 419 cases and 53 deaths. Health officials still do not know the cause, or whether the cases in the two villages, which are separated by more than 190 kilometers (118 miles), are related. It's also unclear how the diseases are spreading, including whether they are spreading between people.

The first victims in one of the villages were children who ate a bat and died within 48 hours, the Africa office of the World Health Organization said this week. More infections were found in the other village, where at least some of the patients have malaria.

Outbreaks in two remote villages

Illnesses have been clustered in two remote villages in different health zones of Equateur province, which is 640 kilometers (398 miles) from Kinshasa.

The first outbreak began in the village of Boloko after three children ate a bat and died within 48 hours. More than two weeks later a second and larger outbreak was recorded in the village of Bomate, where more than 400 people have been sickened. According to WHO's Africa office, no links have been established between the cases in the two villages.

Dr. Serge Ngalebato, medical director of Bikoro Hospital, a regional monitoring center, and one of the government experts deployed to respond to the outbreak, says the situations in the two villages are somewhat different.

"The first one with a lot of deaths, that we continue to investigate because it's an unusual situation, (and) in the second episode that we're dealing with, we see a lot of the cases of malaria," said Ngalebato.

The WHO Africa office said the quick progression from sickness to death in Boloko is a key concern, along with the high number of deaths in Bomate.

What are the symptoms?

Congo's Ministry of Health said about 80% of the patients share similar symptoms including fever, chills, body aches and diarrhea.

While these symptoms can be caused by many common infections, health officials initially feared the symptoms and the quick deaths of some of the victims could also be a sign of a hemorrhagic fever such as Ebola, which was also linked to an infected animal.

However, Ebola and similar diseases including Marburg have been ruled out after more than a dozen samples were collected and tested in the capital of Kinshasa.

The WHO said it is investigating a number of possible causes, including malaria, viral hemorrhagic fever, food or water poisoning, typhoid fever and meningitis.

What is being done in response?

Congo's government says experts have been sent to the villages since Feb. 14, mainly to help investigate the cases and slow the spread.

Ngalebato said patients have been responding to treatments that target the different symptoms.

The remote location of the villages has hindered access to patients while the weak health care infrastructure has made it difficult to carry out surveillance and manage patients. Such challenges are common in disease outbreaks in Congo. In December, an unknown illness killed dozens.

In the latest outbreaks, several victims died before experts could even reach them, Ngalebato said.

There needs to be urgent action "to accelerate laboratory investigations, improve case management and isolation capacities, and strengthen surveillance and risk communication," the WHO Africa office has said.

The United States has been the largest bilateral donor to Congo's health sector and supported the training of hundreds of field epidemiologists to help detect and control diseases across the vast country. The outbreaks were detected as the Trump administration put a freeze on foreign aid during a 90-day review.

Is there a link to Congo's forests?

There have long been concerns about diseases jumping from animals to humans in places where people regularly eat wild animals. The number of such outbreaks in Africa has surged by more than 60% in the last decade, the WHO said in 2022.

Experts say this might be what is happening in Congo, which is home to about 60% of the forests in the Congo Basin, home to the largest expanse of tropical forest on Earth.

"All these viruses are viruses that have reservoirs in the forest. And so, as long as we have these forests, we will always have a few epidemics with viruses which will mutate," said Gabriel Nsakala, a professor of public health at Congo's National Pedagogical University, who previously worked at the Congolese health ministry on Ebola and coronavirus response programs.