With all the discussions around the pandemic and responsive measures such as handwashing, masks and lockdowns, there is one strategy that could prove crucial to public health efforts.
In October, a doctor with the World Health Organization called contact tracing the “game-changer” needed for fighting the coronavirus in the near future.
It’s a sentiment echoed by the north Island’s medical health officer, Dr. Charmaine Enns. In an interview with the Record, she emphasized what contact tracing is, how it works and why it is so important in stopping the spread of COVID-19.
“This is the most important public health intervention we have,” she said. “We have only so many tools in our toolbox.”
Enns wants to see people live their lives, but do so in a manner that will protect them. To keep communities from having to go into lockdown, public health professionals and the public need to be vigilant in their efforts to trace the potential spread whenever a COVID-19 case crops up.
Case ID, then contact follow-up
The process is two-fold, starting with case identification, then contact follow-up. The aim is not to test everyone, only those with symptoms that could be COVID-19. When someone tests positive, public health staff respond quickly, with the positive lab result sent directly to the communicable disease (CD) nurses and the medical health officer in the area of the ‘case’ – in other words, the person who tests positive.
People are considered infectious for 10 days from the first day of their symptoms, though some symptoms can linger and repeat swab tests can remain positive for up to 100 days. However, the person is no longer infectious and not able to give COVID-19 to others else once they get to 10 days from the start of symptoms. (The exception concerns critically ill patients in hospital.)
The CD nurse interviews the case to determine when symptoms started, how they may have been exposed, their travel history and, importantly, any close contacts who may have been exposed to COVID-19 while the case is infectious. As a precaution, contact follow-up also includes any close contacts in the two days before the case showed symptoms in order to take into account potential transmission in the pre-symptomatic period.
Most close contacts don’t become cases
Time and space are key factors in defining a close contact. The general rule of thumb is that those who have been face to face without physical distancing for a cumulative 15 minutes or more is considered a close contact.
“Because this is COVID, a lot of people are keeping their social circles small,” Enns said. “This means the list of close contacts tends to also be small.”
If someone is considered a close contact, the person is supposed to self-isolate for a 14-day period from their last contact with the person who is positive. If anyone is going to develop COVID-19, it will occur within 14 days, known as the incubation period.
Public health staff follow up daily. Many people are choosing daily electronic follow-up but phone calls are also an option. If someone develops symptoms, they arrange for testing.
A negative test will not shorten a close contact’s 14-day self isolation period as the contact is still in the incubation period.
“The majority of close contacts do not go on to become cases,” Enns added.
On Vancouver Island, public health staff are testing about 1,000 people a day, and about “99.9 per cent” do not have COVID-19, meaning staff are testing too many people with symptoms not predictive of the disease.
The most important elements here are identifying the actual cases, followed by the close contacts who might have been exposed and ensuring they are isolated for the necessary time.
“This stops transmission,” Enns said. “It stops it in its tracks.”
If societies can do this, according to Enns, it can help avoid measures such as lockdowns.
Close versus casual contact
Another thing to consider is the difference between a casual and a close contact.
“If you are not named by public health as a close contact, it should not keep you from doing the things you should be doing,” Enns said.
Many people now are worried about being a contact of a contact, and needlessly staying home from work or keeping their kids out of school. Enns emphasizes someone is only considered a close contact through exposure to a person who not only shows symptoms but tests positive for COVID-19.
If the rising number of cases in B.C. is alarming, the relatively low incidence on the Island is more encouraging. Vancouver Island has kept case numbers low and has, for months, been able to have people isolate themselves, and if sick, recover at home rather than in hospital.
Another challenge is terminology. All too often, Enns said, there is confusion in the media between “isolation” for those who become sick and test positive versus “quarantine” for close contacts of cases. If it seems like some game of semantics, it is because public health professionals want to be careful about asking people to stay home for 14 days because it is not an easy thing to do.
“Words matters, definitions matter,” Enns said, adding the term ‘self-isolation’ has evolved to cover both those in quarantine and isolation.
Role of businesses
There are other tools that can help with tracing contacts. Many businesses, especially ones such as restaurants or bars where customers might stay for an extended period, are following WorkSafe BC and using logbooks to get customer contact information. This can be helpful, Enns said, when regular channels to find out a case’s contacts are incomplete – in other words, when exposure comes through community transmission but they cannot pinpoint how a person contracted the disease.
“They have made our jobs so much easier for contact follow-up,” she said.
When the public gets a report about potential exposure at a particular business or on a flight, for example, this is how a notice is generated, but it’s not the first of line of defence. That remains with the public health working with those who test positive and their close contacts.
“Contact tracing let’s us have containment,” she said. “This is within our control.”
Evolution of knowledge
Enns also said shaming behaviour on social media toward people with the coronavirus or the insisting we hear about ‘every case in every place’ will only make it harder to get the right people to go for testing.
“We don’t need to police each other as citizens,” she said.
In the months since the pandemic was declared, the understanding of preventative measures, treatment and other factors has changed. Enns is concerned by the amount of misinformation circulating, and she reminds the public that the learning process for everyone, including people working in public health, is ongoing and the knowledge is evolving constantly.
“We’re in a pandemic where we know things are going to change,” she said. “We don’t have a playbook.”