New Diagnostic Test Detects Previous Zika and Dengue Infections

Brazilian scientists have introduced a novel diagnostic test that can swiftly determine whether an individual has been previously infected with any of the four serotypes of the dengue virus, as well as the Zika virus. This enzyme immunoassay is akin to the ELISA method, which is widely utilized in laboratory diagnostics in Brazil. The new technology offers the potential for integration into automated systems and for use in rapid point-of-care testing.

The research was carried out at the University of São Paulo's Biomedical Sciences Institute (ICB-USP) in collaboration with the university's medical school (FM-USP) and the Federal University of West Bahia (UFOB), led by Jaime Henrique Amorim. The findings are documented in the Journal of Medical Virology.

Dengue is recognized as the most prevalent arboviral disease globally, caused by a flavivirus with four distinct serotypes (DENV-1, -2, -3, and -4). These serotypes circulate alongside at least nine other flaviviruses, including Zika (ZIKV). The similarities in the antigens of DENV and ZIKV often result in cross-reactivity, complicating accurate serological diagnosis.

To improve the assay's precision in detecting antibodies in individuals who have been previously infected--even in those showing no symptoms--the researchers utilized fragments of viral proteins, particularly a segment of DENV's envelope protein (known as EDIII), which plays a crucial role in the virus's ability to attach to human cell receptors.

The initial validation of the test was conducted using blood samples from laboratory mice intentionally infected with DENV and ZIKV. This phase confirmed the test's ability to differentiate between specific antibodies for each virus and those generated in response to all four DENV serotypes.

Subsequently, the test was validated with approximately 650 blood samples collected from individuals in São Paulo during the Brazilian Zika epidemic (2015-2017). The results indicated a sensitivity of 87.8% (minimizing false negatives) and a specificity of 91.4% (reducing false positives).

Furthermore, the researchers assessed 318 blood samples from healthy individuals with no prior dengue diagnoses in Barreiras, a city in Bahia state where DENV and other arboviruses are endemic. The analysis revealed that around 65% of these samples reacted to at least one dengue antigen, with 88 samples reacting solely to DENV-1 and 90 samples exhibiting reactions to multiple serotypes. Interestingly, only three samples tested positive for ZIKV, suggesting either a decline in ZIKV circulation in the region over recent years or a shorter duration of specific antibodies following ZIKV infection.

According to the lead researcher, the development of this test represents a significant advancement in monitoring serological immunity in populations exposed to these viruses, particularly for individuals living in endemic areas for DENV and ZIKV or those who have received dengue vaccinations.

As of early 2025, Brazil has reported 21 fatalities attributed to dengue within the first month, with a significant number occurring in São Paulo state. The recent emergence of DENV-3, which had not been observed for 17 years, has raised concerns among experts about the potential for more severe outbreaks.

Looking ahead, this diagnostic test is expected to play a vital role in identifying individuals and groups lacking immunity against the circulating DENV serotypes, thereby informing public health initiatives aimed at vector control and vaccination efforts.

The antibodies identified through this assay, primarily immunoglobulin G (IgG), are crucial for the immunity that protects against the disease, as they prevent the virus from entering human cells. This characteristic allows the test to evaluate the immunity of individuals who have been exposed to these viruses in the past, as well as those who have been vaccinated.

For ZIKV, the test will enable assessments of immunity in reproductive-age individuals and pregnant women, the primary groups at risk, without the complications arising from cross-reactivity with antibodies resulting from infections with the four DENV serotypes. This capability will facilitate preventive measures in anticipation of any resurgence of ZIKV in Brazil.