The Marburg virus, an Ebola-like bug that has killed 112 people in Angola's northern province of Uige, has reached the capital, Luanda, officials say.
The symptoms of the disease are similar to those of the Ebola virus
Its new victims in Luanda are a teenage boy and an Italian doctor, both of whom were recently in Uige.
Four other cases of the disease have been diagnosed in Luanda.
UN and aid agency officials are working with the Angolan government to contain the Marburg virus, which causes fever, vomiting and severe bleeding.
The virus was first identified in 1967 among laboratory workers in Europe who had been working with monkeys.
Senior health ministry official Filomeno Fortes told the BBC that all of the six people in Luanda infected with Marburg had come from Uige.
The health authorities have formed a commission to prevent the spread of the disease in Luanda and ensure that all available doctors are prepared to deal with the virus.
According to the World Heath Organization (WHO), three-quarters of the virus' victims have been children.
The disease was first reported in the region in October last year.
Experts from the WHO, the US and from medical charity Medecins Sans Frontieres are in Uige to work on ways to contain the epidemic.
Carlos Alberto, an Angolan health ministry spokesman, told the AFP news agency the situation "is bad, very bad".
Setting up quarantine rooms where people with suspected cases of the disease could be isolated from other patients was a priority, he said.
The European Union announced on Thursday that it will give $650,000 (£348,000) to fight the disease.
The early stages of the disease are marked by diarrhoea, stomach pains, nausea and vomiting.
As it develops, patients can experience chest pains, severe internal bleeding and eventually, death.