(CNN) When an outbreak of coronavirus in a Boston homeless shelter prompted officials to do more testing, the results caught them off guard. Of the 146 people who tested positive, all of them were considered asymptomatic.

"These are larger numbers than we ever anticipated," said Dr. Jim O'Connell, president of the Boston Health Care for the Homeless Program. "Asymptomatic spread is something we've underestimated overall, and it's going to make a big difference."

O'Connell said Thursday that across the country medical professionals have just been looking for signs and symptoms in homeless people. While Boston aggressively tested residents at a second shelter after the asymptomatic findings, the city is considering what to do next, he said.

"All these things we are recommending for social distancing, you can't do that when you walk into a shelter," O'Connell said. "I think it is a real failure on our part, and we need to fix it quickly."

Washington, D.C., for one, has taken notice.

A spokeswoman for the Department of Human Services said Friday that Washington is aware of the asymptomatic cases in Boston and is modifying its testing procedure. She said the department will have details early next week.

'This caught us unprepared'

O'Connell's program, which provides medical care across Boston's homeless shelters, had put in place a rigorous screening system about three weeks ago. Every person who entered a shelter was tested for a fever and was asked if they had any other symptoms associated with Covid-19.

Then, two weeks ago, the Boston Healthcare for the Homeless Program noticed a small group of people had tested positive for the coronavirus at a shelter in the city's South End. To be safe, they coordinated with the state government to do universal testing of the shelter population over two nights. Out of the nearly 400 guests tested, 146 tested positive for Covid-19, according to O'Connell.

"This caught us unprepared, but the even more surprising finding is we screened all of them, and none had a fever, and very few had other symptoms," O'Connell said.

There was also a small cluster that was found at another shelter, which houses 450 men, and testing was done there Thursday night, O'Connell said. They were able to get more rapid tests from the state to do tests quickly, but officials are unsure if they will find the same situation at that shelter.

O'Connell said that the local and state government is collaborating with the CDC about how to proceed. He said the collaboration between different partners is necessary because the "problem is with the dimension of this virus" -- and he noted that even with all of this help, they might not be able to tackle the problem.

In a statement to CNN, the Centers for Disease Control & Prevention confirmed that it was consulting on the outbreak, but said the local state health department is in charge. The CDC did not address the fact that all who tested positive were asymptomatic.

New York focuses on temperature checks

O'Connell said in the shelter system in Boston there are about 2,000 single adults that are in the larger shelters on a regular basis. As of Thursday, about 1,000 people have been tested so far, and 250 people have tested positive.

In New York City, which has somewhere between 55,000 and 60,000 people in shelters every night, there were 537 Covid-19 cases, including 33 total deaths as of Thursday, according to the city's Department of Social Services. The department says its current screening policy includes questioning about symptoms and self-reporting any illness.

Citing "testing challenges," New York remains focused on "a mitigation strategy," prioritizing care for the most urgently ill. Those who have mild symptoms, including the homeless, are urged to avoid seeking tests, city health officials said.

The city is "aiming to implement temperature checks" with the homeless population, an official said.

Kiana Davis, a policy analyst at the Urban Justice Center's Safety Net Project, says that while the New York is making an effort to do temperature checks, it is not happening consistently at every shelter.

"Some shelter spaces have thermometers to check people's temperature, many don't," Davis told CNN.

The city's Department of Social Services also noted that it is working to move people out of larger congregate shelter settings so that it's possible to practice better social distancing. Davis noted that while the city has opened up 6,000 hotel rooms to help the homeless population be able to socially distance, people are often still sharing rooms and potentially spreading the virus.

In Washington, 88 people have tested positive and five people have died as of Thursday, according to the city's Covid information page. The total homeless population was a little over 6,500 as of January 2019, according to the United States Interagency Council on Homelessness. Washington's screening process, like Boston, requires a temperature check and self-reporting any other symptoms.

Moving forward in Boston

Since the beginning of the outbreak, Boston Healthcare for the Homeless has followed CDC guidelines on who can receive a test -- those who show symptoms and have a fever. Officials are still testing people who are symptomatic at all shelters, but they are now concerned that there is no way to effectively stop the spread without testing everyone.

In the meantime, the program has made a concerted effort to distance people who've tested negative as much as possible. Everyone who tested negative at the first shelter was taken to the Suffolk University dorms so they wouldn't have further exposure.

O'Connell emphasized that all of these guidelines to isolate and protect yourself from the virus are essentially useless when you are homeless, and that is the responsibility of the others to protect such vulnerable people.

Last week Boston Mayor Marty Walsh and Massachusetts Gov. Charlie Baker announced that the Boston convention center would offer 500 beds for the homeless as part of the temporary healthcare facility being set up in that location. O'Connell said there were 60 people there as of Thursday.