Aravinda de Silva, PhD, MPH, a member of the Institute for Global Health and Infectious Diseases, has designed a new blood test to accurately diagnose dengue and Zika Viruses, to improve surveillance and advance vaccine development.
The dengue virus (DENV), which infects several hundred million people worldwide each year, is responsible for dengue fever and the more severe dengue hemorrhagic/ shock syndrome. DENV is closely related to the Zika virus (ZIKV), which can cause microcephaly in newborns and Guillain-Barré syndrome in adults. Transmitted by the same mosquito species, both flaviviruses are spreading due to global environmental and demographic changes that favor viral spread and mosquito survival.
“Individual infections and the spread of these viruses through populations can be tracked with a blood test, but because the two viruses are closely related, diagnosis can be challenging,” said Aravinda de Silva, PhD, MPH, professor of microbiology and immunology. “For example, when Zika first emerged in South America in 2015, and then spread through all countries in Latin America, it was difficult to track with existing tests because dengue infections are common in the area. This limitation impacts surveillance, preventive measures and vaccine development.”
De Silver, with Prem Lakshmanane, PhD, associate professor, and postdoctoral fellow Lindsay Dahora Hein, led a new study published in Lancet Microbe that addresses this longstanding challenge in serology—the cross-reactivity between dengue virus and Zika virus antibodies that limits accurate diagnosis and surveillance. The study was supported by cooperative research agreements and grants from the NIH and CDC.
The solution is a new multiplex assay requiring a drop of blood that simultaneously measures immune responses to a section of the virus’s outer protective layer, that differs between dengue and Zika viruses. The assay can also provide precise serological differentiation of past infections with one or both viruses, a critical need for epidemiological studies, vaccine eligibility screening, and clinical research in regions where these viruses co-circulate.
Study Design
Researchers designed a laboratory test that uses microspheres (tiny beads) to detect multiple targets simultaneously in a single sample. These small, color-coded beads were coated with viral proteins from the four dengue serotype viruses, and Zika virus, so that the assay could detect antibodies for each dengue serotype and Zika. If antibodies were present, they would bind to their matching viral proteins on the beads. A fluorescent marker then helped the team measure the bindings using a specialized machine.
The researchers tested serum samples from U.S. travelers and residents of endemic areas (Southeast Asia, Central America, and Puerto Rico) to determine their immune status using the gold-standard flavivirus focus reduction neutralization test. Using this reference panel of blood samples, they evaluated the performance of the simpler, faster and more cost-efficient multiplex assay.
Findings
For detecting past dengue infections, the multiplex assay achieved 94.9% sensitivity and 97.1% specificity. For Zika, the sensitivity reached 100% with a specificity of 97.0%, demonstrating minimal cross-reactivity even in the presence of pre-existing DENV immunity.
When tested on a second independent panel of 389 samples from Puerto Rico only, the assay maintained high performance with approximately 94% sensitivity and over 92% specificity for dengue, and similar metrics for Zika. This underscores its potential utility for pre-vaccination screening and large-scale surveillance.
Sensitivity varied (ranging from 40% to 100% for different serotypes) when differentiating primary from multitypic dengue infections, indicating there is room to further refine, to distinguish specific infection histories.
The study presents a promising new tool that combines high sensitivity, specificity, and a sample-sparing design, paving the way for enhanced flavivirus surveillance and improved diagnostic accuracy in both clinical and research settings.
UNC research assistants Izabella Castillo and Bruno Segovia-Chumbez also contributed to the study, as well as investigators from the NIH and dengue branch of the CDC.
Risk
Outbreaks of dengue and Zika, like other related infectious diseases occurring in tropical and subtropical regions, are expanding to other areas. Viral infections not only lead to hospitalizations and deaths, they affect economies due to the long periods required for victims to fully recover. Accurate diagnosis will help advance vaccine and treatment development.
According to the CDC, locally acquired dengue cases have been detected in Florida, Texas, Hawaii, Arizona, and California. The CDC also says that small outbreaks may occur because of the increased number of travel-associated cases and because the types of mosquitoes that spread dengue are present in some areas of the United States. Dengue is common in six U.S. territories and freely associated states including Puerto Rico, American Samoa, U.S. Virgin Islands, the Federated States of Micronesia, the Republic of Marshall Islands, and the Republic of Palau.
In 2015 and 2016, large outbreaks of Zika virus occurred in the Americas, resulting in an increase in travel-associated cases in US states, widespread transmission in Puerto Rico and the US Virgin Islands, and limited local transmission in Florida and Texas. In 2017, the number of reported Zika cases in the United States started to decline. A CDC map shows countries and territories with current or past transmission that are considered at risk for virus transmission.