MIAMI—The parents of a 12-year-old Zachary Reyna are praying for a miracle.

Each day for the past few days, they have gathered at Miami Children’s Hospital, hoping that Zachary can overcome a rare “brain-eating” infection in his brain. Called Naegleria fowleri, the microscopic single-celled living amoeba is commonly found in freshwater lakes, ponds and rivers and is usually fatal, once it infects humans.

On Wednesday, Zachary’s uncle Daniel Reyna said the family is focusing on Zachary and publicizing a Facebook page and hashtag made in his honor “pray4number4.” He said they will be willing to talk more aboutZachary once his condition improves.

Zachary was infected while knee boarding with friends on Aug. 3 in a water-filled ditch near his family’s LaBelle home in southwest Florida, family members say. State health officials said it is a medical mystery why some people who swim in amoeba-containing water get the fatal nervous system condition while many others don’t.

The parasite generally enters the body through the nose and travels up to the brain. Once inside, the amoeba can cause a brain infection called primary amebic meningoencephalitis, or PAM, and destroy brain tissue, the Florida Department of Health said earlier this week.

“The effects of PAM on the individuals who contract the amoeba are tragic,’’ said Carina Blackmore, Florida’s interim state epidemiologist in a statement.

“The low number of infections makes it difficult to know why a few people have been infected compared to the millions of other people that used the same or similar waters across the U.S.,” Florida officials said in a news release.

Initial symptoms usually start within 1 to 7 days and may include headache, fever, nausea and vomiting. The disease progresses rapidly, and other symptoms can include stiff neck, confusion, loss of balance, seizures and hallucinations.

State officials said people can reduce the risks of becoming infected by limiting the amount of water going up the nose, avoiding water-related activities in warm freshwater when temperatures are high and water levels are low, and avoid digging in or stirring up sediment while in shallow, warm freshwater areas.

The Centers for Disease Control and Prevention in Atlanta says victims die on average about five days after infection. Some victims are diagnosed after they die.

On Wednesday morning, five LaBelle area pastors and hundreds of residents gathered at the LaBelle Veteran’s Memorial Park for a prayer vigil.

It was organized by Susan Whidden, a resident who works at Seacoast National Bank and donations were taken on behalf of the family, said Brenda Barnes, spokesperson for the Glades County Department of Health.

In a YouTube video, posted by user “Don Browne,” the organizers and leaders spoke, occasionally choking up, and noting that they did not know Zachary or his family, but wanted to show support because it “could have been them.”

A post on the Facebook page for Zachary includes additional information on how to donate to the family to help cover the youngster’s medical expenses and to raise awareness. The latest post is a picture of Zacharyhaving fun atop a bright-orange all-terrain vehicle.

The family’s last post on the page, which has more than 4,000 “likes,” came shortly after the vigil began on Wednesday morning and offered thanks to the community:

“We want to thank everyone who came out this morning to pray. We watched via FaceTime and were able to pray and sing with you. It means so much to us that our community has gone out of their way to pray and support us. We love you all.”

“When something happens close to home we really come together,” said Barnes of LaBelle. “That’s why I love living in a small town.”