Blood Test For Ebola Doesn’t Catch Infection Early (NPR)
In an ideal world, health care workers returning from West Africa would get a quick blood test to prove they aren’t carrying the Ebola virus. A test like that would likely put to rest some of the anxiety surrounding these doctors, nurses and scientists.
Unfortunately, even the best blood test in the world can’t do that.
The test uses a technology called PCR, for polymerase chain reaction. It can detect extraordinarily small traces of genetic material from the Ebola virus.
But the catch is, the test is usually used on blood samples. And in the beginning, that’s not where the Ebola virus hides.
"The initial sites of replication actually are not in the blood itself — they’re mostly in tissues like spleen or liver," says Thomas Geisbert, a microbiologist at the University of Texas Medical Branch in Galveston.
Magnified 25,000 times, this digitally colorized scanning electron micrograph shows Ebola virus particles (green) budding from an infected cell (blue).