Shorter quarantines could actually help prevent COVID-19 outbreaks

Two-week quarantines strain mental health and finances. New research shows weeklong restrictions could ease this burden and improve contact tracing.

A medic asks photographer Justin Jin to read out his temperature through his hotel door during a twice-daily check as part of his 14-day quarantine after arriving in Shanghai, China, from Belgium. The picture was taken through the door’s peephole. Jin made the arduous journey to see his father, who just had surgery.

When photographer Justin Jin’s father experienced a medical emergency in late November at home in China, Jin, who lives in Belgium, immediately booked a flight to be with him. But the COVID-19 pandemic turned the usually straightforward trip into a two-and-a-half-week ordeal.

In China, the virus is now well-controlled, so the government has set up a series of carefully choreographed precautionary steps to keep travelers from reintroducing the disease. Forty-eight hours before hopping on his flight, Jin had to take two types of COVID-19 tests—one for antibodies that involved a finger stick and a genetic test involving a nasal swab.

The results were uploaded to an app for the Chinese embassy to approve before he could board. On the flight, all the flight attendants wore personal protective equipment from head to toe. Passengers were given another test on arrival and then whisked to a quarantine hotel, where they would stay under strict surveillance for 14 days regardless of their test results.

The hotel quarantine was strict: each passenger was isolated in a room, and the doors were surveilled with a camera so that security would be alerted immediately if anyone stepped out. The rooms and hallways were fumigated every time a new arrival walked by. Meals were delivered to the door, and doctors came by twice a day for 14 days to do temperature checks. Jin was given a bucket and a supply of disinfectant to sterilize his toilet before flushing it.

“I felt like I was a specimen being abducted into a UFO because everyone was treating me with such caution,” Jin says.

Jin’s experience speaks to the frustrations experienced around the world since 14-day quarantines became the norm with COVID-19. While caution is wise, researchers are now wondering if such lengthy measures are necessary and are uncovering shorter alternatives that retain public safety. Quarantines are costly, straining the mental health and finances of those in isolation, as well as the resources of governments and companies implementing these precautions. Shorter quarantines could ease that burden, but this pivot will also require better logistics such as spaces where people can quarantine, access to fast testing, and support for meals and other necessities like medicine. Making these investments could potentially increase people’s compliance with voluntary guidelines.

This push for shorter quarantines is supported by academic reports that show that people with coronavirus don’t appear to be contagious after nine or 10 days. In addition, new research shows that shorter quarantines combined with smarter testing strategies can actually do more than 14-day quarantines to reduce the risk of COVID-19 transmission.

These new studies explain why, on December 2, the U.S. Centers for Disease Control and Prevention announced two new options for quarantining. The CDC still recommends 14 days when possible, but if a person still has no symptoms and tests negative on day five or later after potential exposure, they can end their self-imposed quarantine after a week. Alternatively, if a person lacks access to testing, they can exit quarantine after 10 symptom-free days.

The main reason that people fail to quarantine for the recommended duration is lost wages, especially in the United States, where many workers do not have sick leave, explains Maimuna Majumder, a computational epidemiologist at Harvard Medical School. With a few exceptions (such as the state of Vermont), governments in Europe and North America have not done enough to support those who are not able to quarantine because they would incur financial loss or they live in crowded housing, adds Müge Çevik, an infectious disease physician at the University of St. Andrews in Scotland.

"Income relief is very important. There's been a lot of emphasis on testing, but we haven't emphasized enough supported isolation," Çevik says. "Self-isolation has been left as the weakest link in the test and trace programs all around the world."

Understanding the course of infection to compress quarantines

Aside from shaving a few days off confinement, reducing the length of quarantines may help prevent coronavirus clusters before they happen. Recently, researchers at the Yale School of Public Health, led by biostatistician Jeff Townsend, developed mathematical models showing just that. They found that strategically combining COVID-19 testing with a shortened quarantine can ease the burden for people who have potentially been exposed.

A quarantine is only successful if it catches positive cases during the period when they’re most infectious. Yale’s work relied on new data about the incubation period of SARS-CoV-2, or how long people take to develop symptoms after being infected. It also looked at what researchers have learned this year about how the ability to transmit the virus to others changes over the course of the illness and how that compares with the viral load, the amount of detectable germ inside a person’s body.

Before the summer arrived, scientists had a rough idea that the SARS-CoV-2 viral load increases exponentially after exposure, peaking after five days and then slowly decreasing. Symptom onset also typically occurred around this five-day mark. However, reports also showed that cases transmitted the coronavirus two to 10 days after exposure, raising questions about whether the sweet spot for detecting virus and symptoms—five days—could truly define when people are most infectious.

Incorporating such information, the Yale team reports in a preliminary study that an eight-day quarantine with polymerase chain reaction (PCR) testing on entry and exit is as good or better than a 14-day quarantine without testing in terms of preventing coronavirus spread. One caveat: The test needs to be administered on the seventh day of the quarantine, with results arriving within 24 hours, given what’s now known about the incubation window and infectiousness.

