The Virus as Complex Adaptive System

29 December 2019:  Chinese authorities first identified similar clusters of ‘pneumonia’ cases in Wuhan.

30 January 2020:  9 776 confirmed cases of coronavirus worldwide

According to the Johns Hopkins website, the current coronavirus numbers reflect 156 400 confirmed cases and 5 833 deaths globally (11am GMT time, 15/03/2020) – totals that will be outdated by the time this post goes live.

Since the beginning of this year global governments, organisations and institutions have worked closely with medical scientists and specialists to better understand and fight the spread of the coronavirus.  In addition, there has been a remarkable acknowledgment of the importance of complexity science and the consideration of the characteristics of complex adaptive systems in studying COVID-19 and even viruses in general before that.

Viruses as Complex Adaptive Systems

Little did Ricard Solé and Santiago Elena know of the pandemic that would manifest itself less than a year after their seminal work was published as part of the series Primers in Complex Systems.  Their book Viruses as Complex Adaptive Systems highlights the new understanding complex system theory is providing on the adaptive dynamics of viral populations and also provides further context to viral origins and their evolution.  Viruses emerge continuously and also frequently evade our immune systems, which highlights their evolutionary potential and ability to adapt to any environmental challenges.  Solé and Elena provides a cohesive framework for understanding viruses as complex adaptive systems and show how new insight into virus development is provided through the application of complex systems theory.


The book addresses questions such as the following:

  • What exactly are viruses, how did they originate and are they living entities?
  • How similar are computer viruses to their living counterparts?
  • How complex can they become?
  • What is their role in shaping the evolution of complex organisms and what role have they played in the development of society?
  • Why are there so many new emergent viruses and how do they emerge?

The following quote provides for a fascinating introduction to a very timely project by Solé and Elena:

“Viruses have shaped the evolution of cells, organisms, ecosystems and even the biosphere. Such influence spans all scales of biological organization, from genomes to the planet. Their dynamics involve nonlinear phenomena, tipping points and self-organization processes that have many commonalities with other biological and nonbiological systems. Such similarities might hide universal properties that pervade complexity, and in this respect, viruses offer a unique window into the origins of complex systems.”  (Solé and Elena, 2018)


Complexity and COVID-19

Further work is also undertaken internationally through a complex systems approach to fight the spread of COVID-19.  Yaneer Bar-Yam and his team at the New England Complex Systems Institute have taken a stand from the very start to assist in distributing knowledge and information on the subject, but also to advise governments, businesses and even families via useful guidelines at

Yaneer was interviewed recently and made a number of important and also very thought-provoking points.  He emphasised that it is really important for people to understand the power of exponential growth in extreme events like the coronavirus and also the amount of physical and economic harm it does if action is delayed.  Yaneer based his discussion around two main subjects:

  • Not Learning from the past

Yaneer made it clear that past experience is not a good indicator at all for future events when it comes to the coronavirus.  People might consider predicting the likely spread and consequences of the coronavirus by looking at a historical events, such as the Black plague or Spanish flu.  Hence, past experience and the accumulated statistics of past events are believed to be sufficient for predicting future events that will be experienced – that the sizes of the Ebola and SARS outbreaks would be the same in future, for example.  It is suggested that this is wrong, as conditions and dynamics are vastly different than they were in history.  The main objective should be to anticipate the future as different from the present, especially given the exponential spreading of the virus.

Another reason why past events should not be considered is increasing global connectivity and the effect it has on the spread of the coronavirus.  As the world becomes more connected, the opportunity for a pathogen to spread globally increases.  A couple of Yaneer’s publications highlight the increased risks of global transportation and studies were undertaken on the effect of “long range connection”.  Yaneer suggested that long range transportation eliminates the opportunity to limit a pathogen to a certain geographic location and effectively kill it, but rather allows it to spread more rapidly and ‘flourish’ somewhere else.  He also presented this subject to the WHO in 2014 and emphasised that what they expected for the future is incorrect.

  • Stopping the coronavirus

Yaneer pointed out that the coronavirus is a “next level risk” because of the combination of how deadly it is, how rapidly it spreads and the period when the symptoms are still unknown.  Consequently, he provided guidance on how to stop the spread of the virus and some of these methods are already visible in various parts of the world.

Firstly, it is important to understand the relevant networks and how they work in order to stop the transmission.  Niall Fergusson mentioned the following in his book The Square and the Tower:  “But that basic reproduction number [how many more people are infected by an individual] of a pandemic is determined as much by the structure of the network it infects, as by the innate infectiousness of the disease”.

The most effective method would thus be to reduce the system to its components and then separate these components.  Yaneer acknowledged that it is known that individuals are isolated and treated but suggests that multi-scale isolation would work best.  Separating the world/countries into regions would stop transmission across boundaries, so that infected regions can be treated and other regions kept safe from infection at the same time.  So effectively a population is isolated and treated at a community scale and not only individual level.  Another important subject is time.  Earlier detection and isolation of both confirmed and potential cases (similar symptoms) is essential.  This can also be promoted by large scale testing and the isolation of all potentially infected individuals.

Yaneer pointed out that both China (even though delayed) and South Korea were able to stop further spreading of the virus through aggressive measures, such as mass testing, transportation shutdown and the lockdown of communities.  Consequently, the spreading shrunk geographically in China and the country appears to be on a trajectory to eliminate the virus.  However, whether such aggressive measures would be deemed appropriate or seen as essential in the West is beyond the scope of this discussion.  Nonetheless, it is quite encouraging to witness large companies and also individuals taking control in the current situation and doing whatever they can to fight this pandemic and support each other while doing so.


Ricard Solé is a research professor at Pompeu Fabra University (UPF), where he is director of the Complex Systems Lab and lectures in biomathematics, biological design and complex diseases.  Other books by him include Phase Transitions and Self-Organization in Complex Ecosystems 

 Santiago F. Elena is professor and head of the Evolutionary Systems Virology Lab at the Spanish National Research Council (CSIC) in Valencia and also an external professor at the Santa Fe Institute.

Yaneer Bar-Yam is the founder and president of the New England Complex Systems Institute.  He received both his B.Sc. and PhD degrees in physics from MIT.


 Solé, R., Elena, S.F., 2018. Viruses as Complex Adaptive Systems. Princeton University Press.