Martin County officials said Thursday they aren’t yet ready to lift their dengue fever advisory, despite though the dry season has started and they haven’t seen a new case of the mosquito-borne illness in seven weeks.
The summer’s unusual outbreak sickened 22 people in Rio and Jensen Beach neighborhoods of Martin County between June 6 and Sept 12, and prompted a mosquito control effort so intense that county workers combed through people’s yards tipping over their bird baths, draining buckets and garbage can lids to stop the bothersome insects from breeding.
The effort has contained the number of cases — including one Palm Beach county resident who visited Martin County — to the Treasure Coast. Still, with increased attention from doctors and hospitals, there have been 11 dengue cases identified in Palm Beach County in travelers to and from island nations, Palm Beach County Health Department spokesman Tim O’Connor said in mid-September.
“We do plan to have the advisory continue for a little bit longer, mostly because it was such a large number of people who got infected by the virus,” said Bob Washam, Martin County’s environmental health director. “Weather conditions could change. We’d hate to end the alert before we have real clarity that it’s not going to continue.”
A September house-to-house survey in Rio and Jensen Beach neighborhoods turned up one additional case of dengue fever, and 40 inconclusive results out of nearly 400 blood samples and interviews taken. Washam said additional tests are being done by state labs and the final numbers could shift.
“We may get some of these inconclusive come back positive. It’s very likely,” Washam said. “They are going to write it up for a formal study so Florida and hopefully others can learn from this.”
Fighting the outbreak required a massive effort from the small county health department, with public health staff working 15-hour days and calling in reinforcements from other county health departments around the state, Washam said.
“I’ve been here almost 35 years, and this was the biggest thing that’s ever happened here, with a situation affecting public health,” he said. Meanwhile, he had to battle a summer surge of cyanobacteria that turned the St. Lucie River murky and toxic.
Although county officials were hesitant to call an end to the dengue fever outbreak, the statewide blood bank, OneBlood, announced Wednesday that it will again accept blood donations from Martin County residents starting today. OneBlood had suspended donations in both Martin and St. Lucie counties in mid-September, because there is no licensed test for dengue in donated blood. The St. Lucie collections resumed once it was clear the outbreak was confined to a single neighborhood in Martin County.
With no new cases since mid-September, the blood bank concluded it was now safe to resume collections, said OneBlood spokeswoman Susan Forbes.
“The time-frame is really what we’re looking at,” Forbes said. “It’s not often that you see us deciding to shut down operations, but that’s the stance we took for the safety of the blood supply.”
Based on Key West’s experience with dengue fever in 2010 and 2011 – an outbreak reappeared a year after it had seemed to pass – Washam said the health department is prepared for another bout with dengue when the rainy season starts again next spring.
“Mosquitoes do survive through the dry season,” Washam said. “When we will be gearing up and being concerned again is when the wet season starts next year. That’s when the mosquito numbers will increase again.”
Dengue is spread through the bite of a virus-carrying mosquito, but not everyone who becomes infected gets sick.
A similar community survey in Key West had found that nearly 5 percent of people in one low-lying neighborhood had become infected, even though most didn’t realize it. That information is important, because there are four sub-types of dengue. It was sub-type 1 that was found here. If someone is infected more than once, they can develop a much more severe form of dengue, one that briefly destroys the blood’s ability to clot and can lead to internal bleeding and shock.
“Hopefully it’s over for this year,” Washam said. But he wants people to keep using mosquito spray and taking steps to avoid letting water accumulate on their properties.
“I think we always need to protect ourselves from mosquito bites even if there isn’t an advisory, because there is always the chance of West Nile virus and St. Louis encephalitis in this area.”