Researchers in Australia have identified the main factors contributing to pandemic vulnerability in cities as growing populations centered around airports and air travel itself, as population growth outpaces the response capabilities of urban infrastructure.

Such were the conclusions reached by a multidisciplinary team led by Australia’s Centre for Complex Systems and the Marie Bashir Institute for Infectious Diseases and Biosecurity. Researchers believe it had exposed vulnerabilities in the nation’s health infrastructure.

“We should be wary of the tendency for local population growth to out-strip the carrying capacity of the urban infrastructure,” Dr. Cameron Zachreson of the Complex Systems Research Group said. “It’s unclear when the next outbreak will be—however our policies should prepare us for crisis situations, such as epidemics, rather than simply keep pace with growth under placid circumstances.”

The research marked the first time scientists in this area turned to anonymous data from the 2006, 2011 and 2016 Australian censuses, using them to forge a simulator to track similarly anonymous households and suburbs. The study of daily interactions granted insight into how diseases spread and how infrastructure can be better prepared against them. Unfortunately, though medical infrastructure has increased over the years, major hospitals are regularly operating at 100 percent capacity, and the effects of influenza — especially Swine flu — have been on the rise since 2009.

“The Australian Census has provided comprehensive data with which to calibrate a nation-level model of pandemic influenza spread and investigate the population’s vulnerability to the contagion over a period of rapid urbanisation,” Mikhail Prokopenko, director of the Complex Systems Research Group, said.

Between 2006 and 2016, Australia’s population increased by 4 million people, especially in urban areas like Sydney and Melbourne. The massive population spike and a near doubling of inbound international flights over the same period has opened the traditionally isolated nation to a greater variety of epidemics.

“We hope that our research can lend strength to the argument that keeping hospital beds at a consistent ratio to the urban population is insufficient and will not account for the relative increases in disease prevalence that our simulation results suggest will occur,” Zachreson said.