The Yale researchers tried this strategy in real life—at two offshore oil-and-gas rigs owned by the Australian company BHP. The tight confines of an oil rig are an ideal place for a highly transmissible disease to thrive. But shutting down to control an outbreak would be hugely expensive and could cost the company millions of dollars, so it was motivated to find an optimal way to keep its workers safe and keep operations running.

Prior to the study when little was known about the coronavirus, BHP would test all its employees before they entered a three-day quarantine.

Starting in June, one rig moved to five-day periods, while the second rig extended their quarantines to seven days beginning in August. Testing was performed when people entered quarantine and again when they were scheduled to exit.

By looking at staggered scenarios, the team showed the entry testing alone missed a bunch of cases. Exit screening during the 5-day plan caught a third of the total positives. For the seven-day option, the proportion rose to half. Overall, these strategies caught 16 infected crew members from heading to the offshore rig, and follow-up testing after 11 days unearthed zero positive cases. When the team calculated the potential benefits, they predicted that a seven-day quarantine with entry and exit testing could prevent 98 percent of post-quarantine transmission.

The takeaway, according to Townsend, is that a negative test when someone enters quarantine can produce a false sense of security, and testing when they were supposed to exit was the key to catching infectious individuals and keeping them in self-isolation. Based on his team’s result, it was not helpful to defer testing beyond seven days. Townsend says their plan was so successful that other oil and gas companies have implemented similar policies.

The Yale experiment also revealed an important lesson for those who may be preparing to visit with extended family and friends over the holidays. Aside from quarantining as long as possible beforehand, Townsend recommends waiting to get tested until right before visiting your family. If you test too early in the course of infection, the viral load may be too low for detection and you'll get a false negative result.

Another preprint study, by researchers at the London School of Hygiene and Tropical Medicine, found similar results when investigating strategies for international travelers: an eight-day quarantine after arrival, with a PCR test on day seven, achieves a similar reduction of transmission risk as a 14-day quarantine without testing. Moreover, a comprehensive analysis of studies released to date that Çevik and her colleagues published November 19 in The Lancet Microbe confirmed the incubation window for SARS-CoV-2—but also showed that COVID-19 cases don’t produce viable virus after nine days of illness, further backing the motivation for shorter quarantine windows.

Shorter quarantines, easier contact tracing?

Shorter quarantines could also increase the effectiveness of the third pillar of infection control: contact tracing. People are sometimes hesitant to tell contact tracers about their social lives. In addition to the fear and stigma associated with admitting to high-risk activities, there's a lot of pressure in naming your friends knowing they will be asked to self-isolate. In the United Kingdom, for instance, the current testing and tracing system captures only about 20 percent of contacts, and they are mainly household contacts; the system is failing to find a lot of people who are potentially afflicted.

"This whole system can't really work without having a supported isolation or quarantine, because it fails in every stage," Çevik says.

She posits that focusing on the contacts that have the highest risk of being infected and spreading the virus might be more effective than doing blanket contact tracing. Almost 80 percent of secondary infections are linked to 20 percent of cases. "We don't necessarily need to reach all the contacts of all the cases,” says Çevik, but rather, officials could prioritize those most likely to spread the coronavirus onward.

In a recent working paper, Majumder and a postdoctoral fellow Andrew Perrault did exactly what Çevik suggests. Their goal was to reduce the total number of quarantine days by replacing blanket guidelines with a risk-based approach. The duration of quarantine would depend on the contact's chances of acquiring the infection and transmitting it to others.

"The idea of the risk-based quarantine system is to observe contacts of a certain individual for symptoms,” Perrault says. If symptoms arise, that's evidence that a person is highly prone to transmission and makes it much more likely that other contacts from the same exposure event are going to develop symptoms later, he adds.

Typically, a confirmed COVID-19 case provides contacts to a tracer, who then reaches out to all those people and asks them to quarantine for two weeks. Under a risk-based system, a contact tracer keeps track of everybody who was exposed at a specific event. If some of those individuals become symptomatic, then all must continue their quarantine. But if none develop symptoms after a couple of days, then the risk that any of them are infected is low, and they can all be released early.

"The advantage of this approach is that you get more transmission reduction at the same number of quarantine days because you're going after the biggest spreaders first," Perrault explains. This approach also increases the motivation to comply with quarantine: If a person knows that another contact of the same source developed symptoms, they are going to be less likely to drop out of quarantine, Majumder explains.

Using a computer model to simulate transmission, Perrault and Majumder predict that a risk-based quarantine, especially when combined with exit testing, can reduce the number of quarantine days while keeping the risk of transmission low: Under the old CDC guidelines, the sum of days spent in quarantine for all contacts connected to an initial spreader is, on average, 62.1, whereas under the risk-based plan, that number is reduced to 36.1 days.

The bottom line for holiday travel, though, is that best practices may not differ a whole lot from the CDC’s original recommendations because these new approaches require resources that are not universally available, such as testing with fast turnaround times, robust contact tracing staff, and buy-in from local leaders.

"The deal here is that if you want to gather with friends and family outside of your quarantine pod or outside of your household for the holidays, you still need to quarantine for two weeks. That's really what it is," Majumder says.

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