By Louisa Moller

WORCESTER (CBS) – Asymptomatic coronavirus patients may have started the virus’s rampage on nursing homes.

Mounting data suggests staff and residents who were positive for COVID-19, but displayed no symptoms, allowed the virus to tear through nursing homes across the country.

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In a survey published in the New England Journal of Medicine, researchers tested residents at an anonymous nursing home for COVID-19 and found that more than half with positive results were asymptomatic at the time of testing and “most likely contributed to transmission.”

Dr. Eric Dickson, CEO controlling the coronavirus pandemic. (WBZ-TV)

An antibody test of staff at the Beaumont Nursing Home in Worcester, which was converted to a facility for recovering COVID-19 patients, found that 20 percent of staff likely had a mild case of the virus and developed an immune response to it.

“There was a reasonable prevalence of it in the community and such that it could be spread to patients,” said Dr. Eric Dickson, CEO of UMass Memorial Health Care, which conducted the testing.

“We think 50 percent of the population that gets coronavirus are asymptomatic or get mild symptoms,” Dickson said of the virus.

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In Ashland, the Board of Health voted unanimously to require all nursing and extended stay facilities to test their staff for coronavirus.

“A lot of times, these workers are not getting tested because they have no other means of income,” Town Manager Michael Herbert said during the board’s zoom meeting.

On Wednesday, the Residence at Valley Farm in Ashland began testing all of its staff and residents.

Dickson believes a combination of antibody and other testing is vital to stopping the coronavirus.

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“Testing when we see outbreaks for the actual virus and infection and antibody testing combined are going to be really powerful tools in understanding how we can control this awful virus,” he said.

Louisa Moller