Arizona state health officials confirmed the first cases of locally acquired Zika in Sonora, Mexico.
Sonora has seen travel-related Zika cases since March, but the five cases discovered in early October are the first time residents of the Mexican state have been directly infected with the disease from mosquito bites.
“Locally acquired cases are cases that are associated with a mosquito-to-human spread. That is, there is an infected mosquito that bit an individual and that individual became ill,” said Francisco Garcia, the director and chief medical officer for the Pima County Health Department.
“That’s different from a travel-related case, which is a case where someone visited an area where there is endemic transmission and became ill there,” he said.
However, these cases of Zika and the proximity of infected mosquitoes just across the border don’t pose an imminent threat to residents of Southern Arizona, said Dr. Cara Christ, director of the Arizona Department of Health Services.
“Unless if you’re traveling to that area, Arizona communities are not a current threat of local transmission,” Christ said. “Our mosquitoes do not have Zika at this point.”
A news story in the Mexican newspaper El Universal on Oct. 15, however, said there was one more confirmed locally acquired Zika case in Sonora than officials here reported.
There are currently 44 travel-associated Zika cases confirmed statewide, eight of which are in Pima County. Overall, there are 3,878 travel-associated cases across the country and 137 locally acquired cases in Florida, according to the Centers for Disease Control and Prevention.
Pima County has taken steps to ramp up its efforts to track the type of mosquito that carries the Zika virus, known as the Aedes ageypti mosquito.
“We have tripled the amount of mosquito surveillance we’ve been doing in Pima County since the beginning of the season (in February),” Garcia said.
“We’ve deployed three times as many traps as we’ve ever had in this county to see what kinds of mosquitoes are in circulation,” he said. “We have a good sense of what those are, and I can say with a great deal of assurance that we are not having any cases that are associated with local transmission.”
Christ said other diseases carried by the Aedes ageypti mosquito, such as dengue and chikungunya, are already on the state’s radar, which meant that when Zika became a public health concern, the infrastructure was somewhat in place to track the mosquito.
“Those have been locally transmitted in Mexico for quite a while, and so we for the past three or four years have been doing surveillance of these mosquitoes and those diseases because we don’t want those locally acquired in Arizona either,” Christ said. “So we’ve expanded that plan to include Zika, and we’ve really stepped up the effort to prevent local transmission of all three diseases.”
While there are mosquitoes in Sonora that carry all three diseases, Christ said it’s unlikely those mosquitoes will appear in Arizona.
“Luckily, these mosquitoes don’t fly very far,” she said.
So far, there have not been any reported cases of locally acquired dengue or chikungunya in Arizona.
However, Zika could find its way into Arizona through a less direct method, just as it did in Florida, Christ said.
“Returning travelers who probably didn’t even know that they were infected because the symptoms were so mild, and they came back, got bitten by Florida mosquitoes and those Florida mosquitoes went and bit other people,” Christ said. “It’s hard to contain those mosquitoes.”
If someone is bitten by a Zika-infected mosquito, it would take two to seven days before he or she would begin showing the symptoms of a rash, fever, joint pain and conjunctivitis, if he or she shows any symptoms at all. Only one out of five people infected shows any symptoms, which typically last up to a week.
That’s why it’s important to continue using mosquito repellent and to wear long sleeves and long pants after returning from travel in a Zika-impacted area for at least two weeks to prevent the potential spread of the disease, Christ said.
“I don’t think that a lot of people who travel know how important it is to make sure that you are taking precautions from being bitten by mosquitoes when you get back,” Christ said. “We really encourage people to ensure that when you return from a place that does have Zika circulating that you take all of the precautions to avoid being bitten by a mosquito back here in Arizona and potentially infecting the mosquitoes.”
Garcia said the population most at-risk in the state are pregnant women, and they should avoid traveling to areas with local transmission like Sonora.
Pregnant women who become infected by Zika are at risk of passing the disease onto their fetus, which could cause birth defects like microcephaly, a condition in which a baby is born with a smaller head and brain as compared to other newborns.
For this reason, Garcia stressed the importance for a pregnant woman to be cautious with who they come into contact with .
“If someone’s sexual partner travels to Mexico, and they come back and they are sick, they could potentially make that pregnant woman ill and her baby ill by having sex with her,” Garcia said. “So if you’re pregnant or if you’re the sexual partner of a pregnant woman, you should avoid travel to those areas or you should make sure that you’re using condoms correctly and accurately with every act of intercourse.”
Christ said Arizonans can be proactive in preventing the spread of the disease by stopping it before mosquitoes ever even become infected with the virus.
“One thing that people can do is to make sure they take precautions around their home to prevent mosquito breeding,” Christ said. “Dump standing water, make sure you don’t have any mosquito breeding sites. Backyards have a lot of places where this specific mosquito can breed because they require just a very small amount of water.”
Christ said the most immediate public health problem currently facing the state isn’t Zika. It’s influenza.
