Boston officials are stepping up efforts to spot Ebola cases after the Hub area was hit by its first scare yesterday, when a man who recently visited Liberia was quarantined after walking into a Braintree medical clinic complaining of head and muscle aches.

That case comes as a Dallas nurse who wore a protective suit while treating the Ebola patient who died last week has also contracted the deadly disease — in what a local ER chief called “a game-changer” because it’s the first time someone has caught Ebola in the U.S.

“It gives us a heightened level of concern that even when we think that when we’re compliant with infection control precautions, infection can happen,” said Dr. Michael VanRooyen, vice chair of the Department of Emergency Medicine at Brigham and Women’s Hospital. “The scary part is that they don’t know where the breach was.”

Boston police Superintendent-in-Chief William Gross told the Herald last night he will be convening Ebola preparedness meetings with the heads of police, emergency management, EMS and fire, to get first responders on the same page about Ebola safety protocols.

“We’re going to be the first ones responding to these situations, so whoever gets there first should know the symptoms of Ebola and what to do next,” Gross said. “We don’t want anything like Dallas to happen here in Boston, where someone is turned away or sent home.”

Earlier in the day, Mayor Martin J. Walsh expressed confidence in local preparedness, but said a local Ebola case “seems like it potentially is inevitable.” And City Councilor Stephen J. Murphy, the council’s public safety chairman, called for tighter screenings at Logan International Airport.

“They should screen them better upon entry,” Murphy said. “I think that’s better safe than sorry.”

Local health officials said a man arrived at Harvard Vanguard’s Braintree office about 1:30 p.m., prompting the building to be temporarily shut down and workers and other patients to be held on site until the patient was taken in a hazmat suit to Beth Israel Deaconess Medical Center.

The hospital issued a statement late last night, saying, “After our initial evaluation, this patient does not appear to meet CDC criteria to be considered someone at high risk for Ebola and the likelihood of Ebola Virus Disease is extremely low. The patient will remain in isolation as we continue to evaluate and monitor the patient’s condition.”

Indeed, infectious disease experts warn against jumping to conclusions about Ebola. The same symptoms and West African travel history could just as easily indicate malaria or typhoid, Dr. Amesh A. Adalja, University of Pittsburgh specialist, told the Herald last week.

Harvard Vanguard spokeswoman Michal Regunberg said after the patient revealed to staff he’d been to Liberia, he was “directed by reception to go wait in his car” and “staff let him know that the ambulance was coming.” A few hours after he was whisked away with a police escort, his car — with several bright orange “biohazard” stickers attached — was towed.

Anne Roach, spokeswoman for the state Department of Public Health, said the steps were taken “out of an abundance of caution” and that the response was “consistent with public health protocols and safeguards.”

“There are no confirmed cases of Ebola in Massachusetts,” Roach said. “DPH has worked with area hospitals over the past several months on suspected cases of Ebola and they have all been quickly ruled out.”

Denise DiMarzio, who was in a Harvard Vanguard waiting room when the quarantine was ordered, described a harrowing scene, including “people running by with yellow precaution gowns on in masks and gloves.”

“They couldn’t tell me whether or not I should stay or leave, and that panicked me,” said DiMarzio, a nurse who is seven months pregnant. “I don’t know if he was coughing and had secretions on his hands and was in the same waiting room as I was. Makes me a bit nervous. No one’s really told us what to do. They just said take a shower and check your temperature for the next 21 days.”