A total of 1,077 suspected cases and 246 probable deaths have been recorded since the Democratic Republic of the Congo (DRC) declared its 17th Ebola outbreak on May 15, the Africa Centers for Disease Control and Prevention (Africa CDC) said on Thursday.

Eleven other countries across the continent are now at high risk of being affected, namely South Sudan, Rwanda, Kenya, Zambia, the Central African Republic, Tanzania, Ethiopia, Angola, the Republic of the Congo, Burundi and Somalia, said Jean Kaseya, Africa CDC director general, during an online press briefing.

What makes this outbreak different?

Scientists have identified six species of ebolavirus to date. Three of them are known to cause major outbreaks in humans: the Zaire, Sudan and Bundibugyo viruses.

This outbreak is caused by the Bundibugyo virus disease (BVD), a rarer Ebola strain than the Zaire strain that has driven most previous outbreaks in the DRC. It was first identified in Uganda in 2007 and has only been recorded once before in the DRC, during an outbreak in 2012.

Although the Bundibugyo virus is generally considered less lethal than the Zaire virus, experts warn that the current outbreak presents several unique challenges.

There are currently no approved vaccines or targeted therapies for BVD. The outbreak which is unfolding in eastern DRC, a region affected by insecurity and population movement, makes surveillance, contact tracing and healthcare delivery more difficult.

It further alarmed experts because transmission may have been occurring for weeks before the disease was confirmed. Early laboratory tests focused on the more common Zaire strain, delaying identification of the BVD.

How does it spread?

Fruit bats are suspected to be the natural reservoir of Ebola viruses. Humans can become infected through contact with infected animals or through direct contact with the blood, bodily fluids, secretions or excretions of infected individuals, reported the World Health Organization (WHO).

The incubation period of BVD ranges from two to 21 days. 

People are generally not considered contagious before symptoms appear. A person is believed not to get Ebola from simply being near someone or passing them in public spaces because it doesn't spread through the air, according to the United States Centers for Disease Control and Prevention.

What are the symptoms?

Patients typically develop early "dry" symptoms, including fever, fatigue, muscle pain, headache and sore throat, symptoms often resembling those of many other infectious diseases.

As the disease progresses, symptoms may include vomiting, diarrhea, abdominal pain, rash and impaired liver or kidney function. Some patients also experience neurological symptoms such as confusion.

Can it be treated?

No approved vaccine or specific antiviral treatment are currently available for BVD.

However, early supportive care, including rehydration, electrolyte management and treatment of symptoms, can significantly improve a patient's chances of survival.

Containing outbreaks also requires rapid case detection, laboratory testing, contact tracing, infection prevention measures, safe burials and community engagement.

Ebola has an average case fatality rate of around 50%, although the rate has varied significantly across outbreaks, ranging from 25% to as high as 90%, according to the WHO.

Case fatality rates in the past two BVD outbreaks, reported in Uganda and the DRC in 2007 and 2012, have ranged from approximately 30% to 50%, the WHO reported.