Concerns over the spread of Zika virus were elevated earlier this month when a Fresno County woman was diagnosed with the mosquito-borne illness.
Although this case and most other cases of Zika within the U.S. have been associated with travel, fear that the disease will spawn from local mosquitos is mounting, especially since parts of Fresno County have aedes aegypti mosquitos that can carry the virus.

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While the concern is valid, physicians at Valley Children’s Hospital say Central Valley residents should keep their fear in check because Zika is very rare in the U.S. and there are no confirmed cases of someone acquiring the virus from a local mosquito, though researchers in Florida suspect two cases there could be attributed to mosquitoes.
Dr. Nael Mhaissen, a pediatric infectious disease specialist at Valley Children’s, said mosquitos in the U.S. don’t currently carry the virus so in order for Zika to spread locally, a domestic mosquito would have to bite an infected person and survive long enough to bite someone else.
“The risk does not appear to be that high because you have to have a person who travels or acquires the infection somehow get bit by a mosquito, and that mosquito has to survive long enough to go find another person and bite them and give it to them and so forth,” Mhaissen said. “The mosquitos do not give the virus to other mosquitos, just to humans and animals, so the risk is low but given the scope of this infection and how prevalent it is, it might happen at some point.”
In a panel discussion held July 22, Valley Children’s physicians discussed the infectious disease, its transmission, symptoms and prevention.
Overall, panelists agreed the Zika virus shouldn’t be a huge concern for the general population as the effects of the virus are mild. Mhaissen said only 20 percent of those infected experience symptoms like fever, red eyes, joint pain, rashes, muscle pain and headaches.  
Pregnant women or women trying to conceive, however, need to take extra precautions when traveling or when their partner travels because when passed from mother to fetus, Zika appears to cause birth defects such as microcephaly, where the baby is born with an abnormally small head. Zika can also cause an expectant mother to have a miscarriage or stillbirth.
According to the Center for Disease Control, the Zika virus has caused more than 1,500 cases of birth defects worldwide since 2015, with most of the cases originating in Brazil. In the United States and its territories, several hundred pregnant women have been infected, with the largest concentration of patients in Puerto Rico.
Dr. Robert Sigman, a maternal-fetal medicine specialist, suggested pregnant women avoid traveling altogether if possible. If their spouse or partner travels, they should use precautions once they return, since the virus can be transmitted sexually from one partner to another, he added. If a women who has had Zika wishes to become pregnant, Sigman suggests waiting two to six months to conceive just to be safe.
While the birth defects caused by Zika are worrisome, Sigman said people shouldn’t be too alarmed about the virus.
“We’re not quite certain if this translates into something we should be tremendously concerned about,” Sigman said. “We can talk about any number of infectious diseases with which we have a lot of concerns about. We have viruses like H1N1. That killed 1,000 women and another 3,000 survived. It was by far a much more deadly virus than Zika, but the image (of infants with microcephaly) has propelled us to this state where everyone is asking and is concerned.”
Those who are concerned, Sigman said, should focus on prevention. The aedes aegypti mosquito bites during the day so Sigman said those going outside in the daytime should wear insect repellant with 20 percent DEET. And even though its hot, it’s also a good idea to wear long-sleeved shirts and pants.
Mhaissen said Central Valley residents should also check their yards to get rid of standing water, as those areas could be breeding grounds for the aedes aegypti mosquito. People can also invest in screens to keep mosquitos out if they leave their windows or sliding glass doors open. Closing the doors and windows altogether and running the air conditioner, while not energy efficient, is probably the best way to detract mosquitos as mosquitos thrive in the heat and don’t like cool environments.
Panel organizer Dr. Karen Dahl, vice president of quality and patient safety, said the recommendations could change if Zika spreads further.
 “As Zika virus changes in the U.S., the recommendations may change and we certainly learned that with other infectious diseases and we keep checking in with the CDC,” Dahl said. “Right now there is just a concern for travelers but that may change in the future depending on how common the disease becomes.”