With the Summer Olympics in Rio de Janeiro, Brazil now underway and an unprecedented travel warning issued last week in Miami, Florida by the Centers for Disease Control and Prevention (CDC)—public awareness and concern over the Zika virus has likely hit an all-time high.
While the World Health Organization, the CDC, and national ministries of health have continued their significant and coordinated efforts to better understand, track and contain this mosquito-borne epidemic, it remains a public health threat—primarily to pregnant women through its association with severe birth defects.
To date, local transmission of Zika has been reported in 65 countries (since 2015). Here in the U.S., all but four states have now reported cases of the virus, the vast majority coming from travel to other countries where Zika is actively circulating.
Elizabeth Talbot, MD, an associate professor of medicine at Geisel School of Medicine, who specializes in infectious disease and international health at Dartmouth-Hitchcock and also serves as New Hampshire’s deputy state epidemiologist, shares the latest on what the scientific and medical communities are learning about Zika.
Q: Prior to the start of the Games, some voiced the concern that Rio might pose a high risk for athletes and visitors and serve as a mechanism for spreading the epidemic—do you share those concerns?
Talbot: Risk is decreasing compared to several months ago. Brazil is reporting a decline in cases of Zika infection, in part because it’s the dry season and there is a tremendous effort being made to reduce the vector. And, there’s so much going on at the Olympics to help keep athletes and visitors safe and to educate them so that they can protect themselves.
I’m also very reassured by some of the mathematical modeling that the CDC has done, which shows that travel for the Olympics represents a tiny fraction of the total estimated travel volumes to Zika-affected countries, and that the risk of introducing Zika to a currently uninfected area is extremely small.
So the international decision to go forward with the Games seems justified to my reading.
Q: What’s happening in Florida has been called “historic,” why?
Talbot: It’s the first time in U.S. history that the CDC has recommended that certain people not travel to a place within the U.S. borders for their health and safety. Pregnant women are encouraged not to travel to a neighborhood in north Miami, where local mosquitos are transmitting the disease.
The likely scenario is that a traveler from the epidemic settings came to this neighborhood with virus in his/her blood and then a local mosquito or mosquitos bit that person, took up some virus and then bit another person, setting off local transmission (with about 15 confirmed cases as of last week). From the beginning of the global outbreak, we have been warned this could happen—the experts are not surprised by this event and planning had been done.
They are using every tool in the armamentarium against the vector—the Aedes aegypti mosquito—including aerial spraying and cleaning up small water sources where they can breed. As intensive as these efforts have been, the vector has proven difficult to control.
Q: What are the latest recommendations and precautions from the CDC?
Talbot: First and foremost, pregnant women should not travel to areas where Zika is transmitting. Those pregnant women who live in or do travel to these areas should be tested for Zika infection, even if they have no symptoms of the virus (only 20 percent of people who contract Zika have symptoms).
Partners to pregnant women (female as well as male) who travel to endemic areas should use barrier precautions for any sexual encounter following travel to avoid sexual transmission to that pregnant woman, whether she travels or not. These precautions are for the duration of pregnancy.
For couples thinking about getting pregnant, women with Zika or who travel to areas with Zika should wait eight weeks before attempting to conceive. And men with Zika should wait six months after symptoms before they attempt pregnancy with their partner.
In general, anyone travelling to an area where the virus is circulating should be fastidious about preventing mosquito bites—that’s the best protection. Applying insect repellant (with DEET) to exposed skin, impregnating your clothing with permethrin, choosing clothes that cover as much of your body as possible, and using bed nets when you’re sleeping are all highly effective methods of preventing Zika and other mosquito-borne diseases.
Q: What progress is being made on testing and treatments for Zika?
Talbot: Right now, there are two approaches to diagnosing Zika: detecting the virus itself in blood or in urine, which is only useful within the first two weeks of infection; and antibody detection on blood, which can detect evidence of Zika disease out to 12 weeks. Clearly, we need better testing—tests that are more sensitive, can be used beyond 12 weeks after infection, and are easy to deploy in the settings that are most impacted, such as South and Central America and the Caribbean.
Currently, there is no treatment for Zika except supportive care. Efforts to develop a vaccine are underway, but may be threatened due to lack of federal funding.
Q: There have been some concerns that climate change may bring the Zika vector as far north as New Hampshire—is there any evidence that this may happen?
Talbot: We have no sustained Aedes aegypti mosquito populations in New Hampshire, and they’ve not been documented this far north. That said, we are looking closely at our mosquito populations to see if any may have the capacity to carry Zika.
In New Hampshire, we’ve tested approximately 250 persons for Zika virus and have eight confirmed cases—seven being travel-related and one being sexually transmitted. I believe our clinicians understand well the risk of travel and are staying aware of the messages to help prevent additional Zika cases here. We strongly encourage anyone planning travel to Zika-affected areas to visit a travel clinic for the most up-to-date advice for prevention of Zika and other diseases.