Eight more cases of Ebola have been identified in Congo, raising to 17 the number of people confirmed to have contracted the deadly illness, the World Health Organization said Tuesday.
The cases were confirmed by the Centers for Disease Control and Prevention in Atlanta, WHO spokeswoman Fadela Chaib told reporters in Geneva.
The outbreak in Congo is the first major resurgence of Ebola in years.
About 400 people have fallen ill in the affected region of Kasai Occidental over the past five months, and at least 170 people have died - though only six of those killed are confirmed to have had Ebola, Chaib said.
The fate of the eleven remaining confirmed cases is unknown, WHO spokesman Gregory Hartl said.
Some of those who have fallen ill since April have tested negative for Ebola, but positive for other diseases such as shigella - a diarrhea-like disease - or typhoid.
Two newly installed mobile laboratories provided by CDC and the National Public Health Agency of Canada will speed up diagnosis and help separate those stricken with Ebola from those with less lethal diseases, Chaib said.
The so-called "Zaire strain" of Ebola kills about 50 percent of those infected through massive blood loss, and has no cure or treatment. It is spread through direct contact with the blood or secretions of an infected person, or objects that have been contaminated with infected secretions.
Shigella and typhoid - a common disease in the region - respond to antibiotics, unlike Ebola.
Congo's last major Ebola outbreak struck in Kikwit in 1995, killing 245 people. Kikwit is about 185 miles (300 kilometers) from the site of the current outbreak.
WHO says more than 1,000 people have died of Ebola since the virus was first identified in 1976 in Sudan and Congo. Primates, hunted by many central Africans for food, can carry the virus.