Congo is facing one of its worst Ebola outbreaks. Here is a simple guide to what is happening and what it means.

What happened? Ebola was declared in eastern Congo on May 15. The outbreak has grown into one of the fastest-spreading on record.

How bad is it? More than 4,000 people have died out of about 8,300 cases. That is a very high death toll for a single outbreak.

Why is it hard to stop? Fighting around displacement camps is blocking health workers. Contact tracing and safe burials are difficult in conflict zones.

How does Ebola spread? Through contact with the body fluids of a sick person. It does not spread through the air.

What can be done? Early treatment improves survival. Vaccines exist for some Ebola strains. Health agencies are asking for safe access to affected areas.

Health workers wear full protective gear when treating patients. Safe burial practices are critical because the virus spreads through body fluids. Getting accurate information to villages is a major part of the response.