Coronavirus Series: What is the science behind the 14-day quarantine?

A closer look at the numbers, and what it might mean for UCL students.

Source: Flickr

Summer 2020 has proven to be a summer like no other. Countries are continually being added and taken off the UK’s quarantine exemption list, airlines are laying off thousands of staff and the public are struggling to work out what holidays are viable in the current climate.

At the centre of this is the 14-day quarantine period, where those who travel to the UK from abroad, unless it is an exempt country, are not allowed to leave the place where they are staying for the first 14 days after arrival (known as self-isolating).

It is vital to the government’s plans to control the virus, but has proved to be disruptive to many lives. Here, we look at the science and rationale behind this measure and ask: could another approach be better? 

Why 14 days?

Fourteen days is a “long-standing” public health practice according to Lindsay Wiley, a professor at American University’s Washington College of Law. 

This is related to the time period in which the virus, once it infects someone (a host), replicates and makes enough copies of itself that the host would shed the virus. This period of time between infection and the onset of symptoms is what is commonly referred to as the incubation period.

Researchers have found that the median incubation period for Covid-19 is about five days. However, they also estimated that 99 per cent of those infected would develop symptoms after 14 days of active monitoring or quarantine. That is to say, it could be as long as 14 days between when a person was exposed to the virus and the onset of symptoms. Crucially, it is unclear how much asymptomatic infection (Covid-19 positive individuals who are not showing symptoms) is contributing to the spread of coronavirus; this may have been behind the reasoning for this “safety” window.

Can we not just test at the airport? 

There has certainly been a call in recent weeks for testing to be done at UK airports. Indeed, Heathrow airport announced on  August 19 that it had set up a dedicated Covid-19 testing facility which guaranteed passengers would receive their results just hours after being tested. Under this system, the first test would be taken at the testing facility on arrival, with a second confirmatory test to follow a few days after the first. If both tests were negative, new arrivals in the UK could be excused from their mandatory quarantine before the 14 days are up.

Last week, the government’s Scientific Advisory Group for Emergencies released papers from Public Health England that showed testing travellers on arrival in the UK and five days into a seven day quarantine could prevent 85 per cent of travellers who are infected but asymptomatic from potentially introducing infections into the UK. They also suggested that a slightly longer period of 10 days of isolation, as opposed to the initial guideline of seven days, could produce similar results to the current 14-day quarantine. However, there are several assumptions that have to be made in order for this to work - including tests working perfectly, which is not always the case, with an estimated 24 per cent of tests producing false negative results. 

This has added to evidence from a model published by the London School of Hygiene and Tropical Medicine (LSHTM) which suggests that ensuring people quarantine for eight days and testing people on day seven could cause a similar reduction (94 per cent) in infectious travellers being released into the community to that of a 14-day quarantine (99 per cent).

Still, they also found that requiring a 14-day quarantine period would likely result in less than one infectious traveller entering the UK per week from the EU and USA. The risk of transmission is also highest from pre-symptomatic travellers, who may not isolate as they would be unaware that they are Covid-positive, which could be mitigated by a quarantine. 

What are other countries around the world doing?

Generally, most countries who have mandated a quarantine have defined it as 14 days long, as recommended by the World Health Organisation.Such countries include Canada, China and South Korea. 

The countries that are on the UK exemption list are currently determined by the number of cases. If there are over 20 cases per 100,000 people over seven days, the country is not exempt from the quarantine. This ruling has precluded countries such as France from being a quarantine-free destination in recent weeks. 

New Zealand, which has been lauded for its strict approach to the pandemic, requires all arrivals to spend 14 days in government-managed isolation, and are tested for Covid-19 on day three and day 12 of their stay. Their caution has been because shorter quarantine periods, or relying on testing only with no quarantine, substantially increases the risk of releasing an infectious case, which, under their current method is about 0.1 per cent per infected arrival. 

Most countries are following a similar procedure, but recent evidence from the same working group at the LSHTM suggest that imported cases account for less than 10 per cent of all cases in 103 out of the 142 countries looked at. “Strict untargeted travel restrictions are probably unjustified in most countries [unless they] have both good international travel connections and very low local Covid-19 incidence,” concludes the paper. 

What is happening at UCL? 

UCL students have been facing these problems across the world as they hurry to make it back in time for the start of term. One UCL student in Portugal booked a flight two weeks before the start of term, only to find out that Portugal had been added back onto the UK’s exemption list on the day of their flight.

Another UCL student lamented that she “had no summer,” having been forced to quarantine for two weeks coming from Dubai. “The irony is that Dubai’s cases have been much lower than the UK,” she said, “and I took a test before I boarded the plane as per their policy so I’m almost certain I don’t have it.”

A final year UCL student spoke of how they were unable to spend time with their family in Australia before the start of term, with “one two-week quarantine when [they] arrive, then another quarantine when [they] travel to the state in which their parents lived, and the threat of another quarantine in the UK.” Instead, he is hoping he might get a chance to see his family next year.

Still, the UCL students that spoke to Pi Science & Tech found it helpful to understand the rationale behind quarantine recommendations which have become a new reality for many. Many expressed an understanding that in order to keep levels of the virus at a low in the community, such measures will need to continue to be enforced. 

UCL has advised students returning from countries not exempt to arrive in the UK between September 7 and September 11. There may be a need to quarantine in temporary accommodation provided by UCL before moving into allocated UCL accommodation, but will only begin charging for accommodation from September 26. 

UCL students planning on arriving before September 26 in order to quarantine should submit an Early Arrive Request online, after which UCL accommodation will confirm whether the request can be met, and place the student in accommodation for the quarantine period. Students will need to pre-book a time slot in advance for the planned check-in date to allow social distancing measures to be followed. Those who have symptoms or share a household with someone showing symptoms should not travel to the hall, and instead rearrange a start date to the contract. Students will be able to order essential items online, such as meals and sanitary items between 8:30am and 8:30pm which will be delivered directly to their room. 

Unless the 14-day quarantine period is changed, this seems the new reality for many at UCL, and across the world.