As the tracking of social contacts is considered an increasingly strategic tool to fight the coronavirus (COVID-19), different measures are being implemented to carry it out. But technological monitoring via smartphone is not the only way to do it. The city of San Francisco has created a task force to interview all COVID-19 positive individuals and track their interactions. The objective is to discover who infected them and who else they have been able to infect, in the hope of being able to isolate infected patients, alert those possibly exposed and, ultimately, stop transmissions.

The city’s Department of Public Health is expanding its staff with dozens of researchers, medical students, and other members of the University of California, San Francisco (UCSF), and could include other types of public workers. Municipal health care began tracking contacts to a limited level and are expanding it as the weeks go by. The team was born with around 40 people and could grow to 150.

In addition to the interviews, the task force is also offering the necessary support to ensure that all those infected are completely isolated, even helping them to seek refuge if necessary. They also try to locate between three and five people with whom the patients have been in contact in the previous days to alert them that they may be infected. In this way, they ask them to limit their social activities and encourage them to undergo a diagnostic test. Again, those who test positive will enter the process of interviewing and tracking their own contacts. 

UCSF Assistant Professor of Infectious Diseases and coordinator of the university’s contributions to this initiative, Michael Reid, explains: “Basically, we realized that if we want to do more than just confinement, we need a strong sustainable containment strategy and can identify each new case and their contacts. This should work at least, in the medium term, until we have a vaccine.”

In the USA, where strategies against COVID-19 depend mainly on states and cities, the San Francisco Bay Area has been one of the first regions to adopt aggressive measures to stop the outbreak, and it appears to have already managed to flatten the disease curve. But it still registers hundreds of new cases a day, and the number of deaths continues to rise.

The new coronavirus is highly contagious and, although we still do not know its reproductive rate, it is estimated that, without measures of social distancing, each infected person infects between two and three more people. If according to the highest estimates, COVID-19 has a reproduction number of 3, a positive case could become more than 59,000 cases in 10 rounds of infection, Reid points out. “So you should find other contacts as quickly as possible and tell them to stay … at home,” he says.

Other places, especially Massachusetts, have also started major tracking efforts to identify and contact thousands of citizens who may have been exposed. But the modus operandi of the Bay Area could offer crucial lessons or warnings if he can help curb the current spread and prevent large outbreaks following.

A quick and energetic response

The San Francisco Bay Area recorded some of the first cases of COVID-19 in the U.S. as well as the first signs that it was spreading, with a case of unknown origin from February 26. On March 16, six counties ordered nearly seven million residents to be confined to their homes for weeks. Three days later, California became the first state to implement these measures across the country, when its governor, Gavin Newsom, ordered nearly 40 million people to stay home.

The measures appear to have helped. The number of daily deaths in California appears to have reached and reached zero in mid-May, according to the model for each state of the University of Washington. But the Bay Area’s success in slowing down the spread would also mean that a large part of its population would not be immune, and the region would become especially susceptible to the reintroduction of the disease from other areas that have not taken such vigorous measures, such as Texas, says UCSF epidemiologist George Rutherford, adding: “We will have to keep tracking like hawks.”

Increasing the number of diagnostic tests will also be critical to monitoring contacts effectively, as researchers should be able to perform all people with symptoms, as well as those who came in contact with it, and obtain results quickly. To support that effort and contain the outbreak locally, San Francisco should be able to run up to 130,000 tests a month, Rutherford estimates.

It is not known how many tests the city can currently process, but the number is increasing. The collaboration between UCSF and Chan Zuckerberg Biohub started by processing 2,000 samples a day and wants to reach 4,000. 

The role of technology

Tracking contacts is an arduous manual task, which means that it is sometimes impossible to locate all infected and their contacts during outbreak peaks. But there are some tools and technologies that can help.

The working group is using a telephone and online contact tracking application developed by Dimagi to manage cases and for constant attention. Among other things, the system will send text messages daily to potentially exposed people, asking them if they have developed symptoms. If the answer is positive, workers will start to follow up and offer additional advice.

The team will also ask patients for permission to view their phone’s location data, which would help create a more complete picture of where they’ve been and the times when they may have been found in crowded places. But without access to the phone data of the entire population, the team will not be able to find out when they were infected or who those people were.

Countries like China and South Korea took more aggressive measures to monitor the movements of their population during the pandemic, requiring citizens to download applications and entering sources of personal data. There is no doubt that this strategy was one of the keys that allowed Asian countries to automate and massively scale up contact tracking efforts. China reportedly identified more than 700,000 people who had been in contact with the infected and suspected cases, as well as tens of thousands of those infected.

However, given privacy laws and concerns, the limits on what kind of location data US health officials may use. The federal government and research groups are exploring a  variety of ways  to introduce voluntary, anonymous digital contact tracking, using mobile phones, apps, and other tools. Among other things, this could indicate to people if they have passed near an infected person.

But it is unclear whether a critical mass of the population will decide to download these applications, according to University of Washington law professor and digital privacy specialist Ryan Calo. If few people sign up for such follow-up efforts, that could undermine their effectiveness, to say the least, and even give some users a false sense of confidence about where they could safely go outside, he explains.

Constant social withdrawal

But no matter how much the regions rapidly accelerate contact tracing and test execution, and decrease their number of infections and deaths, life will not return to normal any time soon.

Rutherford believes to soften his containment rules, mitigation measures will have to be replaced by “big containment” ones. Among other actions, according to him, the high-risk population, like the elderly, must remain at home and the rest of the population will have to wear face masks in public spaces and stay at least one meter away. In different buildings, workplaces, and restaurants, precautions will also need to be taken to keep people safe and separate, clear tables, space shifts, and provide hand sanitizer at entrances.

Regions may also need to carry out other generalized tests (antibody or serological tests that indicate whether a person has been infected before) to better understand how large a second outbreak could be and what kind of continuous efforts will be required before to soften other standards, highlights professor of epidemiology at Ohio State University, William Miller.

But it is very likely that even with all these measures, outbreaks will continue to appear. If different areas hope to keep contamination low and save as many lives as possible, citizens and politicians will need to be ready and willing to quickly switch between the strictest and most flexible measures, possibly for many months to come. Rutherford concludes: “We will be able to return to normal when everyone receives the vaccine, but until then, no.”