As scientists continue to study the relatively novel Zika virus, researchers have found that children with a history of prior dengue infection had a significantly lower risk of being symptomatic when infected by Zika, according to a study in Nicaragua of more than 3,000 children.
Experts had worried that prior dengue infection could worsen Zika disease, but the new findings published Tuesday in the journal PLOS Medicine suggest that prior dengue immunity in children may protect against symptomatic Zika, which can cause fever, rash, joint pain and red eyes.
Zika and dengue are closely related and cause similar symptoms. Both viruses are spread primarily through the bite of an infected Aedes aegypti mosquito, though Zika can also be transmitted by sex and through blood transfusions.
There is no treatment or vaccine for Zika or dengue. But dengue virus has been entrenched in the Americas for decades, while Zika was not reported in the region until 2015. Since then, scientists have been studying Zika disease, which causes symptoms in about one of five people who are infected.
Since dengue and Zika are closely related viruses —and because a second dengue infection can sometimes be much more severe than a first dengue infection —scientists have wanted to know whether Zika following a dengue infection could be more severe.
To answer the question, researchers studied the 2016 epidemic of Zika among a group of children in Managua, many of whom had a history of dengue.
Among the 3,893 children younger than 14 who were studied, researchers estimated there were 1,356 Zika infections —560 of which were symptomatic cases —from January 2016 through February 2017. Cases were confirmed by laboratory testing.
While dengue has been reported in Florida, the disease has not been as prevalent in recent years. In November, Florida health officials confirmed the state’s first case of dengue for 2018. The infection occurred in Miami-Dade, though health officials did not identify a specific part of the county where the virus was transmitted.
Before November, the most recent local outbreak of dengue reported by the health department had occurred in 2013 in Martin County.
Zika, though more novel than dengue, became a public health emergency for Florida in 2016. In the summer of that year, Miami became the first city in the continental United States to report a local outbreak of Zika when the Centers for Disease Control and Prevention and the Florida Department of Health identified the Wynwood neighborhood as having mosquitoes that were actively spreading infection.
Pregnant women are considered to be at the greatest risk from Zika because the virus has been shown to cause microcephaly and other neurological disorders in children born to mothers infected while pregnant.