Friday, April 24th 2020 at 10:15 am
Social distancing
requirements could have counterintuitive outcomes, according to one
study, which suggests the behavioral changes triggered by social
distancing could ultimately worsen the disease outcome and increase the
size of the final epidemic
During an epidemic or pandemic, public health officials may enforce
social distancing as a method to control the spread of a pathogen.
However, at least one study suggests the ultimate changes in contact
patterns triggered by social distancing measures could end up having a
negative effect on the population and, in some cases, even worsen the
outcome of the epidemic.[i]
The practice of social distancing
means keeping physical space between yourself and other people outside
of your home. The U.S. Centers for Disease Control and Prevention (CDC)
states that in order to practice social distancing, you must stay at
least six feet (two meters) away from other
people, not gather in large groups and avoid crowded places and mass gatherings.[ii]
people, not gather in large groups and avoid crowded places and mass gatherings.[ii]
According to the CDC, "Limiting face-to-face contact with others is the best way to reduce the spread of coronavirus disease 2019 (COVID-19),"[iii]
and various levels of social distancing requirements have been enforced
around the globe during the COVID-19 pandemic. However, as noted by
researchers in the Journal of The Royal Society Interface, "In general, it is hard to predict the effect of preventive measures without using models to guide us."[iv]
This is particularly true when it
comes to accounting for human behavior, which is often assumed to be
constant over time by standard epidemic models but, in fact, may be
quite dynamic, especially during a public health crisis.
Study Demonstrates Potential Negative Outcomes of Social Distancing
To determine whether social
distancing could have unexpected negative outcomes, researchers from
Stockholm University in Sweden and the U.K.'s
University of Nottingham used epidemic network models and existing
real-world networks. The results suggest that social distancing, when
conducted at a "high enough rate" at the start of an epidemic, may prevent it from occurring.
However, moderate social
distancing may worsen the disease outcome both in the initial phase of
the outbreak and in terms of the final epidemic size. As an epidemic
evolves, people may choose to distance themselves from those they know
are infectious. Models suggest that social distancing may even arise
spontaneously during an epidemic based on individual choices rather than
being centrally imposed.[v]
An individual may then choose to either drop the connection
completely or replace ("rewire") the connection with another individual,
perhaps because they desire to maintain a certain number of social
connections. This is where many of the negative implications arise, as
the study found that:
" … having individuals who rewire away from infectious neighbors and possibly replace them with new ties may be harmful for the community as a whole.Depending on the network structure of the population, social distancing may in fact increase the epidemic threshold parameter from below to above its threshold value, making a large outbreak possible where without social distancing it was not. We also show that social distancing can increase the final size of the epidemic."[vi]
While this didn't hold true for all networks, there were both
real-world networks and model networks that the researchers found had
worse outcomes when social distancing was in place. This means,
according to the researchers, that social distancing may have
"counterintuitive consequences for the population-level."[vii]
Further, they noted, "Public health interventions that aim at changing individual behavior through social distancing could have adverse consequences,"
using the example of school closures, stating that while such closures
reduce social contacts between the children and their schoolmates, some
of these contacts may be replaced by contacts outside of the school.
"As
our results show, it is not necessarily straightforward what effects
such behavior may have at the population level, where much may depend on
the disease and population under consideration," they noted.[viii]
This echoes a 2012 study
published in BMC Public Health, which similarly found that social
distancing can backfire, particularly if not done at a "drastic"
level at the very start of an epidemic, at which point foregoing
control and allowing the epidemic to run its course is preferable.[ix]
In some cases, social distancing can contribute to the "worst outcome," according to the BMC Public Health study, when control is attempted but not at the level that suppresses the epidemic:
Consequences of Social Distancing Cannot Be Ignored"If a disease is very highly infectious, social distancing may have no effect, or may require an unfeasibly high degree of caution in order to be effective. In these cases, doing nothing will be a more cost-effective strategy than using social distancing, because the worst-case outcome arises if the control is applied, but the level of caution used is too weak."[x]
Aside from its effects on the
spread of pathogens, there are adverse consequences of social
distancing, like resulting social isolation, that are worthy of
attention. At least 13 studies demonstrate that social isolation increases mortality risk, while having fewer social ties may increase your susceptibility to viruses like the common cold.[xi]
Social isolation also increases inflammation in your body,[xii] making you more vulnerable to inflammation-linked chronic diseases like cancer and, ironically, possibly increasing your predisposition to lung infections like pneumonia.[xiii]
It's clear that infectious disease dynamics are complex and only beginning to be understood, and seemingly straightforward "solutions" like social distancing do not have straightforward effects. In some cases, it may even worsen, not improve, epidemic outcomes.
References
[i] J R Soc Interface. 2018 Aug; 15(145): 20180296.
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