But the tight quarters at shelters such as the Central Union Mission make Coleman and others there vulnerable to illnesses. Crowding and poor hygiene create an environment primed for the flu to spread, said Jeff Engel, executive director of the Council of State and Territorial Epidemiologists.
Subpar conditions among the homeless have led to other outbreaks in recent years. In Atlanta, a drug-resistant tuberculosis problem began in a homeless shelter in 2008 and infected more than 100 people in the city and surrounding county, according to the health department.
Last year, poor access to restrooms among the homeless community in San Diego and other parts of Southern California fueled a rash of hepatitis A cases that infected hundreds and killed 21 people, according to the state's health department.
"You've got very vulnerable people, who've got underlying health problems, poor access to health care, poor environmental conditions, crowded together," said Kushel. "And then, you throw in a particularly nasty flu and then you really got a recipe for disaster."
In Washington, flu activity is two levels below the most severe "widespread" category, according to the CDC. However, the number of people who have been infected so far is the highest in five years, with 2,150 confirmed cases as of Feb. 17. Maryland reported 23,111 laboratory-confirmed cases as of Feb. 17, and Virginia health officials said the state had 2,652 cases as of last Friday.
Deborah Chambers, senior director of strategic partnerships and community engagement at Central Union Mission, said the facility has been on alert this year for the flu. In addition to daily cleaning, hand sanitizers have been placed throughout the building and flu shots are offered, she said.
These efforts are also in part a response to a flu outbreak last year that "ran through the whole building," Chambers said. This year, other than a few staff members falling ill to the virus, she said, the organization has not seen a spike in the number of flu cases.
Nonetheless, the organization held another vaccine clinic Feb. 9.
Unity Health Care, a nonprofit health system in the district that caters to low-income residents, also held a flu clinic, on Jan. 25 at The Day Center and Adams Place shelters for the homeless. Although the health system promoted the vaccine in the fall, Dr. Catherine Crosland, medical director of homeless outreach services for Unity, said the events had marginal success.
She and Caroline Garber, a Walgreens pharmacist with a big, red bag full of 50 vaccine doses, arrived to try again. Paul Martin was their first client. "I really don't like needles, but I do need the flu shot," he told Garber.