Preexisting Dengue and Zika Infection May Not Reduce Secondary Health Risks

Zika virus infection while pregnant creates health risks for unborn children

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According to a new study, having a previous infection with either the Zika or dengue virus within the last year, had no apparent effect on the patient’s current clinical course of subsequent infection with the other virus.

This study’s finding published on August 1, 2019, is important in 2 aspects:

  • Given recent efforts to develop a preventive vaccine for the Zika virus,
  • And the introduction of the current dengue virus vaccine (Dengvaxia) in areas where both viruses are now co-endemic.

In this new monkey-based study published in PLOS, these University of Wisconsin-Madison researchers examined secondary Zika virus or dengue virus infections in rhesus and cynomolgus macaques that had previously been infected with the other virus.

They assessed the outcomes of secondary Zika virus or dengue virus infections by quantifying viral RNA loads, clinical and laboratory parameters, body temperature, and weight for each cohort of animals and compared them with control animals. 

These comparisons demonstrated that within 1-year of primary infection, secondary infections with either Zika virus or dengue virus were similar to primary infections and were not associated with enhanced or reduced disease severity. 

Although additional studies are needed, "Our results differ from those shown in tissue culture and immunocompromised mouse models and aligns more closely with current human epidemiological data where enhanced secondary Zika infection has not been reported after primary dengue infections,” said David O'Connor, Ph.D., with Department of Pathology and Laboratory Medicine, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin, in a related press release.

This new study’s conclusions differ from a January 2019 study, which reported ‘children with a history of prior dengue virus infection had a significantly lower risk of being symptomatic when infected by Zika virus.’

The study offers insights to vaccine producers since both the Zika virus and dengue virus are genetically and antigenically related flaviviruses that now co-circulate in much of the tropical and subtropical world.

While dengue virus has been entrenched in the Americas for decades, the emergence of locally-acquired Zika cases in Cuba, Mexico, and Puerto Rico during 2019 has increased the demand for a preventive vaccine to reduce Guillain-Barré syndrome, birth defects, and fetal loss reported by Zika-infected patients.

Additionally, the US states of California, Florida, and Utah have reported ‘international travel-related’ Zika infections in 2019.

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The Zika virus is an enveloped, positive-sense, single-stranded sRNA, arthropod-borne virus that is classified in the genus Flavivirus, family Flaviviridae, says the Centers for Disease Control and Prevention (CDC).

Many people infected with Zika virus won’t have symptoms or will only have mild symptoms. For this reason, many people might not realize they have been infected since the symptoms of Zika are similar to dengue and chikungunya viruses.

The CDC says ‘to see a healthcare provider if you develop symptoms and you live in or have recently traveled to an area with risk of Zika. Your healthcare provider may order blood or urine tests to help determine if you have Zika.’

For patients with suspected dengue or Zika virus disease, nucleic acid amplification tests are the preferred method of diagnosis. 

And, immunoglobulin M antibody testing can identify additional infections and remains an important tool for the diagnosis of these diseases. But, interpreting the test results is complicated by cross-reactivity, and determining the specific timing of infection can be difficult. 

This recommendation is especially important if you are pregnant, says the CDC.

This research was funded by grants from the United States National Institutes of Health - National Institute of Allergy and Infectious Diseases (NIH/NIAID) principally award number R01 AI116382, secondarily, R21 AI131454 (to M.T.A.).

Competing Interests: G. Young and H. Dean are employees of Takeda Vaccines, Inc. All other authors declare no conflicts of financial or personal interests.