Diagnostic tests for the Zika virus are only reliable in the three weeks following initial infection. That is, until now. Researchers from Columbia University developed a new diagnostic test that can detect the virus in the bloodstream several months after a person is infected.
The new Zika test improvements are threefold: better accuracy, quicker results, and enhanced cost-effectiveness. Better diagnostic capabilities are particularly vital for pregnant women, whose unborn babies run the risk of neurodevelopmental problems. For example, the Zika virus can cause the development of Guillain-Barre syndrome, an autoimmune disease affecting the nervous system.
"Many people infected by Zika have only mild illness, or are unable to see a clinician in the early, acute phase of infection," explained lead author Nischay Mishra, PhD. "Our new test greatly extends the window during which an individual can be assessed with accuracy."
The Zika virus, which was first discovered in monkeys in Uganda in 1947, is transmitted through the bite of a particular species of mosquito, the same species that is responsible for spreading dengue fever and yellow fever. No vaccine or cure exists for the Zika virus.
"An affordable and accurate test for Zika virus is critical for public health," said senior author W. Ian Lipkin, MD. "Even absent symptoms of illness or evidence of birth defects, Zika may inflict long-term harm on the person infected or their offspring."
Existing molecular tests for the Zika virus can reliably detect the virus circulating in the bloodstream two to three weeks after a person is first infected. In addition to the time limitation, existing tests also run the risk of producing false positive results, as it mistakenly recognizes similar viruses such as dengue, yellow fever, and Japanese encephalitis.
The new test, “ZIKV-NS2B-concat ELISA,” overcomes the limitations of its predecessors. The test is a customized version of ELISA, which recognizes peptide sequences that uniquely bind to antibodies produced by the body in response to the Zika virus. Researchers tested the tests efficacy with a blood sample analysis, obtained from children who had previously tested positive for Zika virus via traditional methods.
The test proved to be specific, sensitive, and reliable. False positive and false negative results occurred less than five percent of the time when the test was done within the first few weeks after acute illness. Additionally, the test can accurately analyze up to 200 samples in four hours.
The present study was published in the journal mBio.
Sources: Centers for Disease Control and Prevention, World Health Organization, Columbia University’s Mailman School of Public Health