KINSHASA, Congo — More than 50 people have been killed by a mysterious illness that has quickly spread since late last month and infected more than 400 people in the Democratic Republic of Congo, according to health officials.

After completing dozens of lab tests, doctors and scientists so far have ruled out the deadly Ebola and Marburg viruses, and yellow fever, which have appeared infrequently in west and central Africa. Symptoms from the unknown illness typically appear within 48 hours and include weakness, fever, vomiting, and internal bleeding.

The illness was first documented on Jan. 21 after three children who reportedly consumed a bat and died within 48 hours.

So far, at least 419 people have reportedly been infected and 53 people have died from the illness.

More on the mysterious outbreak in the DRC and how Trump’s WHO withdrawal is impacting the health crisis.