John Montanaro, a technician with Mosquito Joe, mixes a mosquito barrier for a residential property in Rockville, Md., on May 10. (Bonnie Jo Mount/Washington Post)

Like a lot of pregnant women, Christine Kaineg carries a bag of supplies to get her through the day: Kind granola bars for hunger, a big bottle of Tums and a new staple — mosquito repellent.

At almost eight months pregnant, the mom-to-be has read about the babies being born with severe brain abnormalities in Brazil and other countries, where birth defects have been linked to the mosquito-borne Zika virus.

With mosquito season underway in the Washington region, Kaineg isn’t taking any chances.

“I know it’s not in the area,” said Kaineg, who lives in Alexandria, Va., and works for a federal contractor. “But I also don’t want to be Patient A at such a critical time in my life.”

Apparently a lot of Washington-area residents are taking precautions. Mosquito-control companies across the region say that business is booming.

JChase Bernetich, technician with Mosquito Joe, applies a mosquito barrier to a residential property in Rockville on May 10. (Bonnie Jo Mount/Washington Post)

Al Tardiff, operations manager for Capitol Mosquito Control on Capitol Hill, said that calls to his office this spring have doubled from last year. The company recently bought a fifth vehicle and hired another full-time technician.

“They tell me they’re pregnant or they plan on getting pregnant so they want to know how effective our products are,” Tardiff said.

Kevin Wilson, chief executive of Mosquito Joe, said the company’s locations in the South, where mosquito season started this winter, have reported more than a 50 percent jump in new customers compared with last spring. Mosquito Joe franchises in the Washington area have seen a 32 percent increase.

“The real sign will be in June and July, when the kids are out of school and start getting bit,” Wilson said. “That’s when we’ll see the uptick in volume. I can’t image it this year, when the kids are getting bit, and all people are thinking about now is Zika.”

Public health officials say that there is a good reason for concern. The Asian tiger mosquito, the most common species in the region, has been found to carry Zika in other countries. Moreover, experts say, local mosquitoes are revving up just as summer vacations are set to begin, and the Washington area typically sees robust travel to the Caribbean and Latin America — all places with locally transmitted Zika.

Although there have been no confirmed cases of mosquito-transmitted Zika in the continental United States, officials say, the start of the mosquito season this month has significantly increased the chances in the Washington area. Also, the record-breaking string of rainy days has left behind soggy yards — prime environments for mosquitoes to lay hundreds of eggs.

With days of rain drenching the D.C. area, fears of zika-carrying mosquitoes are growing among many. The director of the National Institute of Allergy and Infectious Diseases, Dr. Anthony Fauci, says it's only a matter of time before the U.S. experiences outbreaks. (WUSA9)

Local health officials say they do not want to spread alarm, but they are urging pregnant women and everyone else to help prevent Zika by ridding their yards of standing water and wearing mosquito repellent daily.

“We don’t know if it will ever come to our local mosquito population, but we do know if it does come, bad things can happen — so we want to prepare for the worst,” said David Goodfriend, director of the Loudoun County Health Department. “If all that comes out of it is fewer people get bitten, that’s a good thing. And if it does come here, [prevention efforts] will be critical.”

As of May 11, the continental United States had 503 confirmed Zika cases, including four in the District, 16 in Maryland and 15 in Virginia, according to the Centers for Disease Control and Prevention. All have been people who traveled to Zika-affected countries.

Until this month, the Washington-area cases were not considered a public health threat because there were so few mosquitoes to spread the virus. Now that the Asian tiger mosquito has taken flight, concern is mounting, particularly for pregnant women.

Ulder Tillman, Montgomery County’s health officer, said that the Washington region has the “set-up for the likelihood of local transmission.”

“People shouldn’t panic, but they should follow our recommendations,” Tillman said. “Our only defense here is prevention.”

Tillman noted that there is no vaccine for Zika, and it can be transmitted sexually. Another complicating factor: About 80 percent of people with the virus do not feel sick, and those who get the most common symptoms — fever, rash, joint pain and conjunctivitis (pinkeye) — may not link them to Zika.

Rita Driggers, director of maternal fetal medicine at Sibley Memorial Hospital in Washington, said she sees women every day who have traveled to a Zika-affected country seeking ultrasounds to rule out abnormalities in their fetuses. She said many of her patients took “babymoons” — a last-hurrah big trip as a couple — in the fall, before many Americans were paying much attention to Zika.

“I have no doubt we’ll be seeing cases of locally transmitted Zika virus with this mosquito season,” said Driggers, who co-wrote a recent paper about Zika-related fetal brain abnormalities. “All it’s going to take is for one person with active Zika in their blood to get bitten by a mosquito, and that can start the spread.”

Driggers said she is particularly concerned “that there’s just a lot we don’t know about Zika,” including how accurate tests are for the virus in asymptomatic people and the risks to the fetus at different stages of development.

Based on how similar viruses have spread, health experts say, Hawaii, Texas and Florida are at the highest risk of experiencing Zika spread by local mosquitoes.

The key to how far or how quickly the virus could spreadin local mosquitoes would depend on the number of pests, experts say. Washington-area jurisdictions are urging residents to empty anything that holds water in their yards — flower pots, toys, folds in tarps — because the Asian tiger mosquito is known as a “container breeder” that lays its eggs close to its sources of blood in humans and their pets.

In addition, the Maryland Department of Agriculture has hired eight new staffers to scout out mosquito breeding grounds around the state. In Northern Virginia, some moviegoers will soon see a mosquito-prevention video amid the previews. In Montgomery County, obstetricians are giving patients state-supplied Zika prevention kits that include educational materials and mosquito repellent. D.C. health officials are holding “Fight the Bite” open houses at recreation centers and handing out prevention kits with mosquito repellent and condoms.

“The concern really comes in that we don’t really know how this virus is going to exhibit itself in Maryland,” said Daniel Schamberger, acting program manager for the mosquito control section of the Maryland Department of Agriculture. “We know we have this [Asian tiger] mosquito population, but we’re not exactly sure how the virus would move within Maryland. We know we need to be very vigilant.”

The message — or at least the mounting concern — is getting through.

Some pregnant women say that they are taking precautions against Zika while trying not to become unduly anxious. Some have canceled trips down South and have stopped biking or walking to work to limit their time outdoors.

Kyra DeBlaker-Gebhard, who is eight months pregnant with her third child, said her doctor told her not to worry about Zika. But DeBlaker-Gebhard, an interior designer who lives on Capitol Hill, said that she is checking her window screens, wearing mosquito repellent and scouring her yard for standing water.

“I’m suddenly aware of any bug flying around the house, thinking, ‘Is that a mosquito?’ ” DeBlaker-Gebhard said. “It concerns me that people are coming back from traveling [to Zika-affected countries], and now mosquitoes are around. What if a mosquito bites them and then bites me? It seems plausible.”

Jackie Ross, five months pregnant, said she and her Capitol Hill neighbors plan to hire a mosquito control company to spray all of their yards. She said she also will wear long sleeves and pants all summer.

“Usually we have people over and hang out outside,” Ross said, “but I don’t think we’ll be doing that this summer.”