A new blood test may extend the window of accurate detection from weeks to months after the onset of Zika infection, giving clinicians a powerful new tool to screen for Zika throughout pregnancy, a new study led by an Indian-orgin researcher suggests.

Infection with Zika virus during pregnancy raises risk for neurodevelopmental problems in the offspring, including fetal microcephaly -- a condition in which a baby's head is significantly smaller than expected -- in at least one in ten pregnancies. The blood test called ZIKV-NS2B-concat ELISA improves on existing options, providing an accurate and cost-effective means to determine whether a patient was infected, days or months after exposure, the researcher said.

"Many people infected by Zika have only mild illness, or are unable to see a clinician in the early, acute phase of infection. Our new test greatly extends the window during which an individual can be assessed with accuracy," said Nischay Mishra from the Center for Infection and Immunity (CII) at Columbia University. The blood test quickly detects up to 200 samples in four hours and the researchers anticipate its cost will be similar to other ELISA tests used in clinical settings, the researcher said.

"An affordable and accurate test for Zika virus is critical for public health," said W. Ian Lipkin, co-author of the study published in the journal mBio. To develop and evaluate the test, the researchers analysed blood samples collected from children in the Nicaraguan Pediatric Dengue Cohort Study, all of whom had previously tested positive for Zika virus.

Using a microarray, they identified a unique peptide sequence -- a short section of amino acids -- that binds with antibodies to Zika virus but not with antibodies to similar viruses like dengue, yellow fever, and Japanese encephalitis. Next, the researchers customised a low-cost testing technology called enzyme-linked immunosorbent assay (ELISA) to work with the sequence-improving on current versions of the ELISA test which use larger sections proteins that bind to the virus.