Patients who had been previously infected with dengue might have also developed immunity for Zika, a new study finds.
Researchers from UC Berkeley and the University of Michigan found that children who have been exposed to dengue in the past are 38 percent likely to develop symptomatic Zika compared to those who have not had the disease. The team used data from the Pediatric Dengue Cohort Study (PDCS) established in Nicaragua in 2014.
Their findings were published in the journal PLOS Medicine.
The Dengue-Zika Link
The study was conducted over worries that previous infection of dengue might exacerbate Zika. Both diseases, which are transmitted by the mosquito Aedes aegypti, cause closely similar symptoms such as fever, rashes, and joint pain.
It had previously been observed that the second infection of dengue is much more severe than the first one and, since it is closely related to Zika, the researchers wanted to see how one affects the other. Apparently, previous infections of dengue can protect children from Zika.
Dengue Immunity Protects From Zika
The study involved almost 4,000 children ages 2 to 14 years. The researchers determined how many of the children had been infected with Zika virus and how many have developed the symptomatic infection. They also looked at which of the children had previously been infected with dengue. They found that children who already got infected with dengue have lower risks of developing symptomatic Zika.
"We don't think that that dengue immunity protects from being infected, or at least it doesn't look like that is the case in our study," explained Aubree Gordon, an assistant professor of epidemiology at the University of Michigan and the lead author of the study. "However, for children who were infected with Zika, prior dengue exposure protected them from symptomatic Zika disease."
In some cases of Zika, infected patients experience neurological issues. However, most do not show symptoms.
The researchers also found that previous exposure to dengue does not affect the total number of Zika virus infections. They note that more studies are necessary in order to investigate the cross-protection between the two diseases and whether dengue immunity can protect pregnant women from giving birth to children with congenital Zika syndrome or Zika-related neurological problems.