Animal-to-human viral epidemics increasing

Death toll could increase 12-fold by 2050.

FOUR TYPES of animal-to-human viral infections have been increasing at an exponential rate, with epidemics becoming larger and more frequent over the past 60 years.

In a study in BMJ Global Health, researchers say that on current trends, zoonotic events are expected to collectively kill 12 times as many people in 2050 as they did in 2020.

The findings come from an analysis of more than 3150 outbreaks and epidemics between 1963 and 2019.

Human-driven changes to climate and land use, as well as population density and connectivity, are predicted to increase the frequency of animal-to-human viral spillover epidemics in the future – that is, zoonotic viruses will more frequently enter the human population. But according to the study, “the magnitude of its implications for global health in the future is difficult to characterise given the limited empirical data on the frequency of zoonotic spillover, and its variability over time”.

So, the researchers – all from Ginkgo Bioworks, a Boston-based biotech company – set out to look for trends in historical spillover events. They focused on four distinct types of viruses with the potential to pose a significant risk to public health, economic, or political stability: filoviruses (such as Ebola and Marburg), SARS coronavirus-1 (which causes SARS), Nipah virus and Machupo virus (which causes Bolivian haemorrhagic fever).

“We find the number of outbreaks and deaths caused collectively by this subset of pathogens have been increasing at an exponential rate from 1963 to 2019,” the team writes.

They identified a total of 75 spillover events that killed 50 or more people, occurring in 24 countries. Together, the events caused 17,232 deaths between 1963 and 2019; 15,771 of these deaths were caused by filoviruses alone.

The team estimates that the number of reported outbreaks has been increasing by about 5% annually, while the number of reported deaths has been increasing by about 9%.

“If the trend observed in this study continues, we would expect these pathogens to cause four times the number of spillover events and 12 times the number of deaths in 2050, compared with 2020,” they write.

“This study suggests the series of recent impactful spillover-driven epidemics are not random anomalies, but follow a multi-decade trend in which epidemics have become both larger and more frequent.

“Concerted global efforts to improve our capacity to prevent and contain outbreaks are urgently needed to address this large and growing risk to global health.”