Everything we know about the mystery illness that's killed over 50 people just days after feeling sick

An unidentified illness has affected hundreds of people and killed more than 50 just days after victims reported feeling sick, health experts are warning.

As of February this year, as many as 419 people have caught the mysterious illness since the outbreak began in the Democratic Republic of the Congo on January 21.

Some 53 people have also tragically died in the country's northwestern Équateur Province from the condition, some of whom passed just 48 hours after reporting symptoms, the World Health Organization (WHO) has said.

Officials in the country are now issuing a stark warning about the condition. Here's everything we know about it so far.

The WHO says it is investigating the outbreak (Thomas Fuller/SOPA Images/LightRocket via Getty Images)

What is causing the illness?

So far, the illness has spread to two remote communities in the province which are separated by more than 120 miles, reports AP.

In the first instance, the Africa office of the WHO said three children in the village of Boloko had eaten a bat carcass and died within the next two days. But 400 more cases were discovered two weeks later in the village of Bomate, where some patients also have malaria.

However, health officials are yet to determine the cause of the outbreak, and whether the cases recorded in the two areas are related.

Doctor Serge Ngalebato, medical director of Bikoro Hospital, a regional monitoring center, commented: "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."

In some cases of the deaths, children had reportedly eaten bats (Getty Images)

Why are health experts concerned?

Health pros are concerned because there's still a lot of uncertainty around the mysterious disease, including how it is spreading and if it's contagious enough to spread between people.

Alarm bells are also ringing in the WHO due to the speed in which people are dying after becoming sick, as it the sudden hike in deaths.

The unknown disease 'poses a significant public health threat', the WHO warned.

Symptoms of the mystery illness

Patients have been suffering from fever, vomiting, diarrhoea, muscle aches, headaches, and fatigue in about 80 percent of cases, the Congo’s Ministry of Health has said.

With the symptoms being so common, officials were initially concerned some of the victims contracted a hemorrhagic fever such as Ebola or Marbug, however, samples have ruled out the possibility.

The WHO said in a statement: "The exact cause remains unknown, with Ebola and Marburg already ruled out, raising concerns about a severe infectious or toxic agent.

"Key challenges include the rapid progression of the disease, with nearly half of the deaths occurring within 48 hours of symptom onset in one of the affected health zones, and an exceptionally high case fatality rate in another."

The global health body said 'urgent action' is needed as it continues to investigate other possible causes like malaria, food or water poisoning, typhoid fever, meningitis and viral hemorrhagic fever.

The illness has claimed the lives of more than 50 from two separate villages (World Health Organization)

Is the illness unique to Congo?

It's a possibility the life-threatening illness has a link to Congo's vast green landscape, specifically being home to the largest sprawl of tropical forest on the planet.

But Congo, as well as many African nations, are at particular risk of contracting diseases given the high consumption of wild animals.

Gabriel Nsakala, a professor of public health at Congo’s National Pedagogical University, said: "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."

How are officials tackling the illness?

Experts have been deployed to both villages as of February 14 to help monitor the situation and try to halt the spread.

So far, Dr Ngalebato said patients have been responded to treatments but the threat remains large considering the remote position of the villages presenting access difficulties and weak healthcare infrastructure.

To determine what the disease is, the WHO says that 'metagenomic sequencing and additional investigations are ongoing to determine the cause of illness and deaths in the two health zones.'