Urine better than blood for Zika test
NEW YORK — A urine-based test for the Zika virus infection has shown to be more effective than the common blood-based one for many patients, a development that could make testing for the infection easier.
The test could potentially aid efforts to control Zika, which is mainly carried by mosquitoes, as it is expected to spread further into North America in the coming months.
“The timing is excellent,” said Dr. William Schaffner, an infectious disease expert at Vanderbilt University.
The U.S. Centers for Disease Control and Prevention issued new testing guidance Tuesday, saying the virus particles can be detected at higher levels and for a longer period of time in urine than in blood.
The new guidance will make it easier to test more people for the virus. Until this week, CDC offi- cials have said the best way to detect Zika virus is to test their blood. The blood is analyzed using a sophisticated lab technique that detects a germ’s genetic material.
But health officials on Tuesday reported on an analysis of 66 people in Florida who were tested for Zika using the same detection method but with both blood and urine samples.
About twice as many urine samples correctly tested positive as compared with blood samples.
What’s more, the urine test did a good job detecting the virus for two weeks after the onset of symptoms. The blood test does a good job only for about one week.
That’s an important development, Schaffner said. “There’s a much longer window for detecting the virus,” he said.
Still, the CDC recommends testing both blood and urine in the first week. It recommends a different type of blood test, one that detects a person’s immune response to the virus as opposed to the virus itself, if more than two weeks have passed since the patient’s first symptoms.
“We are not recommending to replace blood testing. We’re saying to do both,” said Dr. Marc Fischer, a CDC epidemiologist who helped write the guidelines.
Zika virus causes only a mild and brief illness, at worst, in most people. Symptoms include fever, rash, joint pain and red eyes, and they usually last no more than a week.
But in some situations, the virus has been linked to far more serious complications.