Keeping out COVID-19 in Newfoundland

By Dr. Liji Thomas, MDJul 21 2020

One of the most striking phenomena concerning the current COVID-19 pandemic was the closing of intra-national and international borders on a scale unheard of in recent history. Such travel bans became a crucial point in combating the spread of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and thus containing the outbreak to a locality.

However, when is it the right time to reopen borders? Is it when there are no more local cases? A new study published on the preprint server medRxiv* in July 2020 shows that travel restrictions are highly effective in preventing future outbreaks.

Study: Is it safe to lift COVID-19 travel bans? The Newfoundland story. Image Credit: Alexandar Iotzov / Shutterstock

This news article was a review of a preliminary scientific report that had not undergone peer-review at the time of publication. Since its initial publication, the scientific report has now been peer reviewed and accepted for publication in a Scientific Journal. Links to the preliminary and peer-reviewed reports are available in the Sources section at the bottom of this article. View Sources

The Study: Impact of Reopening Borders on Newfoundland

Newfoundland and Labrador make up a Canadian province that has not reported a single COVID-19 case since the second half of April 2020, after having had 261 cases of which 3 died. On July 3, 2020, not having had any new cases for 36 days, air travel resumed within the Atlantic Bubble, comprising the corridor between the four provinces on the Atlantic seaboard. These are Newfoundland and Labrador, Nova Scotia, New Brunswick, and Prince Edward Island. Air travel between these provinces will not require travelers to be quarantined on arrival.

Public pressure is on to open up the borders completely. Thus, leadership-level decisions now have to be made on how to accomplish this given the possibilities of either perfect quarantine or quarantine violations.

The province of Newfoundland and Labrador is sparsely populated, with just about 520,000 inhabitants. Over 90% live on the island of Newfoundland and the rest on Labrador on the mainland. Its populace has the highest rates of obesity and overweight, metabolic disease, and cancer, as well as smoking and other markers of an unhealthy lifestyle.

The Basic Questions

The first COVID-19 case was on March 14, 2020, followed by a spike caused by a superspreader. However, the outbreak was rapidly controlled, and no fresh waves occurred since then. This means that any future cases will be imported from outside. Given this, the health policy has been that only residents, workers, and those having special permits will be allowed to enter the province.

About 75% of all entering travelers do so by air since there are only a few entry points into the province. The current study, therefore, chose to assess the impact of travel bans on the risk of importing disease by using passenger flights. The questions to be answered include the effect of the Atlantic Bubble, how further opening to the other Canadian provinces and the US would affect Newfoundland, and how quarantine violations will affect the outcome.

The study uses a method of modeling that will allow mobility between various local populations to be observed and prediction of the parameters based on reported case data as well as real-time updating of these parameters. The researchers thus first developed a local epidemiological model and then added in air traffic from first the Atlantic Bubble only, then all of Canada, and then all of the continent.

The Changing Conditions of the Outbreak in North America

As of July 1, 2020, the largest exposed population is in Florida and Arizona, followed by South Carolina, Nevada, and Texas, ranging from 0.134% to 0.065%. The largest infectious population on the same day was in Arizona, Florida, South Carolina, Nevada, and Texas, from 0.25% to 0.11%. In contrast, exposed or infectious populations in Canadian provinces have never crossed 0.011%.

Secondly, on the day of reopening, the effective reproduction number R(t) was largest at 2.15 in Florida and ranged from 2.1 to 1.8 in Nevada, Montana, Idaho, and Delaware. However, in Canada, it was possible to calculate this index only in Alberta, British Columbia, Saskatchewan, and Ontario, ranging from 1.3 down to 0.33. Newfoundland and Labrador, the other Atlantic provinces, and other territories had so few cases that no R(t) could be assessed. Instead, the population-weighted mean effective reproduction number for Canada and North America is used for the predicted reopening in Newfoundland and Labrador.

Exposed and Infectious Travelers

Most exposed and infectious travelers are from Florida and Texas, Nevada, Alberta (exposed only), Quebec (exposed only), and Ontario. With a full reopening of air traffic under July 1 outbreak conditions, the researchers estimate that 0.2 and 0.33 exposed and infectious travelers will enter the province every day. In other words, one infected case may be expected every 3 days, and an exposed individual every 5 days, on average.

