Maryland already has logged six cases of the virus among travelers this year, including one person in the Baltimore metro area, and Florida has reported residents infected locally.
With mosquito season about to begin, state and local public health officials are gearing up efforts for further spread of the Zika virus blamed for devastating brain defects in newborns and neurological and eye problems in adults.
The effort to prevent infections gained added urgency this month after researchers tied the mosquito-borne virus to potentially deadly heart problems.
As the weather warms up, public health and medical officials advise pregnant women and adults generally to stay vigilant against mosquito bites, which are blamed for transmitting the virus. The U.S. Centers for Disease Control and Prevention warned people about visiting 63 countries with active transmission, mostly in Central and South America.
"We're worried about an epidemic hitting here and we wanted to be prepared," said Dr. William May, co-director of the Johns Hopkins Zika Center, a multidisciplinary center that opened last year for infected patients to get care and researchers to investigate the virus in one place. "We've already seen patients and we've fielded a lot of calls."
May said there has been a slow parade of people infected with Zika from inside and outside Maryland and from outside of the country. Patients include three babies born to infected mothers whom they are monitoring for effects of Zika.
The care being provided to patients and research conducted at the center and elsewhere is informing how the center's specialists treat the next patients, he said.
For example, patients must now see a cardiologist since a Mayo Clinic study recently determined that Zika can cause dangerous heart rhythm problems and heart failure in infected adults.
May, who's also an ophthalmologist at Hopkins' Wilmer Eye Institute, already knew doctors needed to examine the eyes of all infected babies and adults for complications.
"We've discovered a lot of things about our patients," he said. "But one researcher I talked to said we may just be seeing the tip of iceberg."
Since doctors in Brazil began to suspect the virus was causing serious harm to fetuses in 2015, researchers have rushed to understand its path from infected mother to a fetus' brain, and its other effects. The World Health Organization declared a public health emergency last year and funding was dedicated to promoting preventions and finding treatments.
There currently are no specific therapies for pregnant women, who seem to be the most affected by infections. They face potential miscarriages or stillbirths or babies born with a severe defect called microcephaly, which stunts growth of babies' heads and brains. The babies may have other problems immediately or later, collectively called Zika syndrome.
Baltimore native Sara Mathes knows firsthand about what can happen to those infected with the virus. She was living in Puerto Rico, and as she was planning to return home last year she developed a head-to-toe rash, flu-like symptoms and red eyes. Five of her friends also got sick.
Mathes, now 38 and living in New Jersey, still had tingling in her arms and legs when she arrived in Baltimore and decided to go to the new Hopkins center. A blood test confirmed she had Zika.
People, especially pregnant women, should cover up, use mosquito repellent, check travel advisories and call their doctor for testing and monitoring if they think they've been exposed, she said.
There have been 5,139 cases of Zika nationally, including 1,534 pregnant women, according to the CDC. Most cases were travel related, though a few cases of local transmission were reported in Florida.
The Maryland Department of Health and Mental Hygiene continues to monitor for Zika and report cases, which so far this year have included four in the Maryland suburbs of Washington and one on the Eastern Shore. The latest case, the state's sixth, was reported in the Baltimore region last week. There were a total of 174 cases statewide in 2015 and 2016.
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State health officials still are formulating plans for this summer. The department handed out kits last year to pregnant women that included information, repellent, larvacide and condoms because the virus also can be sexually transmitted. It worked with state agriculture officials to expand mosquito control spraying.
In Baltimore, health department officials also handed out kits and worked to drain standing water. They are working on a similar plan for this year.