KINSHASA, Congo (AP) — Over 50 individuals have tragically lost their lives to an unidentified illness in northwestern Congo, as confirmed by local healthcare professionals and the World Health Organization (WHO) on Monday.

The time frame between when symptoms first appear and death has been around 48 hours in most cases, which has raised significant concern, noted Serge Ngalebato, the medical director of Bikoro Hospital, a key monitoring facility. He expressed this worry in an interview with The Associated Press.

This latest outbreak in the Democratic Republic of Congo started on January 21, resulting in a total of 419 reported cases, with 53 fatalities.

The initial incident took place in the town of Boloko, where three children consumed a bat and subsequently showed symptoms of hemorrhagic fever, succumbing within two days.

There has been longstanding apprehension regarding zoonotic diseases in regions where wildlife is commonly consumed. The WHO reported in 2022 that such outbreaks in Africa have spiked by more than 60% over the past decade.

The second wave of this puzzling illness began in Bomate on February 9, prompting the collection of samples from 13 cases, which have been sent to the National Institute for Biomedical Research located in Kinshasa for further analysis, according to the WHO.

Testing results have confirmed that all samples are negative for Ebola and other prevalent hemorrhagic diseases such as Marburg, though some have tested positive for malaria.

In a related incident last year, a similar mysterious illness that led to numerous deaths in another region of Congo was ultimately identified as likely being related to malaria.