Animal-to-human infections, or zoonotic diseases, have been increasing at an “exponential rate” and in 2050, are predicted to kill 12 times as many people as they did in 2020, researchers have warned in a new British Medical Journal (BMJ) Global Health study.
Animal-to-human infections, also called ‘spillover’ infections, have been the cause of most modern epidemics, including COVID-19, the researchers from Ginkgo Bioworks, an American biotechnology company founded in 2008, said.
Analysing 60 years of historical epidemiological data, the researchers detected a general pattern of increasingly larger and more frequent spillover events, even as their analysis did not include the ongoing COVID-19 pandemic.
Climate and land use changes are predicted to drive the frequency of spillover events, facilitated by population density and connectivity, the researchers explained.
However, the researchers said that the implications of these findings for future global health are difficult to characterise, given the limited historical data on the annual frequency and severity of zoonotic spillover over time.
Thus, to understand the implications, the researchers drew on their own epidemiological database, built on data from a wide range of official sources, to look for trends in spillover events that might shed light on future expected patterns.
Their database covered epidemics reported by the World Health Organization (WHO), outbreaks caused by a viral pathogen that killed 50 or more people and historically significant outbreaks, such as the 1918 and 1957 flu pandemics.
The researchers focused on four groups of viruses, which, according to them, had the potential to pose a significant risk to public health and economic or political stability – Filoviruses (Ebola virus, Marburg virus), SARS Coronavirus 1, Nipah virus, and Machupo virus, which causes Bolivian hemorrhagic fever.
Looking at over 3150 outbreaks and epidemics between 1963 and 2019, the team identified a total of 75 spillover events occurring in 24 countries. These events had caused a total of 17,232 deaths, more than 90 per cent of which (15,771) across 40 outbreaks – mostly in Africa – were caused by Filoviruses, the researchers found.
Further, the spillover events and reported deaths attributable to these four groups of viruses have been increasing in numbers by almost five and nine per cent, respectively, every year between 1963 and 2019, their analysis found.
“If these annual rates of increase continue, we would expect the analysed pathogens to cause four times the number of spillover events and 12 times the number of deaths in 2050 than in 2020,” the authors write in their study.
They further cautioned that these figures are likely an underestimate for two reasons – exclusion of COVID-19 pandemic and the strict inclusion criteria for the pathogens in the analysis, which effectively ruled out the impact of advances in surveillance and detection over the study period.
The authors acknowledged the “immense value” of measures implemented in response to COVID-19, such as rapid development of mRNA vaccines, passive wastewater testing and active testing, and genomic surveillance to detect emerging variants, in improving resiliency to public health threats.
Still, “the ultimate package of measures to support global prevention, preparedness, and resilience is not yet clear. What is clear, however, from the historical trends, is that urgent action is needed to address a large and growing risk to global health,” conclude the authors.
