Maricopa County officials announced Thursday plans to ramp up COVID-19 contact tracing by up to 10 times the current capacity, as county cases are expected to rise.

Contact tracing is the process by which public health investigators interview an individual who tested positive to find out everyone they interacted with and who may be at risk of contracting the disease. It's an essential step in the public health response to try to limit the spread of an infectious virus.

Twenty-five infectious disease investigators, five of whom are dedicated solely to long-term care facilities, work to interview every positive case in Maricopa County. Positive cases were at 2,970 for the county as of Thursday, per state numbers.

Eight to 10 times more people will be added to that team in the weeks ahead as positive cases continue to rise, especially with more testing and a possible reopening of the state. The timeline and details are still in the works, said Dr. Rebecca Sunenshine, Maricopa County's medical director of public health.

How does contact tracing work?

Contact tracing has been a fundamental public health practice for more than a century, Sunenshine said. It's been used for almost every reportable person-to-person infectious disease in Arizona and it's proven useful for interrupting the spread of infections.

Once the county learns from state records of a positive COVID-19 case in Maricopa County, an investigator immediately begins a case investigation.

"Investigators are part public health, part detective and part social worker trying to establish rapport with this person that they've never met, and trust, and at the same time trying to cover as much information as possible without judgment," Sunenshine said.

They do an extensive interview with the individual who tested positive, asking about household members, health care workers they interacted with and any other contacts in the community. Investigators find out whether health care workers had any lack of personal protective equipment and who else was in the facility at the time.

They ask about every person the individual spent time with while infected — meaning anyone they interacted with within 6 feet for more than 10 minutes, starting two days before they first showed symptoms, Sunenshine said.

Interviews can take between one and three hours depending on how long the individual was sick before getting tested, how many people they had contact with and language barriers, Sunenshine said.

After asking about every day and every activity, investigators have a list of individuals who may have been exposed. When county resources permit, each one of them is contacted by public health officials and told they were recently exposed to COVID-19. Investigators provide information on symptoms to look for and what to do if people get sick. They never share the interviewee's name to ensure confidentiality.

County public health officials may continue to check in with the individual on a daily basis, depending on the severity of their case and may monitor close contacts as well. Quarantined individuals are typically contacted daily to make sure they have enough food and health care, Sunenshine said.

Sunenshine said the team interviews up to 150 individual people each day. All conversations are confidential because of health privacy laws.

Maricopa County's contact tracing

When case numbers were relatively low in the early weeks of COVID-19, investigators carried out the full "traditional public health contact tracing" process, with investigators talking to each and every contact. But as case numbers began to rapidly increase, the county modified its process to "mediated contact tracing," Sunenshine said.

This means each positive case is still interviewed, but public health officials ask the individuals themselves to reach out to all of their contacts and provide information on potential exposure. Investigators give them written instructions.

The department doubled its pre-COVID-19 staff to 25 to handle the large number of positive cases to interview. But that's still not enough and they have had to revert to having individuals talk to contacts rather than county public health investigators doing so.

The county now plans to scale back up contact tracing capacity by eight to 10 times so it can return to "traditional contact tracing investigations" as testing becomes more widely available and case numbers continue to rise, Sunenshine said.

Sunenshine said she can't yet say the timing of the scale-up. The county is working with partners on how to train and increase the workforce. Some of the funding is available through the county's CARES Act allocation, she said.

Sunenshine expects an increased need for contact tracing once testing expands, as more available testing means more identified cases. The Arizona Department of Health Services announced Thursday it will expand testing availability to anyone who thinks they could be infected.

“As the testing increases, we need to be able to enhance our investigators and the number of people that we have doing the contact investigations to keep up with the testing," Sunenshine said.

And as the state considers when to gradually reopen, more social activity is likely to spark more positive cases. So the need for contact tracing will only increase.

"Right now, what we want to do to have more complete surveillance of the disease in our community is we staff up, we put this plan in place and we will have more people so we go back to directly contacting every person who is a potential contact," county spokesman Fields Moseley said. "So more thorough contact tracing."

Reach the reporter at Alison.Steinbach@arizonarepublic.com or at 602-444-4282. Follow her on Twitter @alisteinbach.

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