The World Health Organization has raised the public health risk from the Ebola outbreak in the Democratic Republic of the Congo.

The leading health agency raised its assessment of the public health risk from the DRC’s Ebola outbreak to “very high” at the national level, from “high” previously, while it raised the regional risk to “high” from “moderate”.

It said the global risk remains “low”.

Here’s what you need to know:

What is Ebola?

• Ebola is a severe, often fatal disease in humans.

• It is transmitted to people from wild animals and spreads in the human population through human-to-human transmission.

• The average fatality rate is around 50%, according to WHO.

• Symptoms include the abrupt onset of fever, intense weakness, muscle pain, headache and sore throat.

How many cases?

• Thee have already been 44 suspected, probable or confirmed cases of Ebola, and 23 people have died.

• The outbreak marks the DRC’s ninth epidemic since the disease was first identified in the 1970s.

What’s different this time?

• While most cases have been identified in rural areas, this outbreak has been particularly worrying because of a confirmed case in Mbandaka, a city of about 1 million people, which is connected to the capital Kinshasa by the Congo River.

• “This does change the way we need to respond,” Peter Salama, WHO’s medical emergency program head told Reuters TV in Geneva. “Overnight, Mbandaka has become the number one priority for preventing this outbreak from getting out of control.”

What is being done? 

• A vaccine is being deployed, with health workers being vaccinated first, but it normally needs to be kept 80 degrees Celsius below freezing in a humid region where daytime temperatures hover around 30.

• WHO spokesman Tarik Jasarevic told Reuters the vaccine can still be effective for up to two weeks if stored in a fridge at between 8 and 2 degrees above freezing.