New data reveals the moving out of densely populated cities is a more impactful strategy than closing borders at decreasing the spread of the COVID-19 virus.
Image Credit: Massimiliano Zanin
Densely populated areas encourage the spread of viruses
Densely populated areas provide breeding grounds for viruses that are spread via close human interaction. The main routes to transmitting the SARS-CoV-2 virus are via breathing in the droplets produced by an infected person (such that are produced by a sneeze or cough), and via coming into contact with infected surfaces where someone may touch an object or even the hand of an infected person and then contract the virus by touching their face, eyes, mouth or nose.
These two main routes to transmission are more likely in crowded cities than they are in rural communities. Densely populated areas feature crowded public transportation, shops, and pathways, whereas rural areas allow people to be much more spread apart.
During the COVID-19 pandemic, there have been significant efforts to maintain distance between people and prevent situations where overcrowding can take place. However, this is less possible in densely populated urban areas. It is, therefore, reasonable to assume that migration from densely populated urban areas to sparsely populated rural ones may be an effective strategy at reducing transmission of the COVID-19 virus.
A major strategy that governments worldwide have tended to opt for is the closure of borders and the restriction of movement within their own country. Given the widespread closure of borders and travel restrictions as a major COVID-19 prevention strategy, researchers recently explored whether this limit of movement was effective at reducing the spread of the virus.
Researchers Massimiliano Zanin and David Papo conducted a study to investigate the efficacy of travel bans at preventing the spread of pandemic disease, in particular, the team focused on investigating the migration of people from large cities to smaller ones.
Closing borders “almost always bad”
The results of the study were surprising. They found that closing borders were almost always bad, and that allowing movement may be effective at reducing the spread of infectious disease. Zanin and Papo used simulations to collect their data. They placed a simulated group of people in two locations.
Then, they used SIR dynamics, a type of simulation that is often used in epidemiological studies of disease movement and stands for susceptible, infected, and recovered, the groupings given to classify people in terms of disease status to track disease movement. Using this method, the pair of researchers found that closing borders, according to Zanin, is “almost always bad”.
After running 10,000 rounds of the simulation, the researchers were able to confirm that migration from large cities to smaller towns was effective was at reducing the spread of the disease. While they admit that it does put those in the small towns at a likely increased risk, overall, this does not outweigh the benefit of reducing the population density in the larger cities.
In the scenario of a global pandemic, migration from cities to towns would likely have better outcomes for the entire population overall.
Zanin summarizes this sentiment, stating that "a collaboration between different governments and administrations is an essential ingredient towards controlling a pandemic, and one should consider the possibility of small-scale sacrifices to reach a global benefit”.
The results from the current study may help to inform governments and policymakers on how to develop effective strategies to prevent the spread of COVID-19. Currently, travel restrictions are in place all over the world. These findings may enable people to move around more freely without the risk of increasing COVID-19 transmission.
We asked Dr. Zanin if the spread of COVID-19 could have been reduced if more research had been undertaken into the effectiveness of shutting borders during a pandemic.
His response was the following;
We cannot know for sure, as the spreading of any disease is the result of many variables, many of them not even under our control. Still, any research is useful, even if the outcome is a negative result. And indeed the issue of whether closing local borders is a good strategy, is something far from being clear and it deserves more attention. "
- Zanin, M. and Papo, D. (2020). Travel restrictions during pandemics: A useful strategy? Chaos: An Interdisciplinary Journal of Nonlinear Science, 30(11), p.111103.