Maryland health officials announced Thursday the state's first confirmed case of Zika, a mosquito-borne virus alarming public health officials with its rapid spread throughout Latin America and the Caribbean and suspected links to birth defects.
The unidentified Maryland resident recently returned from a Central American country and has recovered. Officials would not say where in the state the patient lived.
Cases have been found in neighboring jurisdictions, including Virginia, Delaware and Washington, and more cases are expected in Maryland as local health authorities ramp up testing and reporting. Doctors and officials from the state Department of Health and Mental Hygiene, however, sought to calm fears Thursday.
"This was an event that was expected to occur as travelers returned to Maryland," Howard Haft, deputy secretary for public health, said during a news conference announcing the case. "This is not a significant health risk to Marylanders in general."
The World Health Organization declared Zika a public health emergency on Feb. 1 after the virus began spreading widely and was suspected of causing a devastating brain disorder known as microcephaly, in which brain development is incomplete, in babies born to infected women.
Brazil, where there have been thousands of cases of Zika, is at the center of the epidemic, but at least 33 countries have reported the virus. That led the U.S. Centers for Disease Control and Prevention to issue a travel warning for about 20 countries and begin collecting blood from potentially infected travelers for testing.
Maryland has sent 17 samples to the CDC. One case was positive and two tested negative, while the rest have not been returned, Haft said. The state agency plans to begin testing for the virus in its own lab within the week and to be reporting case counts weekly.
Nationally, the CDC reports there have been 52 confirmed cases as of Feb. 10.
Officials have said they expect more cases along the nation's southern border where the Aedes mosquitoes that carry the virus are more common. Mosquitoes of any kind are uncommon in winter in Maryland, so for now cases are expected to be entirely among travelers. But state health officials said they are communicating with the agriculture department about pest control.
Dr. David Blythe, the state epidemiologist, said that only one in five of those infected shows symptoms, which include red eyes, rash, joint aches and fever. It's rarely severe, but in addition to microcephaly, Zika has also been linked to Guillain-Barre syndrome, an immune system disorder that can cause paralysis.
He said those who have traveled to affected countries should talk to their health care providers.
That advice is especially important for women who are pregnant and have traveled to affected countries — or who have partners who have traveled to them — even if they have no symptoms, said Dr. Jeanne Sheffield, director of the division of maternal-fetal medicine at Johns Hopkins Medicine. There have been a small number of cases in which infected men have passed the virus to their partners through sex.
There is no treatment or vaccine, but symptoms can be managed with rest, fluids and acetaminophen, and fetuses can be monitored, said Sheffield, who was representing the American College of Obstetricians and Gynecologists.
She also advised pregnant women against traveling to affected countries. Those who must travel should avoid mosquito bites by wearing long sleeves and pants, using clothing treated with the organic insecticide pyrethrin, staying indoors in screened and air-conditioned rooms when possible, and applying insect repellent that contains DEET.
"The vast majority of cases right now is through mosquito bites, and right now in Maryland, mosquitoes aren't present," she said. "Those people who don't travel are not at much risk."
At the federal level, health officials are monitoring the spread of Zika and helping fund research into a vaccine. On Monday, President Barack Obama asked for $1.8 million in emergency funding from Congress for the domestic and international response.
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Sen. Barbara A. Mikulski, a Maryland Democrat who sits on the Senate Appropriations Committee, called the situation serious and said she'd be evaluating the funding request.
"I have three principles for the federal government's response to Zika," she said in a statement after a hearing in Washington on Zika. "First, the response must be driven by science and not panic. Second, Zika must be fought at its epicenter, which is the best way to limit its spread here. Finally, the development of a vaccine and treatments must be a top priority."
It could be years before a vaccine is developed, said Dr. Matt Laurens, a pediatric infectious disease specialist and associate professor at the University of Maryland School of Medicine.
He also doesn't expect a big outbreak in Maryland, though the state will likely see more cases, mostly from travelers.
"It is probably good to keep it in perspective and not freak out too much," Laurens said.
Baltimore Sun reporter Andrea K. McDaniels contributed to this article.