Quarantine vs. No-Quarantine

The researchers also estimate that if there is 100% quarantine of all incoming travelers, vs. 50%, vs. 0%, the effect is predicted to be zero, a mild outbreak of new cases, and a rapid exponential outbreak. If the province is reopened to the Atlantic Provinces, to all of Canada, or to all of North America, the effect is a non-significant increase in new cases in the first two scenarios, but a rapid exponential rise in new cases in the third.

Travel Restrictions

When the researchers compared the effects of a travel ban vs. quarantine, using the population-weighted mean reproductive numbers for all of North America and for all of Canada, they found that with no quarantine and no travel restriction, 0.1% of the population would be affected by COVID-19 after 38 or 39 days respectively. With 50% quarantine, the lag time increases to 46 or 48 days, respectively. With 95% quarantine, it is 80 and 92 days, respectively.

If travel is banned within Canada, this lag period increases to 97 and 125 days. If travel is allowed only within the Atlantic Bubble, the time goes up to 102 and 132 days.

What This Means for Future Travel Bans

While many people fiercely resent the imposition of travel bans, it is a very effective way to counter the spread of the pandemic. In conjunction with a ban on large gatherings, some states or provinces have eliminated current cases. The best way would be, therefore, to keep these provinces free by cutting its travel links with the outside world. However, this curtails freedom of movement and maintain economic constraints.

The researchers comment, “From an outbreak dynamics perspective, the picture is quite clear: Without proper control, an influx of infected travelers can easily become the seed for a new exponential outbreak.”

Thus, reopening plans are being made, two of which are analyzed in the current study. This can be extended to any region in which there have been no fresh cases for over two months.

Since the pandemic case number changes continuously outside the province with zero cases, the reopening strategy must also be subject to constant change. Beginning with a seven-day average of 1717 new cases in Canada, on May 4, 2020, it went down to 311 by July 1, 2020. In Nova Scotia, one of the Atlantic provinces, it began at 12 and dropped to 0.3. The other Atlantic provinces had low rates of infection throughout the whole period.

Overall, therefore, Canada shows a slowing trend with respect to new cases, unlike the USA, and community transmission in all the Atlantic provinces is minimal.

Opening Up to Canada Vs. to The Whole of North America

This data shows that travel within the Atlantic provinces is unlikely to push up cases, travel from the rest of Canada might increase cases to a mild extent because of the current low case numbers in these provinces. However, with states like California, the travel frequency is low, but the case number high. This suggests that removing travel restrictions between Newfoundland and all of North America would expose the former to an unreasonably high risk of exponential spread.

The researchers also point out that with the 3 day and 5 day frequency of exposed and infectious traveler entry, “every other day, a new COVID-19 case would enter the Newfoundland and Labrador via air travel.” Without rigorous quarantine requirements, this will inevitably lead to spread as such individuals are notoriously asymptomatic or presymptomatic for the most part.

Conclusions

The study authors say, “The forecast confirms our intuition that there are two strategies to prevent a new outbreak, either mandating strict quarantine requirements or limited travel within the Atlantic Bubble.” Beyond 60 days of reopening, predictions become unreliable, and there is every chance of the outbreak going out of control within weeks.

The prediction of the time period required for over 0.1% of the population to be infected suggests they say, “that, under current conditions, banning air travel from outside Canada is more efficient in managing the pandemic than fully reopening and quarantining 95% of the incoming population.”

The only alternative is strict and universal quarantine regimes for all incoming travelers, or universal testing, tracing and contact isolation policies. The study concludes with the warning that laxity in reopening and quarantine efforts could result in a ballooning outbreak within weeks. This would take extensive efforts and much money to contain, via lockdowns and other unpopular non-pharmacological interventions.

This news article was a review of a preliminary scientific report that had not undergone peer-review at the time of publication. Since its initial publication, the scientific report has now been peer reviewed and accepted for publication in a Scientific Journal. Links to the preliminary and peer-reviewed reports are available in the Sources section at the bottom of this article. View Sources