As this issue went to press, public health officials in Miami confirmed the first local cases of Zika transmission in the United States via mosquitoes.
On July 29, 2016, the state health department confirmed the first four people infected by local mosquitoes in Miami-Dade and Broward counties. As of Aug. 5, Miami had 16 cases of local transmission by mosquitoes in the same square-mile area. Statewide, Florida was also reporting a total of 351 travel-related cases and 55 infections of pregnant women. Zika virus infection has been linked to congenital microcephaly and other serious birth defects.
As public health officials continued to test people who live or work near the index cases, they found some were asymptomatic — not surprisingly, since only about 20% of those infected with Zika have the typical symptoms of fever, rash, joint pain, and red eyes. Aedes aegypti mosquitoes were found in the area, which is north of Miami in a neighborhood called Wynwood.
The popularity of the area may not bode well for Zika control, as shops and restaurants were still drawing large crowds even as the first cases were confirmed.
“It’s very popular with young people,” says Barbara Russell, RN, MPH, CIC, director of infection control at Baptist Hospital of Miami. “There are a lot of nice restaurants and people live there and, of course, work there. That’s where the concentration is right now. Our health department is telling anyone who is pregnant who lives there, works there or has been there recently to see their obstetrician or doctor and get tested.”
Incoming patients at Baptist Hospital are being asked if they have been to the local area or any of the international destinations where Zika is spreading, she tells Hospital Infection Control & Prevention. Standard precautions are sufficient to prevent transmission to other patients, but the primary message in addition to cautioning pregnant women is safe sex and avoiding attempts at conception until tested for Zika.
“Once we went through HIV, I didn’t realize I was going to be talking about safe sex again,” Russell says. “But we counsel the man and woman to wait until the test results come back — it takes a few days. Until we call you, have no sexual intercourse or use condoms.”
Healthcare workers have been briefed and educated about Zika for some time now, so there is a general sense of readiness in the hospital.
“We put out newsletters, and the chief officer of the whole system periodically sends out an email to give an update,” she says. “We have information on our website and we hold classes and do one-on-ones. We take phone calls from the community as well as the staff.”
Again, the hospital is following standard precautions, reinforcing basic barrier protection from blood exposures.
“[We are telling healthcare workers] that’s why we have needle safety devices, why you wear gloves and wear googles if you are doing anything that could create a splatter,” Russell says. “It’s the same thing we do for hepatitis C. Also, some patients are just coming in for testing; they are not sick enough to be admitted. We are really urging pregnant women to get tested so they can have peace of mind. That’s what 90% of this is about.”
Another component of IP involvement is in Zika testing, serving as a kind of liaison between the hospital and state health department.
“The way it works here in Miami-Dade County is that if somebody needs to be tested — if a doctor thinks they need to be tested or they have symptoms or whatever — we go through the health department and they have to approve the testing,” she says. “So infection control has gotten very involved in that as kind of the conduit between the doctors and the health department.”
The blood supply was affected for a couple of days, but now donations are being tested and the supply has been restored.
“They were not taking the blood for a day or two but now they have started testing the blood,” Russell says. “For several weeks, if you went to donate blood they have asked you where you traveled, and if you have just traveled to [a Zika area] they will not take your blood. Now they are starting to test the blood like they do for HIV.”
CDC Response and Recommendations
Finding persistence populations of mosquitoes in the Wynwood neighborhood, the CDC issued a travel warning for the area of transmission and dispatched an emergency response team to Miami.
“We advise pregnant women to avoid travel to this area, and pregnant women who live or work in this area and their partners to make every effort to avoid mosquito bites and prevent sexual transmission of Zika,” said CDC Director Tom Frieden, MD, at a recent CDC press conference. “This advice applies to anyone who lives in or has traveled to this area any time after June 15. That is the earliest known date that one of the cases could have been infected with Zika.”
There is concern that the Aedes aegpyti mosquitoes that commonly spread Zika are resisting eradication despite heavy spraying, he notes.
“It’s possible that the mosquitoes there are resistant to the insecticides that have been used,” Frieden said. “Second, it’s possible that there are what we call ‘cryptic’ breeding places or small amounts of standing water where mosquitoes continue to hatch.”
To that latter point, the Aedes mosquitoes need only a small amount of water to lay their eggs, meaning common flowering plants in the area like bromeliad can serve as a nest of sorts.
“Despite the daily use of spraying, the vector control experts [in Florida] were still seeing new larval mosquitoes and moderately high Aedes aegypti counts,” Frieden said. “Just to be clear, this is a really tough mosquito to control. When Key West had an outbreak of dengue a few years back, despite extensive mosquito control efforts, that outbreak continued for more than a year. It’s a demonstration of how intensive the efforts need to be to control this infection.”