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The number of homeless individuals in New York City’s crammed shelter system infected with the coronavirus exploded to 30 from just a single case reported last week – with one being referred from the equally stressed public hospital network.

One of the homeless people who tested positive was sent to a shelter by a public hospital because the person exhibited only mild symptoms and was not deemed sick enough to be admitted, a Department of Homeless official said.

The hospital referral was first reported by The City.

Anticipating a massive increase of infected shelter residents, DHS has identified 500 isolated units in the system that can be used to quarantine its clients. These units will be located in facilities separate from the regular homeless population, said spokesman Isaac McGinn.

The 30 COVID-19 cases were identified across 22 shelter locations. The sprawling shelter system serves 58,000 homeless individuals at 450 sites.

Eight of the infected shelter residents were ill enough to be hospitalized, 10 are quarantined in separate locations, seven are “self-isolating” in their own units and five have left the shelter system, McGinn said.

The individual Health and Hospitals case referred to the shelter system did not have a known address, McGinn said.

“As testing increases exponentially and thousands more positive cases are identified statewide, we have identified additional positive cases amongst the New Yorkers experiencing homelessness who we serve. We continue to work closely with our essential not-for-profit provider partners to keep our clients informed and to connect anyone who needs it to medical care or to isolation for monitoring and recovery,” McGinn said.

“Following the lead of our City’s health experts, we are working together across agencies to adapt and respond to this evolving situation in support of our most vulnerable City residents.”

Health and Hospitals had no immediate comment.