As King County looks to slowly reopen its economy after months of closures, a comprehensive system of testing, contact tracing and quarantines will be needed to avoid a burst of new infections of the novel coronavirus, according to a new study from the Institute for Disease Modeling.

Such measures could enable economic and social activity in the region to double from current levels, without a corresponding increase in infections, the Bellevue-based Institute said in a report released Monday.

But if King County can’t increase testing capacity, fails in its efforts to notify the close contacts of positive cases or can’t persuade people to isolate if they have been exposed to the virus, new infections could skyrocket, the report says.

“It took a communitywide effort to get us into the relatively good situation we are in today with respect to limiting transmission,” said Dr. Jeff Duchin, health officer for Public Health – Seattle & King County. “And it’s going to take a robust, ongoing communitywide effort to allow us to move forward safely.”

King County remains in phase one of Gov. Jay Inslee’s four-phase plan to reopen Washington’s economy. The soonest King County could conceivably move to the next phase is Monday, but it is currently nowhere near the low levels of new cases that is among the criteria for reopening.

Duchin said the county is moving in the “right direction,” but “in the last couple of weeks there’s a lot more action happening and I’m concerned that may translate into disease transmission.”

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The state Department of Labor and Industries announced Tuesday that businesses operating in violation of Inslee’s stay-home order can be cited and fined for unsafe workplace conditions under new, emergency rules.

The state Department of Health and National Guard have ramped up their abilities to help county health departments with the tedious task of contact tracing — calling each person who tests positive for the virus and then calling all the people they have been in contact with and asking them to quarantine.

The state has trained more than 2,100 people for the task. Contact tracing is a fundamental and decades-old public health tool, but Public Health – Seattle & King County had to stop investigating each case of the virus in early March, as the number of cases became overwhelming.

The state is conducting about half of the contact tracing investigations in King County, Duchin said, but he’s hopeful the county will be able to handle all new cases by the end of June.

“Any plans we develop for contact tracing and case investigation must be sustainable so it can be maintained for the next two years,” said Sharon Bogan, a spokeswoman for Public Health – Seattle & King County.

State health officials confirmed 116 new COVID-19 cases in Washington on Tuesday, as well as eight additional deaths. Those numbers bring the state’s totals to 20,181 cases, 1,078 deaths and 3,338 hospitalizations.

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Locally, the virus’s reproduction rate has dropped from nearly three to slightly below one, according to most estimates. That means each person who contracts the virus is, instead of infecting three other people, infecting an average of fewer than one other person, resulting in the epidemic’s slow decline.

But if the county were to ease social distancing measures immediately without increased testing and contact tracing, the virus will come back faster than ever, the report, which is based on King County’s specific population and demographics, found.

“Without mitigation, we see a rapid return to exponential growth in infections, and the number of daily infections exceeds the previous peak by mid-June,” it says.

The report estimates King County had, by the end of April, cut the virus’s chances of transmission to 33% of what it would have been without social distancing measures. But nearly every cut in transmission opportunities also represents a lost social or economic interaction — a canceled trip to work or restaurant meal or movie ticket.

The report estimates social and economic activity could more than double, to about 75% of normal levels, with no big increases in infections, but only with significant countermeasures.

“This is good news, but it does speak to we can only really get there if we have the packages of tracing and testing and so forth,” said Daniel Klein, one of the report’s authors. “We have increased levels of countermeasures that we can apply.”

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Testing levels in King County would have to double, from about 2,000 tests a day at present to about 4,000. Quarantines for people with the virus, and their entire households, would have to begin on the day the person is diagnosed. And at least 70% of an infected person’s workplace contacts would have to be notified and begin quarantining within two days.

Duchin said he thinks the county has the capacity to increase its testing levels, but the contact tracing remains a challenge.

“We’re not there yet,” he said. “It’s definitely still a work in progress but it is in progress and it’s getting more robust.”

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