5,021 infections and 2,378 deaths had been registered as of Sunday, reports the AP news agency. This means a mortality rate of just over 47 percent. The undercount is also believed to be large.
The ongoing outbreak has infected and killed people at a faster rate than any previous Ebola outbreak. Compared with the largest outbreak to date, in West Africa from 2014 to 2016, the dreaded disease is now spreading three times faster.
"The situation is very difficult, but people are working day and night to try to control this outbreak," WHO doctor Thierno Baldé told reporters in Geneva on Tuesday.
Went under the radar
The outbreak is caused by the bundibugyo variant, for which there is currently no vaccine or specific treatment. However, two new vaccines, developed rapidly, are currently being tested in humans.
The virus, which causes hemorrhagic fever, is believed to have begun spreading several months before Congo-Kinshasa confirmed the outbreak in May.
Because of the unusual virus variant, early cases went under the radar or were misdiagnosed - early bundibugyo often causes symptoms similar to malaria and other common diseases, according to studies.
Reduced aid
The virus response is being hampered by decades of unrest in mineral-rich eastern Congo, where the disease is primarily spreading. Hundreds of thousands have been displaced by the conflict, with various armed groups fighting for control of the vast natural resources.
Skepticism toward authorities and healthcare, as well as widespread disinformation, pose additional challenges.
In addition, cuts in aid from the outside world - not least the United States - have hit Congo-Kinshasa hard. In July, the World Health Organization (WHO) said it had received less than half of the funding needed to tackle the Ebola outbreak.
Ebola virus is an RNA virus that causes hemorrhagic fever. There are six variants of Ebola virus - four of which cause disease in humans.
The virus variant bundibugyo is behind the current outbreak in Congo-Kinshasa. There are no vaccines or specific treatments for it, but development is underway.
Ebola virus is transmitted between people through bodily fluids. Sexual transmission also occurs. The illness develops quickly with flu-like symptoms such as high fever, headache, sore throat, stomach and intestinal symptoms and muscle pain. Toward the end of the illness, bleeding can occur on the skin and in internal organs.
Mortality rates are often estimated to be as high as 50-90 percent in outbreaks in affected African countries. With access to adequate intensive care, mortality rates are significantly lower.
Source: WHO, Swedish Public Health Agency
