Doctors in Boston have expressed shock after 146 homeless people from a city shelter tested positive for Covid-19, despite none of the group showing any symptoms of the disease.

The 397 residents of The Pine Street Inn shelter were all tested last week after a cluster of cases were initially found, with over one third testing positive. The news has prompted renewed questions about how widespread the disease might be in society however,  given the lack of symptoms displayed by carriers at the home.

The Centers for Disease Control and Prevention is said to be “actively looking into the results” from the shelter according to Boston 25 News, with increased testing set to take place at other homeless shelters around Boston.

Dr. Jim O’Connell, president of the Boston Health Care for the Homeless Program, said the news from The Pine Street Inn “was like a double knockout punch”, not just because of the number of cases, but also the apparent lack of symptoms.

Executive director of The Pine Street Inn Lyndia Downie suggested that universal testing might be the only way to establish if the general population has similar levels of asymptomatic carriers.

“I think there are so many asymptomatic people right now. We just don’t know. We don’t have enough data on universal testing to understand how many asymptomatic people are contagious”, she said.

The “tip-of-the-iceberg” theory that millions of people have already unknowingly had Covid-19 came to prominence after the publication of an Oxford University study claiming half of the UK’s 66 million population had already contracted and recovered from the virus.

Although the study was criticised widely, the move towards increased testing of asymptomatic people in many western countries will shed further light on how accurate or otherwise the authors’ conclusions are.