The staff at Cayman’s Mosquito Research and Control Unit has been putting in long days as they fight to stop Zika transmission in Grand Cayman.

MRCU Director Bill Petrie said Tuesday that his staff have been working through evenings and weekends to kill the Aedes aegypti mosquitoes responsible for carrying the virus, and creating chemical barriers to keep the mosquitoes away from preschools and homes of pregnant women.

Read more about Zika in Cayman

Zika, which has swept across the Americas from Argentina to Florida, was found in Cayman in July. As of Sept. 6, Cayman has confirmed five cases contracted locally and another six from overseas, according to the Public Health Department. All of the local cases involve people living in George Town.

Dr. Samuel Williams-Rodriguez, Cayman’s leading public health official, said 80 percent of infected people do not show symptoms. “The number of people [infected] is expected to be much higher,” he said.

For people who do experience symptoms, they tend to be mild with a rash, fever and conjunctivitis, or pink eye. The major concern of the virus is for pregnant women, as Zika is linked to severe birth defects in babies born to infected mothers. Babies born with tiny heads and underdeveloped brains, a condition called microcephaly, have characterized the virus spread through South and Central America and the Caribbean.

Zika testing through the HSA has been available only to people who show symptoms of the virus and have not traveled to other Zika countries. Only pregnant women who show symptoms are given the free test. Dr. Williams-Rodriguez announced Tuesday that the Health Services Authority will offer Zika testing for $100 to anyone who wants to be tested.

Zika is also known to be transmitted sexually.

In an effort to protect pregnant women and growing families, Cayman’s MRCU is treating every preschool on Grand Cayman. Its staff are also inspecting and treating the homes of pregnant women who request the free service. (The mosquitoes that carry the Zika virus are not found on the Sister Islands.)

The MRCU director called the strategy “barrier treatments” where the unit sprays a liquid insecticide to coat walls and plants and create an area essentially surrounded by insect repellent to keep out the mosquitoes.

“It’s designed to create a perimeter,” he said. Crews treating schools and the homes of pregnant women will also inspect the property to make sure there is no standing fresh water caught in rain gutters, old tires, potted plant dishes, and anywhere else Aedes aegypti like to breed.

Mr. Petrie said 77 pregnant women over the last week had requested the inspections and home treatments. As of Tuesday, he said, 61 of the homes had been inspected and treated.

“This is the first time we’re separating out a set of requests,” Mr. Petrie said, noting the serious health concerns for pregnant women.

He said the MRCU is using everything it can to stop the mosquitoes from spreading the disease. From new research with genetically modified mosquitoes, to the MRCU airplane daily dropping insecticides around the island and crews fogging areas with trucks and by hand, Mr. Petrie said they are using all the tools at their disposal to stop the Zika outbreak from worsening.

“Everybody is working flat out,” he said, with MRCU staff even working over the weekend to treat preschools while the children are not there. He said his staff is dealing with the outbreak as they did with the chikungunya and dengue viruses.