In endemic areas, diagnosis may be based on detection of antibody but in new introductions of disease it is preferable to detect the virus.
In one case, the tests failed to detect the virus.
So scientists continue to rely primarily on mosquito surveillance to detect the virus.
Meanwhile, both the Pasteur Institute and Gallo's team applied for patents for a test that could detect the virus.
The donor's blood was tested at death with a standard procedure that cannot detect the virus for weeks or even months after infection, Dr. Williams said.
Using standard virologic techniques, the scientists from Gabon, Germany and France said they could not detect the virus in the blood of the healthy contacts.
The agency said the H.I.V. tests now in use were highly accurate, but still could not detect the virus 100percentt of the time.
But there is no reliable test to detect the virus on surfaces, so the only way to tell whether a ship has been disinfected is to send it out again and see whether anyone gets sick.
The rapid escalation of confirmed cases of infected birds or mosquitoes, while disconcerting to the public, has brought some comfort to public health officials by proving that the surveillance system set up to detect the virus is working.
And after the onset of dengue's characteristic fever that varies widely in temperature, antibodies do not appear in significant levels for days, meaning doctors cannot use conventional blood tests to detect the virus until the worst is already over.
He said they could detect the virus in a type of white blood cell known as the T-lymphocyte, the second type of white blood cell in which scientists have detected the SARS virus.
