Trends Affecting Pandemic Risk
In recent decades, several trends have affected pandemic probability, preparedness, and mitigation capacity. Various factors—population growth, increasing urbanization, greater demand for animal protein, greater travel and connectivity between population centers, habitat loss, climate change, and increased interactions at the human-animal interface—affect the likelihood of pandemic events by increasing either the probability of a spark event or the potential spread of a pathogen (Tilman and Clark 2014; Tyler 2016; Zell 2004). With global population estimated to reach 9.7 billion by 2050 and with travel and trade steadily intensifying, public health systems will have less time to detect and contain a pandemic before it spreads (Tyler 2016).
As for poverty, the trends are mixed. On the positive side, enormous gains in poverty reduction have decreased the number of people living in extreme poverty. This may attenuate the mortality shock of a mild pandemic somewhat. On the negative side, extreme poverty is now concentrated in a small number of low-growth, high-poverty countries (Chandy, Kato, and Kharas 2015). In such countries, progress in building health system capacity also has been far slower.
Likewise, for a subset of countries with endemically weak institutions, building institutional capacity for complex tasks like pandemic mitigation and response is likely to be a slow process even under the most optimistic assumptions (Pritchett, Woolcock, and Andrews 2013). Many of these countries are in areas with high spark risk, particularly in Central and West Africa, and thus may remain vulnerable and require significant international assistance during a pandemic.
Other environmental and population trends that could increase the severity of pandemics include the persistence of slums, unresponsive health systems, higher prevalence of comorbidities, weaker sanitation, and aging populations (Arimah 2010; UNDESA 2015). The increasing threat posed by antibiotic resistance also could amplify mortality during pandemics of bacterial diseases such as tuberculosis and cholera and even viral diseases (especially for influenza, in which a significant proportion of deaths is often the result of bacterial pneumonia coinfections) (Brundage and Shanks 2008; Van Boeckel and others 2014).