When a person tests positive for COVID-19, the public health department’s team of epidemiologists spring into action.
The investigation begins with an extremely low-tech tool: a conversation.
“We interview the person who’s sick, [and] we identify all the people they’ve been in contact with in the period when they might have been infectious,” state epidemiologist Dr. Matthew Cartter said.
And while self-quarantine and social distancing are among the most effective ways to prevent the spread of COVID-19, for those tools to work, officials have to identify the people who are most likely to have come in contact with the virus.
When a patient does test positive for the disease, it triggers a public health response known as “contact tracing,” where officials backtrack the patient’s movement over the previous two weeks in search of anyone else who might have contracted the disease, even if they’re not showing symptoms.
Contact tracing is a critical tool allowing public health officials to connect with those who may be infected and encourage the appropriate steps. Once the virus begins to spread more rapidly, however, that becomes a far more difficult exercise.
Although COVID-19 has brought contact tracing into the spotlight, Cartter said it’s something his staff does regularly for other transmissible diseases, such as measles.
The state Department of Public Health has about 20 epidemiologists who are trained in contact tracing, Cartter said.
These epidemiologists “do this every day for other diseases as well,” Cartter said. As part of the process, it’s crucial for officials to figure out how the a patient comes in contact with the virus in the first place, he said.
As of Sunday evening, there were 26 confirmed cases of Connecticut residents testing positive for COVID-19, the disease caused by the coronavirus.
Hartford health investigators spent the weekend chasing what might be one of the most significant cases thus far: A Hartford man who tested positive for COVID-19 and who had attended a funeral service where as many as 400 people were present.
“We can assume there were many many contacts within the community,” Hartford Mayor Luke Bronin said Sunday during a press conference at UConn Health in Farmington.
Tracing the spread of the virus
For COVID-19 specifically, the focus is on the patient’s family and coworkers, Cartter said. That’s because the 2019 coronavirus spreads mainly through close and prolonged contact.
Although the home and the workplace are the investigators’ highest concerns, Cartter said any situation with close contact could lead to viral spread — for instance, dinner parties or dates. If investigators find a patient has also been in those situations, they may expand the investigation.
“We’re really talking about being within four to six feet of somebody for a period of time,” Cartter said. “We’re talking close contact, not somebody you passed in the hall.”
Cartter added the virus is most likely to spread from the initial patient’s coughs and sneezes.
“To be a really effective transmitter, you need to be coughing or sneezing,” Cartter said.
Once the investigators identify possible contacts, they reach out to those people and ask them to self-quarantine for 14 days. That means staying at home and distancing themselves from other family members.
The public health department regularly checks in with those people, Cartter said, and if any of them become ill, the department will arrange to have them tested for COVID-19.
Cartter said that if any of the first patient’s contacts becomes ill or tests positive for COVID-19, that could trigger a second layer of contact tracing, backtracking the second patient’s movements.
But initially, “the focus is on making sure that the first level of contacts are all staying home and being monitored,” Cartter said. “If somebody develops symptoms, that triggers wider” investigations.
Colleges and hospitals
Although the state public health department leads the charge on contact tracing, the staff works in conjunction with local hospitals and other entities, such as universities, Cartter said.
Typically, Cartter said, the public health department handles contact tracing out in the world, while hospitals and universities handle the task within their own walls.
So far there have not been any confirmed COVID-19 cases on Connecticut college campuses. However, Cartter said that places such as UConn and Yale University have the capacity to conduct their own contact tracing, with the public health department standing by to give any needed advice or assistance.
While the universities still have time to prepare — and many are shutting down their campuses to avoid cases in the first place — for some hospitals, the virus is already a reality.
Hospital workers affiliated with Danbury and Norwalk hospitals have been diagnosed with COVID-19, and Bridgeport, Danbury and Norwalk hospitals were the first in the state to treat additional patients who are not health care workers.
In all of those cases, Cartter said, the hospitals work to determine any additional patients and health care workers that may have come in contact with the diagnosed person. The hospitals do their own contact tracing “because they know their people best,” he said.
It’s a crucial job.
“Our first priority is to keep our hospitals open. That’s our first priority, hospital contacts,” Cartter said.
Dr. David Banach, an associate professor of medicine and an epidemiologist at UConn Health, said the hospital staff, much like the public health department staff, is accustomed to contact tracing.
In more typical times, Banach said, the hospital might trace the movements of a patient who’s been diagnosed with tuberculosis or chickenpox.
“There’s precedent for these kinds of things,” Banach said.
The hospital’s investigative work is mostly a matter of searching through paperwork, he said. Medical forms offer a record of each patient’s movements, from one patient room to the next or from a patient room into surgery.
After determining which patients and workers came into contact with the diagnosed patient, Banach said the hospital would also evaluate the type of contact. For example, some health care workers may have provided close-contact care, but could still be low-risk if they wore protective equipment during each interaction.
If the hospital identifies a concerning contact, Banach said, they’d reach out to that person with next steps, such as a 14-day self-quarantine.
Limitations
Earlier last week, when the number of COVID-19 cases in Connecticut was still in the single digits, Cartter said it was entirely feasible for the public health department’s epidemiologists to track down those patients’ recent contacts.
But the number of cases in the state has steadily grown. And eventually, Cartter expects the number will grow to a point where contact tracing is no longer feasible.
“This case investigation [and] contact identification will last until we have widespread community transmission,” Cartter said. “And then it’ll stop. There’ll be too many people.”
While other states are already in the throes of community transmission, the Connecticut case announced Wednesday, of an elderly New Canaan man, may mark the start of the phase in this state.
And even before Wednesday, Connecticut was already seeing a version of that reality. Cartter noted the first two Connecticut residents to test positive had most likely come in contact with the virus during domestic travel.
The first, a middle-aged Wilton resident, is believed to have come in contact with the 2019 coronavirus on a trip to California. And the second, a Bethlehem resident, is believed to have come in contact with the virus on a trip to Nevada.
“We’ve moved to a different place now,” Cartter said. “This is ongoing transmission in the United States.”
Emily Brindley can be reached at ebrindley@courant.com.
