Health Care

Is it Zika or dengue? New CDC guidance advises doctors to test patients for both.

Summer in South Florida brings warm weather, high humidity and mosquitoes — an ideal environment for two closely related viruses, Zika and dengue fever.

Scientists with the Centers for Disease Control and Prevention said Thursday that they want clinicians to keep both diseases in mind whenever patients present with fever, rash, and joint and muscle pain.

Zika and dengue fever have surfaced in South Florida in the past. Both are transmitted primarily by the bite of an infected Aedes aegypti mosquito, though Zika can also be transmitted by sex and through blood transfusions. And both produce similar symptoms.

“Both of them can have some pretty bad consequences but in different populations,” said Tyler Sharp, a health scientist with the CDC’s dengue branch in Puerto Rico and author of a report advising doctors and nurses to be on the lookout for both diseases.

“With Zika we mostly think, not exclusively, of pregnant women and devastating consequences to their fetuses,” he said. “With dengue, there’s risk of hemorrhage, shock and fatal outcomes in individuals of all ages.”

In this September 2016 photo, Aedes aegypti mosquitoes, which can transmit Zika and dengue fever, sit in a petri dish. The CDC advises doctors to test patients for Zika and dengue fever because of similarities in symptoms and geographic prevalence of both diseases. Felipe Dana AP

When Miami became the first city in the continental United States to report a local outbreak of Zika in summer 2016, it wasn’t easy for people to access reliable testing. But in May, the Food and Drug Administration authorized commercial marketing to consumers of the first diagnostic test for detecting Zika virus antibodies.

“That’s a big step forward,” Sharp said.

Florida’s health department has not reported a locally transmitted Zika infection since 2017 while the most recent local case of dengue fever occurred in 2018.

This year, the state reports that 21 people, including 10 in Miami-Dade, have contracted Zika while traveling outside the United States. Another 31 cases of dengue fever, including 21 in Miami-Dade, have been reported since January, also among travelers to other countries.

There is no treatment or vaccine for Zika or dengue, both of which pose threats to pregnant women and their fetuses, though in different ways.

Zika has been shown to cause birth defects, such as microcephaly and neurological problems in children born to women infected during pregnancy. Dengue is not associated with birth defects, but it can be transmitted from mother to child during the final week of pregnancy, Sharp said. Pregnant women also are at higher risk of having a more severe dengue infection than women who are not pregnant.

Daniel Chang covers health care for the Miami Herald, where he works to untangle the often irrational world of health insurance, hospitals and health policy for readers.