The World Health Organization (WHO) on Wednesday reported 128 new Ebola cases and 56 deaths in West Africa in the two days to August 11, raising the death toll from the worst ever outbreak of the disease to 1,069.
Since the outbreak was identified in March, there have been a total of 1,975 confirmed, probable and suspected Ebola cases in Guinea, Liberia, Sierra Leone and Nigeria, the United Nations health agency said in a statement.
Guinea-Bissau has decided to close its frontier with eastern neighbor Guinea in a bid to prevent the entry of the deadly Ebola virus, Prime Minister Domingos Simoes Pereira said.
"Guinea-Bissau has decided to close its border with Guinea-Conakry from Aug. 12 given the threat of the Ebola virus," Pereira told a news conference late on Tuesday.
The order will likely mean the closure of official road border points, but it will be difficult to police the long and porous frontier in rural areas away from formal highways.
Governments have taken a range of measures to prevent the spread of Ebola across international borders. Ivory Coast on Monday banned air travelers from the three worst-hit countries, while Ghana on Tuesday postponed the start of the academic year for at least two weeks at universities and colleges to allow screening measures to be put in place.
Scientists studying the lethal Ebola virus say they have found how it blocks and disables the body's ability to battle infections in a discovery that should help the search for potential cures and vaccines.
A group of scientists in the United States found that Ebola carries a protein called VP24 that interferes with a molecule called interferon, which is vital to the immune response.
"One of the key reasons that Ebola virus is so deadly is because it disrupts the body's immune response to the infection," said Chris Basler of the Icahn School of Medicine at Mount Sinai, New York, who worked on the study.
"Figuring out how VP24 promotes this disruption will suggest new ways to defeat the virus."
The team, lead by Gaya Amarasinghe from Washington University School of Medicine, found that VP24 works by stopping something called "transcription factor STAT1" - which carries interferon's antiviral message - from entering the nucleus of a cell and initiating an immune response.
"This study shows just how nefarious the Ebola virus can be," said Ben Neuman, a virologist at Britain's university of Reading who was not directly involved in this study.
"Ebola virus carries a small tool that intercepts the cell's distress signals, and when this happens, it disables some of the most useful machinery that our bodies have for fighting Ebola. That leaves the body with only crude defenses that are less effective at stopping the virus, and end up causing much of the damage that can eventually lead to death."
There are no proven treatments or vaccines to prevent Ebola, although several biotech companies and research teams have potential drugs in development.
Amarasingh's team, whose work was published in the journal Cell on Wednesday, said understanding how Ebola disarms immune defenses will be crucial in the development of new treatments.
A World Health Organization-convened panel of experts said on Tuesday that patients infected with Ebola in the West African outbreak could be offered experimental drugs.
The WHO's panel of medical ethicists said several drugs had passed the laboratory and animal study phases of development and should be fast-tracked into clinical trials and made available for compassionate use.