There is no district in Sierra Leone which is not affected by the Ebola virus, officials have said.

The news came as two people in Koinadugu, the last district free from the virus, contracted the disease.

"It was the only place we are counting on where you can go and breathe a sigh of relief and to know that now in the whole country no district is safe, is heartrending," John Caulker, the executive director of Fambul Tok, a group that worked to prevent Ebola from entering Koinadugu, told news agency AP.

"Now we will increase our activities in the district and take the necessary measures to make sure the area is safe and it does not spread."

Sierra Leone country profile

Official name: Republic of Sierra Leone

Capital: Freetown

Official language: English

President: Ernest Bai Koroma

Population: 6.092 million

Major ethnic groups: Temne 30%, Mende 30%, Limba 8%, Kono 5%

Religions: Muslims 60%, indigenous beliefs 30%, Christian 10%

Life expectancy: 45/46 (WHO statistics)

Physicians Density: 0.016 physicians/1,000 population

Hospital Bed Density: 0.4%

Health expenditures: 13.1% of GDP

Sierra Leone is one of the west Africa countries most affected by the virus outbreak, which has killed at least 4,500 people since last January.

In the nation, at least 1,200 people have died after contracting the disease and some 3,000 have been infected, of whom 425 only last week.

Ebola is transmitted by contact with infected bodily fluids and its symptoms include fever, diarrhoea, vomiting and body aches.

The virus is also widely present in Liberia and Guinea.

The US Centers for Disease Control and Prevention (CDC) warned that if no effective measures were taken to stop the outbreak, between 550,000 and 1.4 million people could contract the Ebola virus by January 2015 in Sierra Leone and Liberia alone.

Nigeria was also hit by the disease and at least nine people died there. However, the country has not reported any new case and could be declared Ebola-free by the end of the month.

According to the World Health Organization, around £614m is needed to prevent the outbreak from turning into a human catastrophe.

WHO also assured people that the deadly disease is not airborne following recent speculation.